| Fad Diets and Weight Loss | |
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More than half of all American adults are overweight, and this trend of excess weight gain is increasing by the day. It is not surprising that interest in weight loss is also increasing, a fact that is reflected in a large array of books to help Americans solve this problem.
What are these diets? The Zone diet1, Sugar Busters2, Carbohydrate Addict's Lifespan Program3, Protein Power Life Plan4, and Dr. Atkin's New Diet Revolution.5 Common to all of these diet programs is recommendation for too much protein, and the claim that insulin converts carbohydrates into fat, a claim we will discuss later. A close look at each of these five diets suggests that they cause loss of weight because the dieter really eats fewer calories. The Zone diet by Barry Sears1 is very specific. Its recommendations are quite complicated in order to get 4096 carbohydrate, 30% fat, and 30% protein (expressed as percent of total calories) in the meal. For The Zone diet this 40-30-30 ratio is important. An estimation of calories in the recommended three meals and two snacks each day would suggest that the caloric intake is low, with women eating approximately 1,400 calories per day and men about 1,800. The reported weight loss must be related to a reduced caloric intake.
The diet by Heller and Heller, The Carbohydrate Addict's Lifespan Program,(3) is a diet composed of two meals of meat, fish, cheese, and eggs, with non-starchy vegetables such as asparagus, spinach, cabbage, cucumbers, and green beans being permitted. The third meal permits one-third of the meal to include starchy vegetables, bread and a dessert, and a salad in every meal. The description of the diet is so vague, and the precise variation of interpretation of the instructions by each dieter so great, that reasonably accurate calculation of caloric intake is not possible. The diets of Eades and Eades, The Protein Power Lifeplan(4) and Atkins, New-Diet Revolution5 are similar—very high in protein, and very low in carbohydrate content. There are no restrictions on how much protein one eats. Both prescribe a two-week intervention (introductory) period, during which the carbohydrate maximum is 30 grams per day for Eades and Eades diet4 and 20 grams per day for the Atkins' diet.5 Each of these highly restrictive diets causes ketosis, which reduces the appetite and contributes to weight loss. We will explain in detail later what ketosis does. After the weight loss, the maintenance program for both diets is still low in carbohydrate content, allowing a maximum of 90 grams of carbohydrate per day for each diet, which amounts to 18% of calories from carbohydrate for a 2,000 total calorie diet. This is still very low intake, when you realize that 55-60% carbohydrate is recommended for good health. All the fad diets considered here are high in protein content. The Zone is 30% of calories as protein1 which is at least twice what is normally recommended and needed by the body. The other diets as described do not allow an exact percent of calories to be calculated for protein intake. A weight-loss diet similar to the ketogenic diets(4),(5) mentioned above was used with obese adolescents by Willie, et al.6 This diet included 80-100 grams per day of protein and 25 grams per day each of carbohydrates and fat. This ketogenic diet was eaten for eight weeks. It was most significant that although this diet was followed for only a short time, calcium excretion increased, and total-body bone mineral content decreased. This would suggest that there are serious consequences from adopting the ketogenic fad diets as described previously.(4),(5) Many studies have demonstrated that loss of calcium in the urine increases with high protein intake. This is because more alkaline ions (such as calcium) are needed to neutralize the acidic sulfates and phosphates that are produced during the processing of the excess protein by the body. Thus the bone serves as a source of calcium to neutralize this acid. Feskanich and his team(7) have reported an epidemiology study (based on comparing different populations) on the relationship of protein consumption and bone fractures in women. This involved 85,900 women, 39-59 years of age, from the Nurse's Health Study population. Over the 12-year follow-up time period of this study, women who ate more than 95 grams of protein from all sources per day had a greater risk of forearm fractures. A similar increase in risk was observed for animal protein, but vegetable protein was not found to be associated with fracture risk. Thus the high animal protein intake required by the five fad diets discussed here is considered to place the dieter at increased risk of osteoporosis. Another