Weight loss, in the context of medicine or health or physical fitness, is a reduction of the total body weight, due to a mean loss of fluid, body fat or adipose tissue and/or lean mass, namely bone mineral deposits, muscle, tendon and other connective tissue.

Therapeutic weight loss techniques

Main article: Bariatrics

The least intrusive weight loss methods, and those most often recommended by physicians, are adjustments to eating patterns and increased physical exercise. Usually, health professionals will recommend that their overweight patients combine a reduction of the caloric content of the diet with an increase in physical activity.[6]

Other methods of losing weight include use of drugs and supplements that decrease appetite, block fat absorption, or reduce stomach volume. Surgery is another method. Bariatric surgery artificially reduces the size of the stomach, limiting the intake of food energy. Some of these treatments may have serious side-effects.

Weight loss industry

In the developed world, there is a substantial market for products which promise to make weight loss easier, quicker, cheaper, more reliable, or less painful. These include books, CDs, cremes, lotions, pills, rings and earrings, body wraps, body belts and other materials, fitness centers, personal coaches, weight loss groups and food products and supplements. US residents in 1992 spent an estimated $30 billion a year on all types of diet programs and products, including diet foods and drinks.[7]

Most recently, studies have tended to support that the Carbohydrate restricted diets have a slight edge over the Low-Fat diets. Particularly for men. Women, have a much harder time with weight loss. Even after menopause the female body/metabolism still seems to think that it might get pregnant at any moment, so that any extra calories are turned into fat.

Following any nutrition guide and  you will note that a Gram of Carb and Protein  each have 4kcal/Gram.  Fat has 9 kcal/Gram.

More than twice the energy is stored in Fat. So if you are counting Calories, and trying to restrict your food intake, Fat Calories can quickly add up.

Most weight loss can be easily explained.  If you Burn more Calories than you consume. You will lose weight. How you consume your daily intake of Calories and the proportions of Carbs, Protein, and Fat as well as  your personnel Body Metabolism can have a effect on the success or failure of your short term weight loss, or long term weight loss.

Most of the Popular plans all share some basic concepts.

1. 1.Exercise and Physical Activity should be part of any program.  It has to be fun for the long term so that you can stick with the program. Start off slow and gradually build up. Cardio should be a minimum of 20 minutes. Getting your heart rate up to the optimal rate.  (220-age x 75%).
   

2. 2.Two reasons you are hungry.(a) your stomach is empty.             (b) your blood sugar is low.  Solutions: divide your intake into multiple meals, drink plenty of water, and high fiber/low cal foods will help. This will shrink the size of your stomach.
   

3. 3.Try and include protein with every snack or meal. Carb alone snacks will cause a insulin response and insulin is the key hormone co-factor that causes Lipogenesis(fat production). If you can moderate your insulin response you can minimize fat production. That leads us to a description of Glycemic Index. All carbs are not created equal. Some carbs will increase your blood sugar much higher than others and will create a Insulin response. The higher the Glycemic index of a carb the more it has a tendency to raise your blood sugar. Consume Low Glycemic Index Carbs. A good explanation can be found at:http://www.mendosa.com/gi.htm

   

   
   

Practical Tip

A food is generally considered to have a high GI if it is rated above 60.

Individuals who have problems with maintaining proper blood sugar levels should restrict their selection to foods with a GI of 40 or less. These include those who have low blood sugar (hypoglycemia) and high blood sugar (hyperinsulemia) as well as those who have a high sensitivity to sugar. Sugar includes not just simple sugars, honey and maple syrup but also fruits, fruit juices, starchy vegetables and grain products or foods with a high glycemic index.

For a healthy person without any problems with blood sugar levels all of the foods in a meal do not have to have a low GI. For example, consider a bean-and-cheese filled tortilla. The corn tortilla has a high GI (78), as do pinto beans (GI of 63), but the tomatoes (GI of 15) onions (GI of 15), lettuce (GI of 15) and cheese (GI so low it is not recorded) balance out the overall GI effect. The result is a healthy meal that will not destabilize blood sugar levels.

When planning your healthy GI meals, keep the following simple guidelines in mind:

•Main components should have a GI of no more than 70

•Half of all components should have a GI below 50

References

•Bell SJ, Sears B. Low-glycemic-load diets: impact on obesity and chronic diseases. Crit Rev Food Sci Nutr. 2003;43(4):357-77.

•Brand-Miller, JC. "Glycemic index and obesity." AJCN 76:1, p. 281S-285S, July 2002.

•Brasco, J. Low Grain and Carbohydrate Diets Treat Hypoglycemia, Heart Disease, Diabetes, cancer and Nearly ALL Chronic Illness, www.mercola.com

•Broadhurst CL, Polansky MM, Anderson RA.Insulin-like biological activity of culinary and medicinal plant aqueous extracts in vitro. J Agric Food Chem 2000 Mar;48(3):849-52.

•Foster-Powell, K. et al. "International table of glycemic index and glycemic load value: 2002." AJCN 76:1, p. 5-56, July 2002.

•Goldbeck N, Goldbeck D. The Healthiest Diet in the World, Penguin-Putman: NY, 2001.

•Imparl-Radosevich J, Deas S, Polansky MM, Baedke DA, Ingebritsen TS, Anderson RA, Graves DJ. Regulation of PTP-1 and insulin receptor kinase by fractions from cinnamon: implications for cinnamon regulation of insulin signalling. Horm Res 1998, Sep;50(3):177-82.

•Jenkins, DJA, et al. "Glycemic index: overview of iimplicait5ons in health and disease." AJCN, 76:1, 266S-273S, July 2002.

•Leeds, A.R. "Glycemic Index and heart disease." AJCN 76:1, p. 286S-289S, July 2002.

•Mendosa, R. Revised International Table of Glycemic Index (GI) and Glycemic Load (GL) Values - 2002. www.mendosa.com/gilists.htm

•Pi-Sunyer, FX. "Glycemic index and disease." AJCN 76:1, p. 290S-298S, July 2002.

•Willett, W. "Glycemic index, glycemic load and risk of type 2 diabetes." AJCN 76:1, p. 274S-280S, July 2002.

1. •Wolever, T. The Glycemic Index: Flogging a Dead Horse? Diabetes Care, 20:3, p 452-456, 1997.
   

4. 4.     The Metabolic Advantage:  Dr.Atkins, Popularized the concepts of a Carbo restricted diet.  Studies over the past ten years have demonstrated the success of this type of diet. Unfortunately many people do not understand the concepts of transitioning to a Maintenance carb reduced diet as part of a long term diet plan. If you go back your old life style you will gain the weight back and then as the rebound effect has demonstrated, usually you will gain more back. The key for most individuals is find out how many grams of Carb you can consume a day in order to maintain your weight. On the initial stage of the Atkins’ diet if you can keep you carb intake below 20 grams a day, your body will go into Ketosis. That means your body will start to burn Fat,”Lipolysis”. Your brain and nervous system can function fine for extended periods of time in Ketosis. Most people will find that after 3-4 days they will have decreased appetite. The trick of the carb reduced diet is to figure out how many carbs you can consume and not come our of ketosis.                                                           
   

5. 5.      Transitioning to a long term plan that works for you is the key to long term results. Maintaining a active lifestyle and exercise plan for life is the key to long term success.   
   

