HEALTH UPDATES

The Low-Fad Diet Approach:

A Solution to the Obesity Problem

Recent studies reveal how the right combination of macronutrients can facilitate weight loss

With more than two-thirds of U.S. adults classified as either overweight or obese, developing guidelines to help achieve and maintain a healthy body weight, is a key national health objective.

New research is helping to explain the causes and possible solutions for the near-epidemic weight gain in Americans over the last few decades. Notably, a study by Dansinger, et al, published last year in the Journal of the American Medical Association, showed that the amount of weight dieters lost after one year was modest, regardless of the diet selected (Atkins, Ornish, Weight Watchers or Zone). Importantly, the JAMA study showed a 42% drop out rate by study participants. A message from these studies is that the current crop of popular “fad” diets is not a practical long-term solution to the obesity problem.

Part of the solution to this growing health issue may lie in findings that were published in two other recent studies. In the first study, highlighted last July in the American Journal of Clinical Nutrition, researchers were interested to learn why low-carbohydrate diets help subjects to lose weight. What they found is that the macronutrient mixture, namely high-protein, not the low-carbohydrate content of popular diets like Atkins, helps people to lose weight. The reason appears to be that protein is more satiating and energy-burning than either carbohydrate or fat.

In the study, researchers varied the amount of protein and fat study participants consumed while keeping carbohydrate constant. During the initial two weeks, 19 healthy individuals were placed on a weight-maintaining 2,000-calorie diet that consisted of 15% (by energy) protein, 35% fat and 50% carbohydrate. For the next two weeks, also in a 2,000-calorie diet, protein was doubled to 30% while fat was reduced to 20% and carbohydrate remained the same at 50%. In the final 12 weeks of the study, participants did not have a caloric limit but had to maintain the high-protein diet. To monitor results, patients were asked how hungry they felt between and after meals. In addition, researchers measured levels of important satiety and hunger-related hormones including leptin and ghrelin. The study excluded individuals with a body mass index of 30 or higher; those who did aerobic exercise for more than 30 minutes three times a week; those who used tobacco, alcohol, or had diabetes or any other medical condition.

What the researchers found is that people became more satiated on the high-protein (30%) diet. During the second two weeks of the trial, patients reported feeling more satiated on the high-protein diet despite no significant change in leptin levels. Even during the 12 week phase when participants did not have any caloric restrictions, on average they consumed 450 fewer calories per day and lost about 11 pounds overall. The study results could not be explained by the hunger hormone ghrelin which increased or the satiety hormone leptin which decreased during this phase of the research.

A second study, by Howard, et al was published in the January 2006 issue of JAMA. The researchers wanted to test the hypothesis that a low-fat, high-carbohydrate diet – a diet which is promoted by organizations such as the American Cancer Society and American Heart Association - has contributed to the rise in obesity over the past several decades. Not surprisingly, this is a notion that has been purported by advocates of low-carb diets like Atkins and The South Beach Diet.

The low-fat study was part of the Women’s Health Initiative which followed about 48,000 postmenopausal women for an average of 7.5 years. About 40% of the women in the study were assigned to a low-fat diet with the remaining 60% of the women assigned to a control group. At baseline, both sets of women consumed at least 32% of their daily caloric intake from fat. Women in the low-fat group were told to consume no more than 20% of their daily caloric intake from fat. These women also participated in a series of group sessions designed to reduce dietary fat intake while increasing complex carbohydrate intake. The control group was not given any specific dietary restrictions but received a copy of the Dietary Guidelines for Americans. Neither group was instructed to exercise or to restrict their caloric intake.

During the first year of the study, women on the low-fat diet lost an average of 4.8 pounds compared to the control group. In addition, many of the women maintained their weight loss over the next several years. Based on these results, the researchers concluded that a low-fat diet may prevent the tendency for women to gain weight during their postmenopausal years. They also concluded that a low-fat diet paired with complex carbohydrates such as fruits, vegetables and whole grains has not been a contributing factor to the rising rate of obesity in this country.

For the majority of healthcare professionals who are involved in providing care to an increasingly obese patient population, these two studies provide direction for weight management in these patients. Based on these findings, encouraging patients to consume 30% of their calories from protein, 20% from fat and 50% from complex carbohydrates seems prudent. Guidance should be based on helping patients to make quality choices within each macronutrient group, with emphasis on lean sources of protein, unsaturated fats and complex carbohydrates from fruits and vegetables.

References:
-National Center for Health Statistics, 1999-2002 National Health and Nutrition Examination Survey (NHANES)
-Dansinger et al, “Comparison of the Atkins, Ornish, Weight Watchers, and Zone diets for weight loss and heart disease risk reduction,” JAMA 2005; 293:43-53.
-Howard et al, “Low-fat dietary pattern and weight change over 7 years,” JAMA 2006; 295:39-49.
-Weigle et al, “A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations,” Am J Clin Nutr 2005; 82:41-8.

 

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