problem: metabolism (body handling) of the high protein diet involves the production of excess amounts of nitrogen waste products from the digestion of unphysiological amounts of protein, that must be disposed of by the kidneys. This increased burden of waste disposal by the kidneys harms some people with compromised kidney function. Ketone Bodies As we mentioned above, the high-protein, very low-carbohydrate diet does lead to ketosis. Why is this? (See http://en.wikipedia.org/wiki/Ketosis for details.) Excess dietary fats are stored in the body as triglycerides. These, in turn, are released from storage as fatty acids upon demand by a process called "lipolysis" (breakdown of fat). The released fatty acids are oxidized through a complex series of chemical reactions called "beta-oxidation;" the final product of beta-oxidation is a compound called acetyl-CoA, which is converted into energy. This conversion requires another complex series of reactions called the tricarboxylic acid (TCA) cycle. Each body cell uses the TCA cycle in the final conversion of glucose (by carbohydrate metabolism) to make energy to run that cell. For the TCA cycle to be functional, carbohydrate must be in that cell, being metabolized. When carbohydrate intake is low, the TCA cycle functions poorly and the acetyl-CoA of the partially oxidized fatty acids is converted to ketone bodies (acetone, acetoacetic acid, and beta-hydroxybutyric acid). Then, the deficiency of sufficient carbohydrate metabolism leads to the excretion of the ketone bodies. This occurs when the carbohydrate intake decreases below about 20% of the total caloric intake.
To summarize: for fat to be metabolized, carbohydrate must be metabolized simultaneously. Otherwise ketone bodies are formed.* When normal diets are eaten, very few ketone bodies are produced, and their concentration in the blood is very low. Only in starvation, or if a person eats the very low carbohydrate diet, or has uncontrolled diabetes (in which sugar is not entering cells to fuel them, but is remaining in the blood), are the ketone body concentrations in the blood significant. High levels are definitely not desirable! Are Carbohydrates Fattening? The common message from the "fad diet doctors" is that carbohydrates are fattening. They ignore the fact that carbohydrates are the main energy source in the human diet. In fact, the oxidation of glucose to energy is priority, with the formation of fat occurring only when a person eats more than is needed to produce enough energy to fuel his daily activities. These biochemical observations are verified by recent human dietary studies (8),(9).
Hill et al.(11) have stated that "it is clear that consumption of a high-fat diet increases the likelihood of obesity and that the risk of obesity is low in individuals consuming low fat diets." Likewise, a review of epidemiological studies indicates that a high-fat diet promotes the development of obesity.(12),(13) In addition, Astrup(14) has reported that ecological, cross-sectional, and prospective longitudinal studies (research that is planned ahead of time and conducted for a long enough time to be reliable) show that obesity is directly associated with percentage of dietary fat eaten, and negatively with percentage of calories from carbohydrates.
Insulin, Villain or Friend? The "fad-diet doctors" appear to be obsessed with designing diets to keep blood insulin levels as low as possible. A high-meat, low-carbohydrate diet seems to be their goal in order to achieve this objective. Also, their goal seems to be to promote a fear of insulin resistance, and they claim that the high-carbohydrate, low-fat diets recommended by the Health Human Services can promote the high insulin levels that can produce insulin resistance. Space will not permit me to deal with this issue at this time. Although insulin resistance can be associated with obesity, this does not demand the extreme diets. We need good scientific data from the "diet doctors," rather than the fuzzy logic—arm chair philosophy—that is being propounded. Holt et al.(16) have determined the insulin demand generated by 240-Kcal portions (1,000 KJ—or Kilo joules, a common unit of energy measurement) of common foods (called insulin index). In this study, insulin response to white bread is taken to be 100%. All other foods are compared to white bread. High carbohydrate-containing foods compare to meat and fish as follows: oatmeal, granola, white and brown pasta, and rye bread have insulin scores of 40, 46, 40, and 56 respectively. Compare this data with insulin scores of foods with very low carbohydrate content: beef and fish with insulin scores of 51 and 59 respectively. We mention this data be-cause it does call into question much of the "diet doctors" logic.