The Atkins Diet restricts "net carbs" (carbohydrates that have an effect on blood sugar). One effect is a tendency to decrease the onset of hunger, perhaps due to longer duration of digestion (fats and proteins take longer to digest than carbohydrates). Dr. Atkins says in Dr. Atkins' New Diet Revolution (2002) that hunger is the number one reason why low-fat diets fail. Though studies show the efficacy of the Atkins approach after one year is the same as some low-fat diets, Dr. Atkins claimed that it was easier to stay on the Atkins diet because dieters did not feel as hungry or "deprived".[citation needed]

Net carbohydrates can be calculated from a food source by subtracting fiber and sugar alcohols (which are shown to have a negligible effect on blood sugar levels) from total carbohydrates. Sugar alcohols need to be treated with caution, because while they may be slower to convert to glucose, they can be a significant source of glycemic load and can stall weight loss. Fructose (eg, as found in many industrial sweeteners) also contributes to caloric intake, though outside of the glucose-insulin metabolic control loop.

Induction

The Induction phase is the first, and most restrictive, phase of the Atkins Nutritional Approach. Two weeks are recommended for this phase. It is intended to cause the body to quickly enter a state of ketosis. Carbohydrate intake is limited to 15-20 net grams per day (grams of carbohydrates minus grams of fiber, sugar alcohols, or glycerin), 12 to 15 net grams of which must come in the form of salad greens and other green vegetables (broccoli, green beans, spinach and asparagus). The allowed foods include a liberal amount of all meats, poultry, fish, shellfish, fowl, and eggs; up to 4 ounces (113 g) of soft or semi-soft cheese such as cheddar cheese; salad vegetables; other low carbohydrate vegetables; and butter, olive oil and vegetable oils. Drinking eight glasses of water per day is a must during this phase. Alcoholic beverages are not allowed during this phase.[5] Caffeine is allowed in moderation so long as it does not cause cravings or low blood sugar. If a caffeine addiction is evident, it is best to not allow it until later phases of the diet.[5] A daily multivitamin with minerals, except iron, is also recommended.

The Induction Phase is usually when many see the most significant weight loss — reports of losses of 5 to 10 pounds per week are not uncommon when Induction is combined with daily exercise.

Atkins suggests the use of Ketostix, small chemically reactive strips used by diabetics. These let the dieter monitor when they enter the ketosis, or fat burning, phase. Other indicators of ketosis include a metallic taste in the mouth, or bad breath

Ongoing weight loss

The Ongoing Weight Loss (OWL) phase of Atkins consists of an increase in carbohydrate intake, but remaining at levels where weight loss occurs. The target daily carbohydrate intake increases each week by 5 net grams. A goal in OWL is to find the "Critical Carbohydrate Level for Losing" and to learn in a controlled manner how food groups in increasing glycemic levels and foods within that group affect your craving control. The OWL phase lasts until weight is within 10 pounds (4.5 kg) of the target weight.

During the first week, one should add more of the induction acceptable vegetables to his/her daily products. For example, 6-8 stalks of asparagus, salad, one cup of cauliflower or one half of avocado. The next week, one should follow the carbohydrate ladder that Dr Atkins created for this phase and add fresh dairy. The ladder has 9 rungs and should be added in order given. One can skip a rung if one does not intend to include that food group in one's permanent way of eating, such as the alcohol rung.

The rungs are as follows:

▪Induction acceptable vegetables

▪Fresh dairy

▪Nuts

▪Berries

▪Alcohol

▪crisps

▪Other fruits

▪Starchy vegetables

▪Grains

Pre-maintenance

Carbohydrates intake is increased again this time by 5 net carbs a week from the ladder groupings, and the key goal in this phase is to find the "Critical Carbohydrate Level for Maintenance", this is the maximum number of carbohydrates you can eat each day without gaining weight. This may well be above the level of carbohydrates inducing ketosis on a testing stick. As a result, it is not necessary to maintain a positive ketosis test long term.

Lifetime maintenance

This phase is intended to carry on the habits acquired in the previous phases, and avoid the common end-of-diet mindset that can return people to their previous habits and previous weight. Whole, unprocessed food choices are emphasized, with the option to drop back to an earlier phase if you begin to gain weight.

Here is a link to a video clip on the NEJ of M paper on MSNBC

http://www.msnbc.msn.com/id/3032619/vp/25706130#25706130

The new england 

journal of medicine

established in 1812 july 17, 2008 vol. 359 no. 3

Weight Loss with a Low-Carbohydrate, Mediterranean, 

or Low-Fat Diet

Iris Shai, R.D., Ph.D., Dan Schwarzfuchs, M.D., Yaakov Henkin, M.D., Danit R. Shahar, R.D., Ph.D., 

Shula Witkow, R.D., M.P.H., Ilana Greenberg, R.D., M.P.H., Rachel Golan, R.D., M.P.H., Drora Fraser, Ph.D., 

Arkady Bolotin, Ph.D., Hilel Vardi, M.Sc., Osnat Tangi-Rozental, B.A., Rachel Zuk-Ramot, R.N., 

Benjamin Sarusi, M.Sc., Dov Brickner, M.D., Ziva Schwartz, M.D., Einat Sheiner, M.D., Rachel Marko, M.Sc., 

Esther Katorza, M.Sc., Joachim Thiery, M.D., Georg Martin Fiedler, M.D., Matthias Blüher, M.D., 

Michael Stumvoll, M.D., and Meir J. Stampfer, M.D., Dr.P.H., 

for the Dietary Intervention Randomized Controlled Trial (DIRECT) Group

N Engl J Med 2008;359:229-41.

Copyright © 2008 Massachusetts Medical Society.

Background

Trials comparing the effectiveness and safety of weight-loss diets are frequently

limited by short follow-up times and high dropout rates.

Methods

In this 2-year trial, we randomly assigned 322 moderately obese subjects (mean age,

52 years; mean body-mass index [the weight in kilograms divided by the square of the

height in meters], 31; male sex, 86%) to one of three diets: low-fat, restricted-calorie;

Mediterranean, restricted-calorie; or low-carbohydrate, non–restricted-calorie.

Results

The rate of adherence to a study diet was 95.4% at 1 year and 84.6% at 2 years. The

Mediterranean-diet group consumed the largest amounts of dietary fiber and had the

highest ratio of monounsaturated to saturated fat (P<0.05 for all comparisons among

treatment groups). The low-carbohydrate group consumed the smallest amount of car-

bohydrates and the largest amounts of fat, protein, and cholesterol and had the highest

percentage of participants with detectable urinary ketones (P<0.05 for all comparisons

among treatment groups). The mean weight loss was 2.9 kg for the low-fat group, 4.4

kg for the Mediterranean-diet group, and 4.7 kg for the low-carbohydrate group (P<0.001

for the interaction between diet group and time); among the 272 participants who com-

pleted the intervention, the mean weight losses were 3.3 kg, 4.6 kg, and 5.5 kg, respec-

tively. The relative reduction in the ratio of total cholesterol to high-density lipoprotein

cholesterol was 20% in the low-carbohydrate group and 12% in the low-fat group

(P = 0.01). Among the 36 subjects with diabetes, changes in fasting plasma glucose and

insulin levels were more favorable among those assigned to the Mediterranean diet than

among those assigned to the low-fat diet (P<0.001 for the interaction among diabetes

and Mediterranean diet and time with respect to fasting glucose levels).

Conclusions

Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat

diets. The more favorable effects on lipids (with the low-carbohydrate diet) and on

glycemic control (with the Mediterranean diet) suggest that personal preferences

and metabolic considerations might inform individualized tailoring of dietary in-

terventions. (ClinicalTrials.gov number, NCT00160108.)

Monday, Jul. 28, 2008

The Myth of Moderate Exercise

By Laura Blue

Obesity experts agree that daily exercise is essential for good health, but whether it can successfully lead to long-term weight loss is a question of much debate. What has become increasingly clear, however, is that the conventionally accepted advice — 30 minutes of moderate-intensity activity most days of the week — is probably insufficient to spur any real change in a person's body weight. A study published July 28 in the Archives of Internal Medicine adds to the burgeoning scientific consensus: when it comes to exercise for weight loss, more is better. It suggests that obese people would have to exercise at least an hour at a time to see any significant difference in their weight.

