Impact Your Health and Metabolism with Food
By Maureen Williams, ND
Healthnotes Newswire (March 31, 2005)—A low-calorie diet that emphasizes foods with a low glycemic load (a measure of a food’s effect on blood glucose levels relative to white bread) is less likely to slow metabolic rate and decreases cardiac risk more than a low-calorie, low-fat diet, according to the Journal of the American Medical Association (2004;292:2482–90).
Among the many challenges of dieting is that eating fewer calories causes the body to use less energy, even when at rest. As the resting metabolic rate (also called resting energy expenditure) declines, dieting people also experience a real increase in hunger, which makes it more difficult to resist eating. The combination of lower energy expenditure and giving in to increased hunger may result in a slowing or halting of weight loss. This observed inclination for the body to resist weight loss has led to speculation that the body has a preferred weight, or a weight set-point, that is difficult to overcome. The body weight set-point is believed to be influenced not only by genetics but also by behavioral and environmental factors, which account for the general upward trend in body weight in the United States over the past several decades.
It has been suggested that the composition of the diet, rather than simply its calorie content, might have an important effect on the body’s resistance to weight loss. Several preliminary studies have found that a diet composed of foods that do not cause a rapid or dramatic rise in blood glucose levels (a low-glycemic-load diet) is less likely to trigger the body’s mechanisms for resisting weight loss than diets with a high-glycemic load.
In the current study, 46 overweight people who were otherwise healthy were randomly assigned to eat either a low-fat, low-calorie diet or a low-glycemic-load, low-calorie diet until they lost of 10% of their body weight. They were provided with standardized foods for three meals and one snack each day and instructed not to eat other foods nor change their activity level during the study.
The low-fat diet was consistent with the National Cholesterol Education Program guidelines for a heart-healthy diet. It included foods such as instant oatmeal, graham crackers, corn, dried fruit, and fruit juice. By contrast, the low-glycemic-load diet included foods with a low-glycemic load, such as oats, nuts, legumes, and fresh fruit.
Participants were weighed daily and asked questions about their hunger level. Resting energy expenditure was measured and blood tests were performed for each participant before beginning the diet and after reaching the goal of 10% weight loss (between nine and ten weeks on average). Weight loss was slightly faster for people eating the low-glycemic-load diet than for those eating the low-fat diet, but this difference was not statistically significant. People eating the low-glycemic-load diet experienced a 5.9% decrease in resting energy expenditure, while people eating the low-fat diet experienced a 10.6% decrease. Furthermore, the low-glycemic-load group reported lower hunger levels than the low-fat group. Blood tests revealed that insulin resistance and triglyceride levels decreased significantly more after weight loss in the low-glycemic-load group than the low-fat group. The level of C-reactive protein, a marker of inflammation that is linked to risk of heart disease, improved, dropping 50% in those eating the low-glycemic-load diet, while no change was observed in those eating the low-fat diet.
The results of this study demonstrate that weight loss achieved by eating a low-glycemic-load diet causes less of a drop in resting energy expenditure and less hunger than weight loss achieved through a low-fat diet. This suggests that weight loss should be easier to maintain over time with a low-glycemic-load diet. Further research is needed to determine whether the benefits of a low-glycemic-load diet persist for longer periods of time. Findings from this study also add to the evidence that a low-glycemic-load diet is more protective of heart health than a low-fat diet.
Maureen Williams, ND, received her bachelor’s degree from the University of Pennsylvania and her Doctorate of Naturopathic Medicine from Bastyr University in Seattle, WA. She has a private practice in Quechee, VT, and does extensive work with traditional herbal medicine in Guatemala and Honduras. Dr. Williams is a regular contributor to Healthnotes Newswire.
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