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The Futility of Low-Calorie Diets

Two weeks ago, we reviewed 14 Ways to Get Fatter. Most people aren’t looking to actually gain body fat, but it can sometimes be more powerful to see what you are doing to yourself and the impact it can have, rather than talk about the things you should do to reverse it. There’s another reason I wanted to get that article out, though. It was to help you understand there are more reasons people gain body fat than gluttony and sloth. Conventional wisdom today still suggests people get fat because they eat too much or they are lazy, but research does not support that point of view.

People do in fact gain weight because they store more energy than they burn, but the cause of the excess fat storage does not come down to just eating too much or exercising too little.

To gain an appreciation for the complexity of the calorie balance equation, and to also help you see how your diet and lifestyle choices impact your ability to keep off excess body fat, we’ll take a few more articles to break down this issue. My biggest objective is to help you see how you can influence your body’s ability to regulate fat storage, which should help you make better decisions about the foods you eat, lifestyle you live and exercise program you follow.

From Simple to Complex

Conventional thought about obesity is that the human body is a simple machine, and any time the calorie value of food consumed exceeds the calorie value of energy expended, the body gains fat. The formula looks like this:

Weight Gain = Calories Consumed > Calories Expended

Looking at the human body as being bound to the above formula means those who are overfat are either lazy because they don’t burn enough calories or have no self-control because they eat too much. Talk about a blow to the ego of those who carry too much body fat!

The human body is not that simple. Though it’s possible to gain weight by eating too much, it’s not likely the cause of the obesity rates we’re seeing.

Gary Taubes, in his best-selling books Good Calories, Bad Calories and Why We Get Fat, points us in another direction, and a growing number of experts are beginning to agree. When people become fatter, they do in fact store more energy as fat. But for these people, the focus should be on why they store the calories as fat so well and why they burn fat so poorly.

Your body is supposed to burn mostly fat, most of the time. Sugar, or carbohydrate, is only burned for fuel when blood sugar levels are high, when exercise intensity is high, or when the body cannot access fat stores. Fat, not carbohydrate, is your body’s primary source of fuel.

Throughout the day, the body burns a mix of fat and carbohydrate, with a very small amount of protein. Ideally, at rest people should burn fat. However, those with elevated blood sugar and insulin burn a higher percentage of sugar, or carbohydrates, even in a rested state. As food is consumed (especially carbohydrate-rich foods) or activity intensity increases, the percentage of energy from fat decreases and the percentage of energy from carbohydrate increases.

Metabolic testing allows for easy measurement of fat and carbohydrate utilization for individuals at rest and during exercise. In designing nutrition and exercise programs, we regularly measure resting metabolism (CaloriePoint) and exercise metabolism (CardioPoint) which show us at varying activity levels how well an individual burns fat or carbohydrate. By measuring oxygen input and carbon dioxide output, we’re able to determine what’s called Respiratory Quotient (RQ). From this data, we can determine the percentage of fat or carbohydrate an individual burns. RQ varies between 0.7 and 1.0, and the lower the RQ, the higher the percentage of fat an individual burns.


If you want your body to lose fat, it has to use fat!

If diet and lifestyle choices shift the body’s metabolism toward burning more glucose than fat, it won’t be able to access stored fat, even if an individual eats a low-calorie diet. Many people believe by eating less and exercising more, they’ll be assured of losing body fat. But it doesn’t work that way.

 A 1200-calorie, low-fat, high-carbohydrate diet is often recommended for women by those who believe weight loss is all about calorie-counting. Men are often recommended a more generous 1600–1800 calories for weight loss. If a woman averaged 2200 calories in energy expenditure each day, a 1200-calorie diet should create a 1000-calorie deficit. Under such a calorie deficit, the 1000 other calories would ideally come from stored body fat. If fat isn’t accessible, the body makes up the energy gap by:

  • Burning available blood glucose and stored glycogen
  • Breaking down muscle tissue and converting it to glucose
  • Increasing appetite to a point where it’s difficult to not eat more than the 1200 calories
  • Reducing metabolic rate to reduce energy expenditure

The supply of glucose is limited, and once glucose levels fall, protein from muscle must be converted to glucose which results in a loss of muscle. The most obvious sign someone depends on glucose over fat for energy is they become irritable or fatigued just a few hours after eating. Do you know someone like that? Rising and falling blood sugar is common even among those who are not counting calories, but who do eat an excessive amount of carbohydrates. But the feelings can be a lot worse while trying to restrict calories. On top of that, most people who want to lose weight aren’t looking to lose muscle; they’re looking to lose fat.