The study, led by John Jakicic at the Physical Activity and Weight Management Research Center at the University of Pittsburgh, followed nearly 200 overweight or obese women ages 21 to 45 through a two-year weight-loss program. The women were given free treadmills to use at home, regular group meetings and telephone pep talks to help keep them on track. Participants were also asked to restrict their food intake to between 1,200 and 1,500 calories per day, and were randomized to one of four physical activity intervention groups based on energy expenditure (either 1,000 calories or 2,000 calories burned per week) and exercise intensity (high vs. moderate). By the end of the 24-month intervention, the women who managed to lose at least 10% of their starting body weight (which was, on average, about 193 lbs.) — and keep it off — were exercising twice as long as health authorities typically recommend and expending more than twice as many calories through exercise as women who had no change in body weight. The biggest weight losers were active a full 68 minutes a day, five days a week (about 55 minutes a day more than they had been before the trial began), burning an extra 1,848 calories a week.

Jakicic and his colleagues originally designed their study to measure whether weight loss could really be achieved and maintained through moderate-intensity exercise, akin to "walking when you're late for a meeting," he says, or whether it was preferable to engage in shorter bursts of more vigorous-intensity activity, "like, when you're late for the bus, chasing it down." The problem was that not enough of the women stuck with their assigned exercise categories for the researchers to gather enough meaningful data. Within a few months, most of the participants had resorted to exercising as much as they chose to. That left researchers with a slightly different data set than they had planned for, but they were still able to associate women's reported physical activity with their weight loss. Indeed, exercise was more strongly associated with weight loss than any other factor, including diet. Overall, the more the women exercised, the more weight they lost.

More than half of the study participants managed to lose at least 10% of their body weight within the first six months. At the half-year mark, however, most of those women relapsed and started gaining the weight back — a discouragingly common phenomenon. "The major outcome of this paper is the maintenance issue," Jakicic says. Once a patient hits her target weight, he says, it's imperative that she stick with her exercise and diet regimen to maintain her new weight.

Still, the underlying question remains: are diet and exercise a reliable cure for obesity? Modern-day obesity researchers are skeptical — achieving thinness, they say, is not simply a matter of willpower. Research suggests that weight may largely be regulated by biology, which helps determine the body's "set point," a weight range of about 10 lbs. to 20 lbs. that the body tries hard to defend. The further you push you weight beyond your set point — either up or down the scale — some researchers say, the more your body struggles to return to it. That might help to explain why none of the women in Jakicic's study managed to lose much more than 10% of their body weight. After two years on a calorie-restricted diet, keeping up more than an hour of physical activity five days a week on average, most were still clinically overweight (though much less so than before). But what Jakicic and other obesity researchers stress is that a 10% reduction in body weight represents a tremendous boon for overall well-being, lowering blood pressure, improving heart health and reducing the risk of Type 2 diabetes. For the obese, the end goal should not be thinness, but health and self-acceptance, which are more realistic and beneficial objectives. "The women's health was absolutely improved," Jakicic says.

Jakicic, in fact, seems heartened by his findings. "I think the beauty of this study is that we now have a target" — a better idea of how much exercise is needed for weight maintenance. There is, of course, some variation in how people respond. Some of the study participants fared well with less exercise than the additional 275 minutes per week (about 55 minutes per day, five days a week) that the study's author now recommends for weight maintenance. Others needed more. But the keys to success, according to Jakicic, were embracing the weight-loss program fully, and finding a way around the daily obstacles to exercising — that's something he says many of his participants were able to achieve, regardless of their socioeconomic group. So, if you're aiming to lose weight and keep it off, his message is clear: don't slack off.

In physics, mechanical work is the amount of energy transferred by a force. Like energy, it is a scalar quantity, with SI units of joules. The term work was first coined in the 1830s by the French mathematician Gaspard-Gustave Coriolis.[1]

According to the work-energy theorem if an external force acts upon an object, causing its kinetic energy to change from Ek1 to Ek2, then the mechanical work (W) is given by:[2]

where m is the mass of the object and v is the object's speed.

The mechanical work applied to an object can be calculated from the dot product of the applied force (F) and the displacement (d) of the object. This is given by:   work = F x Distance

F= Mass (weight) X g (gravity)            G= 9.8  m/s  squared.

▪1 International Table calorie = 4.1868 J

▪1 watt hour = 3600 J

▪1 kilowatt hour = 3.6 ×106 J (or 3.6 MJ)

▪1 ton TNT = 4.184 GJ

Useful to remember:

▪1 joule = 1 newton meter = 1 watt second

When you lift weights the calories burned are equivalent to the Joules expended,  I cal= 4.1 joule

Bottom line:  THE MORE WEIGHT YOU MOVE, THE GREATER NUMBER OF REPETITIONS, THE  GREATER THE WORK YOU WILL EXPENDED AND THE MORE CALORIES YOU WILL HAVE BURNED.

1 Joule is roughly the amount of energy required to lift a 1 kilo object 10 cm=1 meter off the ground.

You need to understand that the "energy" in this sense is not necessarily the energy you might burn in your muscles since there is a lot from the small muscles pulling against each other, etc. In particular, it does not take any energy at all to hold a heavy object at a constant height off the ground, any more than a table uses energy to hold an object there. The tiredness you feel after trying to hold up a heavy object for a long time is not energy imparted to the object but the result of the fact that your muscles are not 100% efficient and is not counted in mechanics.

Actually, the " energy required to lift a 1 kilo object 10 cm of the ground" is a good approximation to a Joule but not exactly true. Two equivalent definitions of the "Joule" are "the work done by a 1 Newton force in moving an object 1 meter" and "the kinetic energy of a 1 kg object moving at 1 meter per second". Since a Newton is defined as "the force necessary to accelerate a 1 kg object at 1 meter per second per second", it has basic units of kg m/s2 and so, multiplying by that "1 meter", a Joule has basic units of kg m2/s2. Kinetic energy, on the other hand is (1/2)mv2 and so has basic units of "kg times (meter per second squared)" or kg(m2/s2 just as before.

Since the acceleration due to gravity at the surface of the earth is about 9.8 m/s2, the weight of a 1 kg object is 1(9.8)= 9.8 Newtons= 9.8 kg m/s2 and so lifting it 10 cm= 0.1 m you have done work (imparted energy to the object) of (0.1 cm)(9.8 kg m/s2)= 0.98 kg m2/s2= 0.98 Joules, not exactly one Joule.

Weight loss and exercise: What works and what doesn't?

This article is biased.

It is heavily influenced by my experience as a personal trainer in the early 1990's. During that time, I saw literally hundreds of people try — and fail — to speed up weight loss with a program of regular aerobic exercise.

By aerobic exercise, I mean things like cycling, walking, rowing or jogging, usually performed for between 20 and 60 minutes in the so-called "aerobic training zone." Interval exercise, on the other hand, especially when you get the length of the work and rest intervals right, is another story entirely.

Despite what we've been told, aerobic exercise has very little effect on weight loss. There's been enough research over the last 25 years to convince almost anyone that aerobic exercise programs are not a very effective way to promote weight loss.

Weight loss

Most people begin an exercise program designed for weight loss with the intention of sticking with it. Unfortunately, the majority give up after six months, deciding they simply don't have the time to exercise regularly.

