Nutrition Performance - Low-Carb Diets: The Truth… the Whole Truth

PEN: A New High-Carb/Low-Fat Mafia

The Partnership for Essential Nutrition (PEN) is purportedly dedicated to providing guidance regarding the important contribution all three macronutrients— carbohydrates, protein and fat— play in promoting good health and successful weight loss and to present the latest scientific evidence describing a healthful range for each. Although PEN´s core message (i.e., we should eat healthy carbs such as vegetables, fruits and whole grains) is certainly legitimate, they also provide common misinformation and pseudoscientific propaganda on low-carbohydrate/high-protein diets. Thus, I refute the misconceptions and propaganda and replace them with scientific facts.

Misconception # 1

“A review of studies on low-carbohydrate diets published in the May, 2004, issue of the American Journal of Clinical Nutrition found no advantage to these diets compared to equal calorie diets that include carbohydrates. Conducted by researchers at the University of Wisconsin at Madison, this review concluded that calories, not the composition of the diet, was responsible for weight loss and there are no differences in satiety (the feeling of fullness) between the two dietary approaches.”

In reality, the authors concluded that diets high in protein and/or low in carbohydrate produced greater weight loss (approximately equal to 2.5 kilograms, or 5.5 pounds) after 12 weeks of treatment. Thus, it appears the PEN people cannot read. Alternatively, they simply can’t handle the truth.

Misconception #2

“According to a scientific review published in the Journal of the American Medical Association, weight loss on low-carbohydrate diets is principally associated with decreased caloric intake.”

In the true low-carbohydrate group, the mean weight loss in trials was 17 kilograms (37.4 pounds), while in the higher-carbohydrate group it was only two kilograms (4.4 pounds). Oddly, the authors do not consider this significant. Only by intermingling trials of low-to-medium and high-carbohydrate diets could the authors reach the misleading conclusion quoted above.

Misconception #3

“What researchers have found is that temporary additional weight loss on low-carbohydrate diets is entirely explained by metabolic dehydration.”

Low-carbohydrate/high-protein diets indeed provide a “metabolic advantage,” a greater weight loss per calorie consumed compared to isocaloric, high-carbohydrate diets. The idea that metabolic advantage might violate laws of thermodynamics has some immediate appeal, but it’s not theoretically correct. (See the paper by Drs. Feinman and Fine published in Metabolic Syndrome and

Related Disorders; free full-text paper is available at www.liebertpub.com/MET/default1.asp).

Misconception #4

“An increasing body of research also suggests that what people eat when they go on very low-carbohydrate diets— proteins… may put their health at risk.”

Contrary to popular belief, supported by animal rights activists and vegetarian zealots, high-protein diets are, if anything, protective against heart disease. For example, Dr. J.G. Dumesnil and co-workers at the Quebec Heart Institute in Canada investigated the short-term (six days) nutritional and metabolic effects of an ad libitum (at one’s pleasure and not obligatory) low-glycemic index/low-fat/high-protein diet compared with the purportedly “heart healthy” American Heart Association (AHA) diet consumed ad libitum (British Journal of Nutrition, 2001;86:557-568).

During the ad libitum version of the AHA diet, subjects consumed 11,695 kilojoules per day (about 2,795 calories) and this diet induced a 28 percent increase in triacylglycerols (harmful blood lipids) and a 10 percent reduction in good cholesterol. In sharp contrast, the low-glycemic index/low-fat/high-protein diet consumed ad libitum resulted in a spontaneous 25 percent decrease in total energy intake, which averaged 8,815.0 kilojoules (about 2,107 calories) per day. Further, the low-glycemic index/low-fat/high-protein diet produced a substantial decrease (-35 percent) in triacylglycerols and marked decreases in plasma insulin levels measured either in the fasting state, over daytime and following a 75-gram oral glucose load. The authors concluded that a low-glycemic index/low-fat/high-protein diet may have unique beneficial effects compared with the AHA diet for the treatment of the atherogenic metabolic risk profile of abdominally obese patients. Translation: although this study was short-term intervention, these results strongly suggest that the “heart healthy” AHA diet may actually promote heart disease!