As another way to close the gap between the small amount of energy an individual consumes on a low-calorie diet and the energy he or she burns, the body can slow its metabolic rate. Thyroid hormone, the body’s major regulator of metabolic rate, can be reduced. The reduction in thyroid production can continue long after someone falls off their diet. This sets them up for a significant weight rebound.

Finally, those following a higher-carb, low-calorie diet often find themselves with a constant, gnawing hunger. Consumption of junk food is often a regular fantasy for those on low-calorie diets as the body is yearning for more food. Interestingly, this kind of hunger is not seen in those on very low carbohydrate diets, provided they consume enough fat. Even those who fast often find a total loss of hunger after a day or so without food. Yet, those who attempt to keep total calories low while still eating a higher percentage of carbohydrates often find hunger never goes away.

Does this mean all low-calorie diets come with these “side effects” of hunger, muscle tissue loss, irritability and reductions in metabolic rate? Not necessarily. It appears that the main reason for these side effects of higher-carbohydrate, low-calorie diets is that they do not provide enough energy to the body’s cells.

If fat cells are allowed to supply their fatty acids to the body for energy, it would mean the body would have an almost limitless supply of energy. When fat is not allowed to be burned, the energy supply is significantly limited.

The question, then, is what would prevent fat from leaving the fat cells and making this major source of energy useless? That’s the question we’ll tackle next week.

Share thoughts and comments below.

Written by Tom Nikkola - Director of Nutrition & Weight Management

 This article is not intended for the treatment or prevention of disease, nor as a substitute for medical treatment, nor as an alternative to medical advice. Use of recommendations in this and other articles is at the choice and risk of the reader.

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Reader Comments (5)

One thing that I've been saying for years has to do with the body's ability to slow its metabolic rate. People trying to lose weight sabotage their efforts by severely restricting their calories, only to suffer from chronic tiredness and being cold. The end result is that they end up weighing less, but still have the fat because the body is trying desperately to hold onto reserves. The body goes into conserve mode because it adjusts to the number of calories it can metabolize. The result is fat retention and muscle wasting. I call it 'flabby-skinny'.

May 26, 2012 | Unregistered CommenterPhillip M Zeuner

I found some great information in your blog. This blog is very useful and helpful to me. Thank you for sharing this information with us informative .. I love your blog……

May 27, 2012 | Unregistered Commenterweight loss clinic

I can testify to the validity of this article with regards to the complexity of the body to burn/store fat. I always wondered about certain diets such as the french one. In France for instance, the french eat a very high fat diet made up of cheeses, whole milk,and all kinds of meats as well as a daily intake of wine. They exercise little at the exception of walking and yet, France has one of the lowest number of obese people in he world. I would argue that their carbohydrate intake is just as high with all kind of breads(baguettes anyone?). This article gives insight into other possibilities to why some people get fat and some don't regardless of diet. I like it very much.

May 27, 2012 | Unregistered CommenterTarik

So - the article is very helpful and if I'm understanding it correctly. Eat high protein, less carbs?
I've been working out with purpose for almost 2 years....first 18 months with exersice alone, still eating carbs and drinking alcohol. Jan 2012 rolls around I've lost zero pounds or inches....switched to strict limit of carbs - only eating veggies and protein - NO fruit at all, no wine ever!....lost 6 pounds in first week. So far total weight loss 24 pounds. Weight loss came to a standstill when I went back to eating bread carbs and fruit several times a week for the last 3 weeks.
I never get to eat bread again? Never get to eat a banana or have a glass of wine?

any thoughts?

May 29, 2012 | Unregistered Commenterjustme

@justme: Everyone is different. Are you at your goal weight? If not, it doesn't make sense to eat those foods if you're losing body fat without them. Once you achieve your desired weight, you may be able to introduce small amounts of starchy foods without regaining weight, but then the question becomes, is it worth it? You asked about bread, a banana and wine, which are all quite different foods. As for bread, I'd recommend you read my interview with Dr. William Davis (search "Dr. Davis" in the search box above). Understanding how far today's wheat is from what it once was, it's hard to encourage anyone to eat it at all. A banana is usually two servings of fruit. We recommend people eat three servings of non-starchy vegetables for each serving of fruit they eat, so a banana can be okay if it's balanced out with six servings of vegetables. A glass of wine is quite different. A glass of red wine and dry white wine fit well in a reduced carb nutrition plan. If what you were doing was working, stick with it. You made great progress so far. Don't let low-quality foods get in the way of achieving your ideal body composition.

June 2, 2012 | Unregistered CommenterTom Nikkola

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