There are usually two reasons behind any decision — the real reason, and the one that sounds good! Individuals claiming, "they don't have the time" are often hiding the fact that their expectations were not met. Simply put, they were not making the progress they were promised. For many people, the benefits of aerobic exercise are not enough to justify the time and effort you put in.

On an intellectual level, most people know they "should do more exercise." However, any good salesperson will tell you that we don't make decisions based on intellectual reasoning. We base them on emotion.

Most of us exercise because, at a very basic level, we want to look and feel better. We exercise because it appeals to our sense of vanity and pride. We want to look and feel good.

The problem comes when there is a conflict between the results you expect from aerobic exercise, and what you actually get. Many people starting an exercise program are told they can expect to lose around two pounds of fat each week.

Some people do. But the majority doesn't.

It's easy to think the problem lies with you. Is it because your metabolism is slow? Are you getting older and burning calories at a slower rate? Is it in your genes? You stick to the program, and still you don't lose any weight.

What's going on?

Although it comes as a surprise to many, the majority of research shows that aerobic exercise has only a minor effect on weight loss.

Some evidence for this comes from a review of several hundred weight loss studies conducted by Dr. Wayne Miller and colleagues at The George Washington University Medical Center [5].

The team examined 493 studies carried out between 1969 and 1994. Miller and his associates wanted to determine whether adding aerobic exercise to a low-calorie diet accelerates weight loss. Twenty-five years of weight loss research shows that diet and aerobic exercise provides only a very marginal benefit (in terms of weight loss) when compared to diet alone.

The average weight loss after a 15-week program of regular aerobic exercise was seven pounds. Over the same period, dieting cut weight by roughly 17 pounds. When exercise and diet were combined, average weight loss was 20 pounds — just three pounds more than diet alone.

A study completed at Appalachian State University also shows that aerobic exercise has little effect on body composition over a 12-week period [7].

The research team assigned a group of 91 obese women to one of four groups. Group one followed a restricted calorie diet (1,200 - 1,300 calories per day), while group two performed aerobic exercise for 45 minutes, five days each week. A third group combined exercise and diet. The fourth group acted as controls.

The exercise-only group lost just three pounds. This is despite the fact they were exercising for almost four hours each week. Not surprisingly, the women combining diet and exercise got the best results, losing 16 pounds of fat. However, this was only one pound more than the group on the diet. These disappointing results led the researchers to conclude that aerobic exercise has only a "minor, nonsignificant effect" on fat loss.

A study at Pennsylvania State University shows similar results [10]. A group of men took part in a 12-week program of diet and exercise. Half the men dieted, while the rest used a combination of diet and aerobic exercise. Despite the fact they trained three times each week for up to 50 minutes (under the watchful eye of certified personal trainers), the exercise and diet group lost only one pound more fat than the diet-only group.

Research carried in the Journal of Applied Physiology also shows that aerobic exercise has a minor effect on fat loss [21].

A group of 24 obese men was assigned to either a low- or high-intensity exercise group for 12 weeks. The men were told to maintain their dietary habits during the study.

The exercise program consisted of cycling at either low-intensity (40% VO2max) or high-intensity (70% VO2max) three times per week. Each workout burned about 350 calories. The duration of each workout for subjects in the low-intensity and high-intensity training program was 57 and 33 minutes, respectively.

After analyzing the results, the researchers conclude that exercise training "did not lead to significant changes in body weight and body composition."

Aerobic exercise again failed to deliver any meaningful results when the training frequency was increased to five times per week. A team of Canadian researchers, publishing their findings in the Journal of Applied Physiology, followed a group of men and women for four months [16]. Half the group followed a restricted calorie diet, while the rest combined the diet with five days a week of cross training (a mixture of treadmill walking, cycling and stepping).

At the end of the program, scientists were at a loss to explain why the diet and exercise group had lost just one-half pound more than the diet-only group, describing their findings as "perplexing".

In one 1997 study carried in the journal Medicine and Science in Sports and Exercise, group of adult males lost just four pounds in weight — despite three hours of exercise every week for 14 weeks [11]. Hardly the dramatic results we're promised when joining a gym.

Many people believe they need to spend six hours or more in the gym each week to get the results they're looking for [9]. And it's true that for aerobic exercise to be effective, you need to do a lot of it. Scientists from Canada report that three months of aerobic exercise was enough to cut body fat levels by an average of 13 pounds [15]. However, the brave souls who volunteered for this study trained for more than one hour, every single day, for three whole months.

Personally, all that aerobic exercise would bore me silly. The exercise program I use to shed fat requires that I spend no more than five hours in the gym each week. It's virtually identical to the program you'll read about elsewhere on this site. That's not because I'm lazy. It's just that I don't have the time (or the motivation) for the marathon workouts that all the "experts" tell me I need.

One of the main criticisms of weight loss studies is the small number of participants they use. The more people that take part in a study, the more reliable the results. The challenge for researchers is trying to stop people dropping out. When a research group from the University of Georgia attempted to examine the effect of aerobic exercise on fat loss, more than half the subjects quit before the study was finished [12]!

This shouldn't come as a surprise, especially when you consider the fact most subjects make such little progress.

In an attempt to make their study more reliable, researchers designed the HERITAGE Family Study, describing it as the largest, well-controlled training study of its kind [13]. A large group of 557 men and women was followed as they embarked on a 20-week exercise program.

Each subject was required to exercise three times per week for an average of 42 minutes. Researchers even went to the trouble of having each bout of exercise monitored by an exercise technician and a computer. Following a grand total of 60 exercise sessions over a period of almost six months, the average amount of fat lost was slightly less than two pounds, prompting scientists to admit that aerobic exercise "is not a major factor" in weight loss.

Calorie counters

This isn't surprising when you consider how many calories are contained in a pound of fat — the equivalent of roughly 3,555 calories. The most fundamental aspect of any fat loss program is to create a calorie deficit — to burn more calories than you eat. Unfortunately, aerobic exercise burns around 187 calories per session [7]. Based on this estimate, you'll need 19 workouts, each lasting 45 minutes, to lose just one pound of fat.

This figure might come as a surprise if you use the calorie counters on exercise machines to monitor calorie expenditure during a workout. Unfortunately, these digital readouts are not always accurate. The most reliable way to assess energy expenditure during exercise is to measure oxygen consumption. Each liter of oxygen that you consume generates approximately five calories of energy.

For example, if you exercise for 30 minutes and consume 30 liters of oxygen, you'll have burned 150 calories. Without directly measuring oxygen consumption, it's difficult to get an accurate estimate of energy expenditure during a workout.

Another factor that affects the reliability of calorie counters is the difference between net and gross calorie expenditure. Gross energy expenditure refers to the number of calories you burn during exercise plus your metabolic rate. Net energy expenditure refers to just the number of calories you burn during exercise.

Because calorie counters on some (but not all) exercise machines display gross energy expenditure, the figures they give can be misleading.

A good example comes from a trial carried in the International Journal of Sport Nutrition [7]. A group of overweight women took part in an aerobic exercise program. The program involved 45 minutes of aerobic exercise, performed in the so-called aerobic training zone (70-80% of maximum heart rate).

The average number of calories burned during each workout was estimated to be 255 calories. However, this figure doesn't take into account the difference between net and gross caloric expenditure.

The gross number of calories burned was 255. In contrast, the net figure (remember, the net figure represents the "real" number of extra calories you've burned) was just 187 calories. In other words, if you rely on the numbers given by the calorie counters, it might appear that you've burned more calories than you really have.

Muscle loss

When you lose weight from dieting alone, some of the weight lost comes from lean muscle tissue. Some experts believe that aerobic exercise prevents this reduction in muscle mass. But the facts tell a different story. Several studies show that diet and aerobic exercise both lead to a drop in muscle tissue [10, 15]. Aerobic exercise won't offset the loss in lean muscle caused by dieting.