In summary, I suggest that the fad diet approach to insulin responses to foods and the proposed dietary solutions are very simplistic and apparently in error. The scientifically recommended high-carbohydrate, low-fat diet composed of unrefined grains, fruits, vegetables, and legumes stands as a superior diet. If you don't have diabetes then don't worry about insulin! Safe Weight Loss Method If you need to lose weight, the strategy recommended by Rolls and Miller(17) is a good approach. Their recommendation is to consume a low-fat diet made up of low-energy density (low calories) foods such as fruits, vegetables, and other foods high in fiber and complex carbohydrates. For the vegetarian, this is simple. The only foods in the vegetarian pyramid to limit would be visible fat (margarine, dressings, and cooking oils or fats) and the high-fat-containing foods such as olives, avocados, nuts, and soybeans. The rest of the foods in the vegetarian diet are low in fat content. Fruits and vegetables are especially bulky, because of their water and fiber content, besides being low in fat content. Health and freedom from obesity are both achievable while on a balanced vegetarian diet with regular exercise and steady stress control. If you would like to subscribe to The Journal of Health and Healing or order back issues where many more health articles are available, call 706-820-1493, Ext. 407. REFERENCES:
(10).Food and Agriculture Organization/Agro-stat. Computerized Information Series No. 1. Food Balance Sheets. Rome: Food and Agriculture Organization, 1991. (11).Hill, J.O., Melanson, E.L., and Wyatt, H.T., J Nutr, 130(Suppl.):284S-288S, 2000. (12).Golay, A. and Bobbioni, E., Int J Obes Relat Metab Disord,Suppl. 3:S2-11, 1997. (13).Tatavanni, P.A. and Ravussin, E.,Ann NY Acad Sci, 819:37-43, 1997. (14).Astrup, A., Int J Obes Relat Metab Disord, Suppl 3:S32-S36, discussion S41-S42, 1993. (15).McArdle, W.D., Katch, F.I., and Katch, V.L., Exercise Physiology, 4th Ed., Williams & Wilkins, Baltimore, 1996, p. 621. (16).Holt, S.H.A., Brand-Miller, J.C., and Petocz, P., Am J Clin Nutr, 66:1264-1276, 1997. (17).Rolls, B.J. and Miller, D.L.J Am Coll Nutr, 16:535-543, 1997. |
James W. Blankenship, Ph.D., is Adjunct Professor of Nutrition, Loma Linda University, Loma Linda, California. This article originally appeared in The Journal of Health and Healing and is used with their permission.
Especially popular are the books of five New York Times best-selling authors. Unfortunately, these five authors have a common major problem—their diet recommendations are contrary to basic nutritional principles and therefore are being identified, understandably, as "fad diets."
The Sugar Busters diet (2): the authors, Steward and others, do not define their diet so that a caloric estimation can be made. Starchy vegetables such as potatoes, beets, and carrots, and corn, rice, and bread from refined flour are excluded, while meat and dairy products are used liberally. It is a high protein diet with limited carbohydrate intake. The quantity of food as measured on the dinner plate with no seconds or thirds (see page 130) does suggest a diet of reduced caloric intake.
The diet doctors indicate that in this process a person is losing calories. This is true! At very low carbohydrate intake, 74% of the energy normally derived from this conversion from fat is lost if the TCA cycle cannot function.
Since the "fad-diet doctors" claim the high carbohydrate intake is responsible for the high level of fatness for the American people, let us look at the carbohydrate intake for various population groups around the world (see table below). According to this concept, and if the fad-diet doctors are correct, people in the Oriental countries should be very fat and Americans should be skinny! Notice also that North Americans consume around 1,000 calories more of energy (calories) per day than do population groups that have a high-carbohydrate intake. It appears that calories, not carbohydrates, are to blame for the fattening of Americans!