Further, a high-protein diet may actually protect against osteoporosis because proteins increase circulating insulin-like growth factor-I (IGF-1). IGF-1 is an essential factor for bone formation. Finally, there are no data in the scientific literature demonstrating that healthy kidneys and liver are damaged by the increased demands of protein consumed in quantities two to three times above the Recommended Dietary Allowance. (See my recent paper published in the Sports Nutrition Review Journal; free full-text paper available at www.sportsnutritionsociety.org).

Misconception #5

“Specifically, the IOM [Institute of Medicine] report states that… Adults should get 45 percent to 65 percent of their calories from carbohydrates, 20 percent to 35 percent from fat and 10 percent to 25 percent from protein.”

It’s becoming increasingly clear that PEN people cannot read. The Dietary Reference Intakes Report issued by the Institute of Medicine in 2002 stated that the Acceptable Macronutrient Distribution Range (AMDA) for protein is 10 to 35 percent of energy for adults. Hey… wait a minute… 10 to 35 percent? Do you guys recall what the AHA Nutrition Committee’s spokeswomen Barbara Howard said in 2001 about the Zone-diet and protein intake? Well, here is her comment:

“We continue to have reservations concerning The Zone diet as proposed in the publications by Dr. Sears and employed by many Americans. Our main concern centers on the consumption of protein. Although a woman of Ms. Chambers’ size might eat no more than 77 grams of protein, many larger individuals could easily consume more than 100 grams per day. In fact, the average protein requirement for a 70-kilogram man is only 56 grams per day. As we pointed out in our publication [an AHA statement on dietary protein and weight reduction], the human body is not able to store excess protein, and thus metabolic burden is placed on the liver and kidney in order to metabolize and to excrete the excess nitrogen.” Gee Barbara, I’m pretty sure that Nobel Prize committee is knocking on your door. Clearly, the AHA Nutrition Committee is lacking basic knowledge of nutritional physiology/biochemistry.

Misconception #6

“Studies have found that both in the form of starch and sugars, carbohydrates aid satiety, which leads people to eat less.”

Nonsense! Studies indicate that consumption of low glycemic carbohydrates (e.g., vegetables, legumes) may delay the return of hunger and reduce subsequent energy intake relative to consumption of higher glycemic carbohydrates (e.g., sugar, potatoes, rice) (Nutr Clin Care, 2003;6:20-26). Further, physiological studies demonstrate that consumption of high glycemic meals induce a sequence of hormonal changes that limit availability of metabolic fuels in the post-prandial (after eating) period and cause overeating (Asia Pac J Clin Nutr, 2003;12:S8.).

PEN Has a Hidden Agenda

OK, who the heck is behind the PEN? Well, PEN was founded by Barbara J. Moore. She is currently a President and Chief Executive Officer of Shape Up America!, a quasi-medical organization that claims to promote healthy weight and increased physical activity in America. Also, Moore served as general manager of program development and primary technical policy advisor for Weight Watchers International, the ultimate promoter of unhealthy very-high-carbohydrate, high glycemic diets. Indeed, Ms. Moore admitted that Weight Watchers sponsors PEN.

Oddly enough, Weight Watchers has now decided to add the first low-carbohydrate products to its range in the form of four frozen ready-made meals. This is so hypocritical and cheesy! They are launching low-carb products to cash in, while at the same time decrying low-carb itself! Conclusion: Weight Watchers will sell anything. There is certainly no scientific consistency regarding their nutritional beliefs because they are only interested in following the lucrative diet fads of the day and netting the contents of as many pocketbooks as they can. This, of course, means Weight Watchers´ long-term effectiveness amounts to nothing more than chance.

New Nutrition Journal

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