When you lose weight by dieting, roughly seven of every 10 pounds lost over a 12-week period come from fat. Adding aerobic exercise doesn't prevent the loss of muscle. But it does reduce it slightly. You'll get better results when you combine the right diet with aerobic exercise and resistance training. Virtually all of the weight you lose with this kind of program will come from fat [10].

One popular claim is that aerobic exercise leads to an increase in your metabolic rate. However, researchers conducting the HERITAGE Family Study found that almost six months of aerobic exercise has no effect on resting metabolic rate [13].

Some studies do show that elite athletes do have a higher metabolic rate than weight-matched controls. However, scientists have been unable to establish whether this is due to a high calorie intake, a superior level of fitness or if it exists simply as an after effect of their last training session [6]. Furthermore, when an increase in physical activity results in a calorie deficit, there is evidence to show that the metabolic rate does not rise at all [6, 14].

Another popular misconception is the idea that aerobic exercise increases caloric expenditure after a bout of exercise, thus making a further contribution to fat loss. Unfortunately this is not always the case. Excess post-exercise oxygen consumption (the name given to the increase in caloric expenditure following a workout) is more likely to occur after high-intensity exercise. Moderate-intensity aerobic exercise (such as walking or jogging) has very little effect on post-exercise metabolic rate.

Does this mean that aerobic exercise is a waste of time? Definitely not.

Weight gain

There is evidence to show that aerobic exercise helps to prevent the gain in weight that often happens following a period of dieting [2]. It's extremely difficult to stick to the kind of diet needed to maintain weight loss. As a result, many people soon return to their original weight.

Aerobic exercise plays a vital role in helping you maintain a healthy body weight. The National Weight Control registry contains a listing of subjects who have lost at least 30 pounds of weight, and kept it off for at least 12 months.

Although the people on the register use a number of different strategies to reduce body fat, the one thing they have in common is a commitment to regular exercise [4]. Scientists from George Washington University also report that regular exercise helps to maintain higher levels of weekly fat loss 12 months after starting a diet [5].

Researchers at Maastricht University have shown that just ten weeks on a very low-calorie diet actually reduces the number of fat calories your body burns each day [8]. This post-diet drop in fat oxidation could explain why many people find it difficult to stop the weight coming back once they've lost it.

A group of 40 overweight men took part in the study. They were assigned to one of two groups. One group dieted, while group two combined the diet with a program of regular aerobic exercise. The men in the exercise group completed three sessions per week, consisting of walking and underwater exercise. Each workout lasted for around one hour.

During the first six weeks of the study, subjects in both groups were given a very low-calorie diet providing just 500 calories daily. From weeks 7 to 10, they gradually increased their food intake.

Both groups lost roughly the same amount of fat and muscle. However, the subjects who didn't exercise had a reduced capacity to burn fat, both at rest and during exercise. The good news is that exercise served to prevent this decline.

What this means is that the benefits of low-intensity aerobic exercise are more apparent when you're trying to keep the weight off. The exercise doesn't have to be particularly vigorous or demanding. Just three hours of walking each week is enough to prevent the post-diet decline in fat oxidation.

Physical activity as part of a fat loss strategy also appears to encourage healthier eating patterns. Individuals who exercise frequently may perceive food as "activity fuel", and place greater importance on the quality of their diet.

Californian researchers have identified a direct link between physical activity and various markers of dietary quality [3]. They found that physical activity was associated with healthy eating habits, such as eating fruit and vegetables. More physically active individuals are also less likely to eat foods with a high calorie content.

That said, there are also people who eat what they want, then do hours and hours of exercise in an attempt to burn it off again. This is mistake. When it comes to shedding fat while preserving lean muscle, one of the most important hormones is testosterone. Although testosterone is considered a muscle-building hormone, there are studies showing that it also helps to cut body fat.

Unfortunately, too much exercise can lower testosterone. Endurance-trained men, for example, have lower testosterone levels than men of the same age who never exercise [19]. Men with low testosterone levels are also more likely to develop a pot belly [17].

In short, trying to make up for a poor diet by doing a lot of aerobic exercise is not a good idea.

Subcutaneous fat

Publishing their findings in Medicine and Science in Sports and Exercise, Japanese researchers have shown that dieting leads to a greater reduction in visceral fat [1]. Exercise, on the other hand, has a greater impact on subcutaneous fat. Subcutaneous fat (pronounced sub-cue-tain-ee-us) is stored just under your skin. Visceral fat (pronounced viss-er-al) surrounds and protects your internal organs.

The women in the study took part in a 13-week program that combined exercise with a restricted-calorie diet. One group followed the diet, combined with 1-2 days per week of exercise. Group two made no change to their diet, but exercised 3-4 days each week.

Both groups lost roughly the same amount of fat. In the group who exercised more frequently, six of every 10 pounds of fat lost came from subcutaneous fat. However, in the group who exercised less frequently, less than three of every 10 pounds of fat lost came from subcutaneous fat.

Energy flux

Aerobic exercise also allows for a higher energy flux, which refers to the flow of calories (or energy) through your body.

A high energy flux means that you're eating a large number of calories, but balancing that with an equally high volume of exercise. A good example of someone with a high energy flux would be a cyclist taking part in the Tour de France. Despite the fact these athletes eat thousands of calories each day, they're still able to remain lean simply because they're doing so much exercise.

An example of a low energy flux would be someone following an extremely low-calorie diet while doing little or no exercise.

A high energy flux is linked with a high metabolic rate. Endurance-trained males, for example, in a high state of energy flux have a higher metabolic rate compared with a low energy flux state.

As they age, people are generally less physically active. The result is that they burn fewer calories each day. Unless they eat less to compensate for this reduction in calorie expenditure, weight gain is the inevitable result.

The good news is that you can minimize the age-related drop in basal metabolic rate by maintaining a high energy flux — balancing a higher calorie intake with an equally high volume of exercise. Not only will this help you to stay lean, it's also a great way to provide your body with more of the vitamins, minerals and other nutrients it needs.

The bottom line

Many people starting an exercise program are told they can expect to lose around two pounds of fat each week. Some people do. However, the majority doesn't.

It's easy to think the problem lies with you. Is it because your metabolism is slow? Are you getting older and burning calories at a slower rate? Is it in your genes? You stick to the program, and still you don't lose any weight.

Although it comes as a surprise to many, the majority of research shows that aerobic exercise — such as waking, jogging, cycling or rowing — in the so-called "aerobic training zone" is not a very effective way to lose fat.

At best, you can expect to lose between one-quarter and one-half pound of fat per week, depending on how much aerobic exercise you do.

Regular exercise is important because it promotes the loss of subcutaneous fat. Subcutaneous fat is stored just under your skin. Visceral fat surrounds and protects your internal organs.

Aerobic exercise also allows for a higher energy flux, which refers to the flow of calories (or energy) through your body. This lets you balance a higher calorie intake with an equally high volume of exercise. Not only will this help you to stay lean, it's also a great way to provide your body with the vitamins, minerals and other nutrients it needs.

