The Skinny on Fat: A Skeptical Evaluation of the Atkins and Other Low Carb Diets

Editor's note. As we went to press with this issue the controversy over the death of Dr Atkins erupted upon the unauthorized release of documents indicating that he may have died not just of complication of a head injury from a fall, but from being overweight. To date this has not been confirmed, but the cultural conversation surrounding the charge, has reintroduced a new level of doubt about the Atkins diet from nutrition experts. As always, we must turn to the science to answer the fundamental questions about all such low-carb diets. Patrick Johnson does so admirably within these page.

SINCE 1980, THE PERCENTAGE OF THE ADULT population in the U.S. that is obese has risen approximately 8 to 12%, and the prevalence of disease that is often associated with excessive body weight has increased correspondingly. In 1999, Americans spent about $60 billion on products that claim to aid in weight control. Some of the most popular products are diet plans with novel food restrictions. But scientific theory states that if an individual simply takes in more energy than he or she expends, the excess will be stored as fat. (1)

In the late 1990s the idea that obesity is caused by carbohydrates (sugars and starches) rather than overeating became popular and has been put forth in several diet books, such as Dr. Atkins' New Diet Revolution, Protein Power, Enter the Zone, Sugarbusters, and Neanderthin. (2) The specifies of these plans vary, but they all share the common claim that significantly reducing carbohydrates will lead to improved health and a reduction in body fat without an overall reduction in caloric intake. This, according to the authors, is due to the effect that reducing carbohydrates has on insulin levels and the subsequent availability of fat for use as an energy source.

After review of the basics of fat and carbohydrate metabolism, as well as the evidence for the efficacy of some of the common claims made by the respective authors, it becomes clear that, though theoretically plausible, these claims are not well supported. It is also apparent that the methods used by the authors to verify these claims are not scientific. At its simplest, weight loss still appears to involve the difficult task of increasing daily energy expenditure and lowering food intake. The authors who claim otherwise bear the burden of proof and, thus far, have not met that burden. (3)

An Introduction to Diet Science

In the body, carbohydrate breakdown occurs in what is known as the glycolytic pathway. The process, which is known as glycolysis, takes one sugar molecule and splits it into two pyruvate molecules (Figure 1). Pyruvate is further broken down in either an aerobic or an anaerobic fashion.

During aerobic metabolism (slow glycolysis), pyruvate is converted to a molecule called acetyl-coenzyme-A (acetyl-CoA), which then continues on to what is called the tricarboxylic acid (TCA) cycle. In anaerobic metabolism (fast glycolysis) acetyl-CoA is converted to lactate and does not go directly through TCA. (4)

Glycolysis, both fast and slow, is what allows mammals to perform high-intensity activity; when it is operating fat metabolism is slowed. If glycolysis is inhibited-- carbohydrate deprivation or metabolic dysfunction--fat metabolism becomes the prime source of energy, and the intensity level during activity becomes difficult to maintain at higher than about 50-60% of an individual's V[O.sub.2]max (aerobic capacity determined as a function of the volume of [O.sub.2] that one can consume in a given time period), an important physiological consideration for anyone who is trying to include regular moderate exercise in his or her lifestyle.

TCA and Oxidative Phosphorylatlon

The tricarboxylic acid (TCA) cycle, along with oxidative phosphorylation in the electron transport chain (ETC), is the body's primary means of adenosine triphosphate (ATP) generation. …

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The Ups and Downs of Weight Loss without Wellness

The Ups and Downs of Weight Loss without Wellness

If you are reading my articles, you probably have been on at least two kinds of diets in your life. Chances are you have been on a lot more than two. Perhaps you are one of the 16 percent of all women who are continually on a diet. That is the category I was in. I used to tell people that I had been on a diet since age twelve. 

Well, you and I are not alone. According to a government study in 1986, 32 million adult Americans are overweight and almost 16 million are severely overweight. Being overweight can often make you feel desperate about your life, and this desperate feeling encourages you to "try anything." A "try anything" attitude is what draws people to all of the various diets that are on the latest best-seller list at the bookstore. Unfortunately these diets, as you already know, do not work. 

Statistics demonstrate that of the millions of people who go on diets every year and lose weight, only 3 percent keep the weight off. The other 97 percent lose the weight and then, bingo, put it right back on. Talk about desperation! 

What is it about diets that keeps them from working? What makes the Wellness diet different from all the other diets out there? Well, simply put, this diet takes work whereas almost all the other diets promise something for nothing. Like almost everything else in life, if it is "something for nothing" it must be too good to be true. In the area of dieting, something for nothing is too good to be true.

WHY THE OTHER DIETS DO NOT WORK

One of the biggest reasons that other diets do not work is that they do not change the Fat Stat of your body. In fact, it is the Fat Stat which sabotages the diet. Here is how that sabotage happens. 

Let us say you go on a diet that allows only 500 calories a day, and those calories can be obtained from any kind of food. Your body says "Whoa, what's going on?" and tries to stop you from losing weight by activating your Fat Stat. While you are on a restricted diet, your Fat Stat is trying to preserve your weight and not allowing it to go down. This causes your metabolic rate, the rate at which your body burns calories, to go down. If it goes down, then your body will need fewer calories to maintain weight. So it follows that if your body needs fewer calories to maintain weight, then even though you have restricted your calorie intake your body will actually need fewer calories. In other words you will not lose weight. Having slowed down your eating habits, your body slows down too. Imagine your body in slow motion. To hold onto its weight, your body's metabolism slows down to use fewer calories. If you were stranded on a desert island without food this might help preserve your health, but barring that situation, you are out of luck. 

Of course, if you really restrict your caloric intake (with starvation, for example ), or if you go on a limited calorie diet for a period of two or three weeks, you will lose weight. This will happen because your Fat Stat can maintain your weight for only a limited amount of time. If you continually consume fewer calories than your body expends, you will lose weight. But then what happens when you start to eat normally again? Your Fat Stat goes wild with excitement when it sees all that food. It tries to return your body to its previous weight and to retrieve all the weight you lost. lt soaks up the extra calories (extra because you bad been consuming so few) and zaps the weight back on. 

The Fat Stat asked your body to conserve energy while you were dieting, so when you eat normally your body takes a while to adjust. During this adjustment period the body gains weight very rapidly because the Fat Stat is still busy conserving energy. Therefore, the normal caloric intake of 1500 will seem like 2000 or 2500 to your body and it will store those "extra" calories as fat. Remember, we evolved in a struggle for survival of the fittest. The fittest human being would be one who could survive during periods of drought and other natural disasters when food was unavailable. Therefore, the slowing down of metabolism for preservation of body weight was helpful in evolution and a positive attribute. However, it is not a positive attribute when you are trying to lose weight. Consequently, while it might have taken you a month to lose 5 pounds, it may take you only two weeks to gain the 5 pounds right back. Not only will you gain the 5 pounds back, but often, you will gain an extra pound or two as well. 

As your Fat Stat is subjected over and over again to calorie restrictive weight loss diets, such as starvation or very low calorie diets, it works harder to maintain your weight. So the more diets you have been on, the harder the Fat Stat fights against you. The more the Fat Stat fights back, the harder it is to lose weight and the easier it is to gain that lost weight back, plus a few extra pounds along the way. 

Way to Weight Loss

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