Fad Diets Put to the Test

By Jeremy Appleton, ND

Healthnotes Newswire (January 11, 2001)?Half of the American population is overweight or obese,^{1 2} and surveys show that most Americans are trying to lose or maintain weight.³ But do fad diets work? That depends on the definition of ?work.?

The United States Department of Agriculture (USDA) is in the process of evaluating the existing scientific evidence with regard to weight loss diets. The agency solicited public comment today in a meeting held at its offices in Washington, D.C. This input will be used for the final research design to be coordinated and implemented by USDA and its Human Nutrition Research Centers.

Preliminary results⁴ of the USDA?s research on weight loss diets may surprise some consumers?it found that all popular diets, as well as diets recommended by governmental and non-governmental organizations, result in weight loss. The relative composition of macronutrients (i.e., proteins, carbohydrates, and fats) is unimportant. Total calorie intake is the key. In the absence of physical activity, the agency reports, a diet containing 1,400 to 1,500 calories per day will result in weight loss in adults.

Of course, there is a catch. Weight loss is not the same as weight maintenance. The USDA is quick to point out that the currently popular high-fat, low-carbohydrate diets (e.g., Dr. Atkins? New Diet Revolution,⁵ Protein Power,⁶ Life Without Bread⁷) may produce rapid weight loss, but they do not teach people how to eat healthful, balanced diets. In other words, they do not teach people how to keep the weight off. When these diets end, the weight is regained.⁸ The USDA also criticized such diets on the grounds that they promote greater loss of body water than body fat.⁹ High-fat, low-carbohydrate diets are nutritionally inadequate. They are low in vitamin E, vitamin A, B vitamins, certain minerals, and dietary fiber. They are also high in saturated fat and cholesterol, which may elevate the risk of cardiovascular disease.

According to the USDA, successful long-term weight loss is defined as a 5% reduction in initial body weight that is maintained for at least one year. However, most people trying to lose weight have much greater expectations for weight loss programs, often to the point of being unrealistic. Among obese women, one researcher reported that their goals and expectations were for an average 32% reduction in initial body weight,¹⁰ an expectation that is unlikely to be realized even with the best available treatments.

USDA research found that diets restricting fats (e.g., Dr. Dean Ornish?s Program for Reducing Heart Disease¹¹ and the New Pritikin Program¹²) are the best bet for healthful weight loss and weight maintenance. These diets also provide other health benefits, such as lower cholesterol, improved control of blood sugar, and reduced risk of cardiovascular disease. The agency also found, contrary to popular belief, that fat-restricted diets do not make people feel hungrier; instead, they often increase the sense of fullness.^{13 14} This is because, like the low-carbohydrate diets, most fat-restricted diets are designed to allow people to eat as much of the permitted foods as they desire.

How well people maintain their body weight after a weight loss regimen is determined by many factors, including psychological issues, hormone levels, physical activity, and others. The USDA emphasized that controlled clinical trials of high-fat, low-carbohydrate and low- and very-low-fat diets are needed to answer questions regarding their long-term effectiveness (i.e., weight maintenance as opposed to weight loss) and potential long-term health benefits and/or risks.

This study is a reminder that rather than another diet book, millions of overweight Americans need scientifically validated, easily understood information on how to prevent putting on weight in the first place, and how to maintain an appropriate body weight once the excess pounds have been shed.

References:

1. Flegal KM, Carroll MD, Kuczmarski RJ, Johnson CL. Overweight and obesity in the United States: prevalence and trends, 1960?1994. Int J Obes Relat Metab Disord 1998;22:39?47.
2. Mokdad AH, Serdula MK, Dietz WH, et al. The spread of the obesity epidemic in the United States, 1991?1998. JAMA 1999;282:1519?22.
3. Serdula MK, Mokdad AH, Williamson DF, et al. Prevalence of attempting weight loss and strategies for controlling weight. JAMA 1999;282:1353?8.
4. USDA Coordinated Nutrition Research Program on Health and Nutrition Effects of Popular Weight-loss Diets. http://www.usda.gov (accessed January 10, 2001).
5. Atkins RC. Dr. Atkins? New Diet Revolution. New York: Avon Books, Inc., 1992.
6. Eades MR, Eades MD. Protein Power. New York: Bantam Books, 1996.
7. Lutz W, Allan CB. Life Without Bread. Los Angeles: Keats Publishing, 2000.
8. Yang MU, Van Itallie TB. Composition of weight lost during short-term weight reduction. Metabolic responses of obese subjects to starvation and low-calorie ketogenic and nonketogenic diets. J Clin Invest 1976;58:722?30.
9. Keckwick A, Pawan GL. Metabolic study in human obesity with isocaloric diets high in fat, protein or carbohydrate. Metabolism 1957;6:447?60.
10. Foster GD, Wadden TA, Vogt RA, Brewer G. What is reasonable weight loss? Patients? expectations and evaluations of obesity treatment outcomes. J Consul Clin Psychol 1997;65:79?85.
11. Ornish D. Dr. Dean Ornish?s Program for Reducing Heart Disease. New York: Ballentine Books, 1990.
12. Pritikin R. The New Pritikin Program. New York: Simon & Schuster, Inc., 1990.
13. Schaefer EJ, Lichtenstein AH, Lamon-Fava S, et al. Body weight and low-density lipoprotein cholesterol changes after consumption of a low-fat ad libitum diet. JAMA 1995;274:1450?5.
14. Siggaard R, Raben A, Astrup A. Weight loss during 12 week's ad libitum carbohydrate-rich diet in overweight and normal-weight subjects at a Danish work site. Obes Res 1996;4:347?56.

Jeremy Appleton, ND, is a licensed naturopathic physician, writer, and educator in the field of evidence-based complementary and alternative medicine. Dr. Appleton is Chair of Nutrition at the National College of Naturopathic Medicine and Senior Science Editor at Healthnotes.

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