References
1. Abe, T., Kawakami, Y., Sugita, M., & Fukunaga, T. (1997). Relationship between training frequency and subcutaneous and visceral fat in women. Medicine and Science in Sports and Exercise, 29, 1549-1553
2. Buemann, B., & Tremblay, A. (1996). Effects of exercise training on abdominal obesity and related metabolic complications. Sports Medicine, 21, 191-212
3. Johnson, M.F., Nichols, J.F., Sallis, J.F., Calfas, K.J., & Hovell, M.F. (1998). Interrelationships between physical activity and other health behaviors among University women and men. Preventive Medicine, 27, 536-544
4. McGuire, M.T., Wing, R.R., Klem, M.L., Seagle, H.M., & Hill, J.O. (1998). Long-term maintenance of weight loss: do people who lose weight through various weight loss methods use different behaviors to maintain their weight? International Journal of Obesity, 22, 572-577
5. Miller, W.C., Koceja, D.M., & Hamilton, E.J. (1997). A meta analysis of the past 25 years of weight loss research using diet, exercise or diet plus exercise intervention. International Journal of Obesity, 21, 941-947
6. Sjodin, A.M., Forslund, A.H., Westerterp, K.R., Andersson, A.B., Forslund, J.M., & Hambraeus, L.M. (1996). The influence of physical activity on BMR. Medicine and Science in Sports and Exercise, 28, 85-91
7. Utter, A.C., Nieman, D.C., Shannonhouse, E.M., Butterworth, D.E., & Nieman, C.N. (1998). Influence of diet and/or exercise on body composition and cardiorespiratory fitness in obese women. International Journal of Sport Nutrition, 8, 213-222
8. van Aggel-Leijssen, D.P.C., Saris, W.H.M., Hul, G.B., & van Baak, M.A. (2001). Short-term effects of weight loss with or without low-intensity exercise training on fat metabolism in obese men. American Journal of Clinical Nutrition, 73, 523-531
9. Timperio, A., Cameron-Smith, D., Burns, C., Salmon, J., & Crawford, D. (2000). Physical activity beliefs and behaviours among adults attempting weight control. International Journal of Obesity, 24, 81-87
10. Kraemer, W.J., Volek, J.S., Clark, K.L., Gordon, S.E., Puhl, S.M., Koziris, L.P., McBride, J.M., Triplett-McBride, N.T., Putukian, M., Newton, R.U., Hakkinen, K., Bush, J.A., & Sebastianelli, W.J. (1999). Influence of exercise training on physiological and performance changes with weight loss in men. Medicine and Science in Sports and Exercise, 31, 1320-1329
11. Wallace, M.B., Mills, B.D., & Browning, C.L. (1997). Effects of cross training on markers of insulin resistance/hyperinsulinemia. Medicine and Science in Sports and Exercise, 29, 1170-1175
12. Evans, E.M., Saunders, M.J., Spano, M.A., Arngrimsson, S.A., Lewis, R.D., & Cureton, K.J. (1999). Body-composition changes with diet and exercise in obese women: a comparison of estimates from clinical methods and a 4-component model. American Journal of Clinical Nutrition, 70, 5-12
13. Wilmore, J.H., Despres, J.P., Stanforth, P.R., Mandel, S., Rice, T., Gagnon, J., Leon, A.S., Rao, D.C., Skinner, J.S., & Bouchard, C. (1999). Alterations in body weight and composition consequent to 20 wk of endurance training: the HERITAGE Family Study. American Journal of Clinical Nutrition, 70, 346-352
14. Bullough, C.R., Gilette, C.A., Harris, M.A., & Melby, C.L. (1995). Interaction of acute changes in exercise energy expenditure and energy intake on resting metabolic rate. American Journal of Clinical Nutrition, 61, 473-481
15. Ross, R., Dagnone, D., Jones, P.J.H., Smith, H., Paddags, A., Hudson, R., & Janssen, I. (2000). Reduction in obesity and related comorbid conditions after diet-induced weight loss or exercise-induced weight loss in men. Annals of Internal Medicine, 133, 92-103
16. Ross, R., Rissanen, J., Pedwell, H., Clifford, J., & Shragge, P. (1996). Influence of diet and exercise on skeletal muscle and visceral adipose tissue in men. Journal of Applied Physiology, 81, 2445-2455
17. Tsai, E.C., Boyko, E.J., Leonetti, D.L., & Fujimoto, W.Y. (2000). Low serum testosterone level as a predictor of increased visceral fat in Japanese-American men. International Journal of Obesity and Related Metabolic Disorders, 24, 485-491
18. Epel, E.S., McEwen, B., Seeman, T., Matthews, K., Castellazzo, G., Brownell, K.D., Bell, J., & Ickovics, J.R. (2000). Stress and body shape: stress-induced cortisol secretion is consistently greater among women with central fat. Psychosomatic Medicine, 62, 623-632
19. Hackney, A.C., Szczepanowska, E., & Viru, A.M. (2003). Basal testicular testosterone production in endurance-trained men is suppressed. European Journal of Applied Physiology, 89, 198-201
20. Jacks, D.E., Sowash, J., Anning, J., McGloughlin, T., & Andres, F. (2002). Effect of exercise at three exercise intensities on salivary cortisol. Journal of Strength and Conditioning Research, 16, 286-289
21. van Aggel-Leijssen, D.P., Saris, W.H., Wagenmakers, A.J., Senden, J.M., & van Baak, M.A. (2002). Effect of exercise training at different intensities on fat metabolism of obese men. Journal of Applied Physiology, 92, 13

How to make muscle GROW=  MUSCULAR HYPERTROPHY

April 12, 2010

Weighing the Evidence on Exercise

By GRETCHEN REYNOLDS

How exercise affects body weight is one of the more intriguing and vexing issues in physiology. Exercise burns calories, no one doubts that, and so it should, in theory, produce weight loss, a fact that has prompted countless people to undertake exercise programs to shed pounds. Without significantly changing their diets, few succeed. “Anecdotally, all of us have been cornered by people claiming to have spent hours each week walking, running, stair-stepping, etc., and are displeased with the results on the scale or in the mirror,” wrote Barry Braun, an associate professor of kinesiology at the University of Massachusetts at Amherst, in the American College of Sports Medicine’s February newsletter.

But a growing body of science suggests that exercise does have an important role in weight loss. That role, however, is different from what many people expect and probably wish. The newest science suggests that exercise alone will not make you thin, but it may determine whether you stay thin, if you can achieve that state. Until recently, the bodily mechanisms involved were mysterious. But scientists are slowly teasing out exercise’s impact on metabolism, appetite and body composition, though the consequences of exercise can vary. Women’s bodies, for instance, seem to react differently than men’s bodies to the metabolic effects of exercise. None of which is a reason to abandon exercise as a weight-loss tool. You just have to understand what exercise can and cannot do.

“In general, exercise by itself is pretty useless for weight loss,” says Eric Ravussin, a professor at the Pennington Biomedical Research Center in Baton Rouge, La., and an expert on weight loss. It’s especially useless because people often end up consuming more calories when they exercise. The mathematics of weight loss is, in fact, quite simple, involving only subtraction. “Take in fewer calories than you burn, put yourself in negative energy balance, lose weight,” says Braun, who has been studying exercise and weight loss for years. The deficit in calories can result from cutting back your food intake or from increasing your energy output — the amount of exercise you complete — or both. When researchers affiliated with the Pennington center had volunteers reduce their energy balance for a study last year by either cutting their calorie intakes by 25 percent or increasing their daily exercise by 12.5 percent and cutting their calories by 12.5 percent, everyone involved lost weight. They all lost about the same amount of weight too ­— about a pound a week. But in the exercising group, the dose of exercise required was nearly an hour a day of moderate-intensity activity, what the federal government currently recommends for weight loss but “a lot more than what many people would be able or willing to do,” Ravussin says.

At the same time, as many people have found after starting a new exercise regimen, working out can have a significant effect on appetite. The mechanisms that control appetite and energy balance in the human body are elegantly calibrated. “The body aims for homeostasis,” Braun says. It likes to remain at whatever weight it’s used to. So even small changes in energy balance can produce rapid changes in certain hormones associated with appetite, particularly acylated ghrelin, which is known to increase the desire for food, as well as insulin and leptin, hormones that affect how the body burns fuel.

The impact of exercise on the appetite and energy systems, however, are by no means consistent. In one study presented last year at the annual conference of the American College of Sports Medicine, when healthy young men ran for an hour and a half on a treadmill at a fairly high intensity, their blood concentrations of acylated ghrelin fell, and food held little appeal for the rest of that day. Exercise blunted their appetites. A study that Braun oversaw and that was published last year by The American Journal of Physiology had a slightly different outcome. In it, 18 overweight men and women walked on treadmills in multiple sessions while either eating enough that day to replace the calories burned during exercise or not. Afterward, the men displayed little or no changes in their energy-regulating hormones or their appetites, much as in the other study. But the women uniformly had increased blood concentrations of acylated ghrelin and decreased concentrations of insulin after the sessions in which they had eaten less than they had burned. Their bodies were directing them to replace the lost calories. In physiological terms, the results “are consistent with the paradigm that mechanisms to maintain body fat are more effective in women,” Braun and his colleagues wrote. In practical terms, the results are scientific proof that life is unfair. Female bodies, inspired almost certainly “by a biological need to maintain energy stores for reproduction,” Braun says, fight hard to hold on to every ounce of fat. Exercise for many women (and for some men) increases the desire to eat.

Thankfully there has lately been some more encouraging news about exercise and weight loss, including for women. In a study published late last month in The Journal of the American Medical Association, researchers from Harvard University looked at the weight-change histories of more than 34,000 participants in a women’s health study. The women began the study middle-aged (at an average of about 54 years) and were followed for 13 years. During that time, the women gained, on average, six pounds. Some packed on considerably more. But a small subset gained far less, coming close to maintaining the body size with which they started the study. Those were the women who reported exercising almost every day for an hour or so. The exercise involved was not strenuous. “It was the equivalent of brisk walking,” says I-Min Lee, a researcher at Harvard Medical School and Brigham and Women’s Hospital and the lead author of the study. But it was consistently engaged in over the years. “It wasn’t something the women started and stopped,” Lee says. “It was something they’d been doing for years.” The women who exercised also tended to have lower body weights to start with. All began the study with a body-mass index below 25, the high end of normal weight. “We didn’t look at this, but it’s probably safe to speculate that it’s easier and more pleasant to exercise if you’re not already heavy,” Lee says.

On the other hand, if you can somehow pry off the pounds, exercise may be the most important element in keeping the weight off. “When you look at the results in the National Weight Control Registry,” Braun says, “you see over and over that exercise is one constant among people who’ve maintained their weight loss.” About 90 percent of the people in the registry who have shed pounds and kept them at bay worked out, a result also seen in recent studies. In one representative experiment from last year, 97 healthy, slightly overweight women were put on an 800-calorie diet until they lost an average of about 27 pounds each. Some of the women were then assigned to a walking program, some were put on a weight-training regimen and others were assigned no exercise; all returned to their old eating habits. Those who stuck with either of the exercise programs regained less weight than those who didn’t exercise and, even more striking, did not regain weight around their middles. The women who didn’t exercise regained their weight and preferentially packed on these new pounds around their abdomens. It’s well known that abdominal fat is particularly unhealthful, contributing significantly to metabolic disruptions and heart disease.

Scientists are “not really sure yet” just how and why exercise is so important in maintaining weight loss in people, Braun says. But in animal experiments, exercise seems to remodel the metabolic pathways that determine how the body stores and utilizes food. For a study published last summer, scientists at the University of Colorado at Denver fattened a group of male rats. The animals already had an inbred propensity to gain weight and, thanks to a high-fat diet laid out for them, they fulfilled that genetic destiny. After 16 weeks of eating as much as they wanted and lolling around in their cages, all were rotund. The scientists then switched them to a calorie-controlled, low-fat diet. The animals shed weight, dropping an average of about 14 percent of their corpulence.

Afterward the animals were put on a weight-maintenance diet. At the same time, half of them were required to run on a treadmill for about 30 minutes most days. The other half remained sedentary. For eight weeks, the rats were kept at their lower weights in order to establish a new base-line weight.

Then the fun began. For the final eight weeks of the experiment, the rats were allowed to relapse, to eat as much food as they wanted. The rats that had not been running on the treadmill fell upon the food eagerly. Most regained the weight they lost and then some.

But the exercising rats metabolized calories differently. They tended to burn fat immediately after their meals, while the sedentary rats’ bodies preferentially burned carbohydrates and sent the fat off to be stored in fat cells. The running rats’ bodies, meanwhile, also produced signals suggesting that they were satiated and didn’t need more kibble. Although the treadmill exercisers regained some weight, their relapses were not as extreme. Exercise “re-established the homeostatic steady state between intake and expenditure to defend a lower body weight,” the study authors concluded. Running had remade the rats’ bodies so that they ate less.

Streaming through much of the science and advice about exercise and weight loss is a certain Puritan streak, a sense that exercise, to be effective in keeping you slim, must be of almost medicinal dosage — an hour a day, every day; plenty of brisk walking; frequent long runs on the treadmill. But the very latest science about exercise and weight loss has a gentler tone and a more achievable goal. “Emerging evidence suggests that ­unlike bouts of moderate-vigorous activity, low-intensity ambulation, standing, etc., may contribute to daily energy expenditure without triggering the caloric compensation effect,” Braun wrote in the American College of Sports Medicine newsletter.

In a completed but unpublished study conducted in his energy-metabolism lab, Braun and his colleagues had a group of volunteers spend an entire day sitting. If they needed to visit the bathroom or any other location, they spun over in a wheelchair. Meanwhile, in a second session, the same volunteers stood all day, “not doing anything in particular,” Braun says, “just standing.” The difference in energy expenditure was remarkable, representing “hundreds of calories,” Braun says, but with no increase among the upright in their blood levels of ghrelin or other appetite hormones. Standing, for both men and women, burned multiple calories but did not ignite hunger. One thing is going to become clear in the coming years, Braun says: if you want to lose weight, you don’t necessarily have to go for a long run. “Just get rid of your chair.”

Gretchen Reynolds writes the Phys Ed column for the magazine. She is writing a book about the frontiers of fitness.

Why do Low Carb Diets Work? The Mechanism Explained

Low-carb diets work.

That is pretty much a scientific fact at this point.

At least 23 high quality studies in humans have shown this to be true.

In many cases, a low-carb diet causes 2-3 times more weight loss as the standard low-fat diet that we’re still being told to follow (1, 2).

Low-carb diets also appear to have an outstanding safety profile. No serious side effects have been reported.

In fact, the studies show that these diets cause major improvements in many important risk factors (3).

Triglycerides go way down and HDL goes way up. Blood pressure and blood sugar levels also tend to decrease significantly (4, 5, 6, 7).

A high percentage of the fat lost on a low carb diet comes from the belly area and the liver. This is the dangerous visceral fat that builds up in and around the organs, driving inflammation and disease (8, 9, 10).

These diets are particularly effective for people with metabolic syndrome and/or type 2 diabetes. The evidence is overwhelming.

However, there is a lot of controversy about why these diets work.

People like to debate the mechanism, the stuff that is actually going on in our organs and cells that makes the weight go off.

Unfortunately, this is not fully known, and chances are that it is multifactorial – as in, there are many different reasons why these diets are so effective (11).

In this article, I take look at some of the most convincing explanations for the effectiveness of low carb diets.

Carb Restriction Lowers Insulin Levels

Insulin is a very important hormone in the body.

It is the main hormone that regulates blood sugar levels and energy storage.

One of the functions of insulin, is to tell fat cells to produce and store fat, and to hold on to the fat that they already carry.

It also tells other cells in the body to pick up glucose (blood sugar) from the bloodstream, and burn that instead of fat.

So, insulin stimulates lipogenesis (production of fat) and inhibits lipolysis (the burning of fat).

It is actually well established that low-carb diets lead to drastic and almost immediate reductions in insulin levels (12, 13).

Here is a graph from one study on low-carb diets (14).

Photo source: Diet Doctor.

According to many experts on low-carb diets, including Gary Taubes and the late Dr. Atkins, lower insulin levels are the main reason for the effectiveness of low-carb diets.

They have claimed that, when carbs are restricted and insulin levels go down, the fat isn’t “locked” away in the fat cells anymore, and becomes accessible for the body to use as energy, leading to reduced need for eating.

However, I’d like to point out that many respected obesity researchers do not believe this to be true, and do not think the carbohydrate-insulin hypothesis of obesity is supported by the evidence.

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Bottom Line: Blood levels of the hormone insulin go way down when carb intake is reduced. High insulin levels contribute to fat storage, and low insulin levels facilitate fat burning.

Water Weight Drops Rapidly in The Beginning

In the first 1-2 weeks of low carb eating, people tend to lose weight very quickly.

The main reason for this, is reduction in water weight.

The mechanism behind it is two-fold:

1. 1Insulin: When insulin goes down, the kidneys start shedding excess sodium from the body. This also lowers blood pressure (15).
   

2. 2Glycogen: The body stores carbs in the form of glycogen, which binds water in the muscles and liver. When carb intake goes down, glycogen levels in the body go down, and the water follows along.
   

This does not happen to nearly the same extent on a higher carb diet, even if calories are reduced significantly.

Even though some people use this as an argument against low-carb diets, reduced water weight should be considered an advantage.

I mean, who wants to carry around excess bloat and water weight all the time?

Anyway, despite claims to the contrary, this is far from being the main weight loss advantage of low-carb diets.

The studies clearly show that low-carb diets lead to more fat being lost as well, especially the “dangerous” belly fat found in the abdominal cavity (8, 16).

So, part of the weight loss advantage of low-carb diets is explained by reductions in water weight, but there is still a major fat loss advantage as well.

Bottom Line: When people go low-carb, they lose significant amounts of excess water from their bodies. This explains the rapid weight loss seen in the first week or two.

Low Carb Diets Are High in Protein

In most studies where low carb and low fat diets are compared, the low carb groups end up eating much more protein.

This is because people replace many low-protein foods (grains, sugars) with higher protein foods like meat, fish and eggs.

Numerous studies show that protein can reduce appetite, boost metabolism, and help increase muscle mass, which is metabolically active and burns calories around the clock (17, 18, 19, 20).

Many nutrition experts believe that the high protein content of low-carb diets is the main reason for their effectiveness.

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Bottom Line: Low carb diets tend to be much higher in protein than low fat diets. Protein can reduce appetite, boost metabolism and help people hold on to muscle mass despite restricting calories.

Low Carb Diets Have a Metabolic Advantage

Although this is controversial, many experts do believe that low carb diets have a metabolic advantage.

In other words, that low carb diets increase your energy expenditure, and that people lose more weight than can be explained by reduced calorie intake alone.

There are actually some studies to support this.

A study conducted in 2012 found that a very low carb diet increased energy expenditure compared to a low fat diet, during a period of weight maintenance (21).

The increase was around 250 calories, which is equivalent to an hour of moderate-intensity exercise per day!

However, another study has suggested that it may be the high protein (but not low carb) part of the diet that causes the increase in calories burned (22).

That being said, there are other mechanisms that may cause an additional metabolic advantage.

On a very low carb, ketogenic diet, when carb intake is kept extremely low, a lot of protein is being transformed into glucose in the beginning, a process called gluconeogenesis (23).

This is an inefficient process, and can lead to hundreds of calories being “wasted.” However, this is mostly temporary as ketones should start replacing some of that glucose as brain fuel within a few days (24).

Bottom Line: Low-carb diets appear to have a metabolic advantage, but most of it is caused by the increased protein intake. In the beginning of a very low carb, ketogenic diet, some calories are wasted when glucose is produced.

Low Carb Diets Are Less Varied, and Lower in “Food Reward”

Low carb diets automatically exclude some of the world’s most fattening junk foods.

This includes sugar, sugary drinks, fruit juices, pizzas, white bread, french fries, pastries and most unhealthy snacks.

There is also an obvious reduction in variety when you eliminate most high-carb foods, especially given that wheat, corn and sugar are in almost all processed foods.

It is well known that increased food variety can drive increased calorie intake (25).

Many of these foods are also highly rewarding, and the reward value of foods can impact how many calories we end up eating (26).

So, reduced food variety and reduced intake of highly rewarding junk foods should both contribute to a reduced calorie intake.

Bottom Line: Low carb diets exclude many foods that are highly rewarding and extremely fattening. These diets also have less food variety, which may lead to reduced calorie intake.

Low Carb Diets Significantly Lower Your Appetite, Leading to Automatic Reduction in Calorie Intake

Probably the single biggest explanation for the weight loss effects of low carb diets, is their powerful effects on appetite.

It is well established that when people go low carb, their appetite goes down and they start eating fewer calories automatically (27).

In fact, studies that compare low carb and low fat diets usually restrict calories in the low-fat groups, while the low-carb groups are allowed to eat until fullness (28).

Despite that, the low carb groups still usually lose more weight.

There are many possible explanations for this appetite reducing effect, some of which we have already covered.

The increased protein intake is a major factor, but there is also evidence that ketosis can have a powerful effect (29).

Many people who go on a ketogenic diet feel that they only need to eat 1 or 2 meals per day. They simply don’t get hungry more often.

There is also some evidence that low carb diets can have beneficial effects on appetite regulating hormones like leptin and ghrelin (30).

Bottom Line: Low carb diets lead to an automatic reduction in calorie intake, so that people eat fewer calories without having to think about it.

The Long Term Effects on Weight Loss Are Not Very Impressive

Even though low carb diets are very effective in the short-term, the long-term results are not that great.

Most studies that last for 1-2 years show that the difference between the low-carb and low-fat groups mostly disappears.

There are many possible explanations for this, but the most plausible one is that people tend to abandon the diet over time, and start gaining the weight back.

This is not specific to low carb diets, and is a well known problem in most long-term weight loss studies. Most “diets” are incredibly hard to stick to.

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Take Home Message

Some people refuse to accept that low carb diets can work, and that people can eat as much as they want, because that must violate the calories in, calories out model.

However, when you understand the mechanisms behind low carb diets, you can see that the CICO model is not being violated, and the laws of thermodynamics still hold.

The truth is, low carb diets work on both sides of the calorie equation.

They boost your metabolism (increasing calories out) and lower your appetite (reducing calories in), leading to automatic calorie restriction.

Calories still count, it’s just that low carb diets automate the process and help prevent the biggest side effect of conscious calorie restriction, which is hunger.

We all have been there. Gained a few pounds on that vacation, holiday season, struggled to lose that extra weight, and failed. A three pound gain turns into a 6 pound gain. Next month a few more pounds gain.  The average consumer is bombarded with misleading and false information. Most Physicians are only educated consumers, we struggle to make the most of the Science of weight loss. There has been increased scrutiny by the Research community into the false claims of many programs and there is no simple answer to a complex problem.

I have pirated info from a number of sites and papers in order to create a simplified explanation and  program on the basics of weight loss. A good resource is Wikipedia. Most of the information in Wikipedia is peer reviewed, and although it should not be considered gospel, it is a good place to start some basic research on a topic.