Low-Carb Vs. Low-Fat—Which Diet Leads to Long-Term Weight Loss?
People on a low-carbohydrate diet experience greater improvements in blood sugar control and in some heart disease risk factors than people on a low-fat diet; however, although low-carb dieters may lose weight more quickly that low-fat dieters, long-term weight loss is not substantially different, according to two studies published in the Annals of Internal Medicine (2004;140:769–77, 778–85).
As the rate of obesity in the United States climbs to unprecedented levels, increasing numbers of people are searching for the ideal weight-loss diet. People in the United States spend $33 billion each year on weight-loss products and services, yet fewer than 25% of people trying to lose weight actually follow recommendations for reducing calorie intake and increasing exercise. For many years, most nutrition authorities have recommended a low-fat diet for weight loss and prevention of diseases linked to obesity, such as type 2 (adult onset) diabetes and heart disease.
Though there has been little information on the short- and long-term effects of low-carbohydrate diets on weight loss and overall health, the popularity of low-carbohydrate diets exploded in recent years. For example, in the last decade there has been a resurgence of interest in the Atkins Diet, a low-carbohydrate diet developed in the 1970s. Other low-carbohydrate diets that are loosely modeled on the Atkins Diet, such as the South Beach Diet, have also gained recent popularity.
In the first of the new studies, 120 obese people with high cholesterol, LDL (“bad”) cholesterol, or triglyceride levels were randomly assigned to either a low-fat diet group or a low-carbohydrate (Atkins) diet group for almost six months (24 weeks). Both groups met regularly to answer questionnaires and receive instructions and supportive guidance. In keeping with the Atkins diet protocol, the low-carbohydrate diet group was instructed to eat no more than 20 grams of carbohydrate per day initially and to take daily nutritional supplements including chromium (1,800 mcg); D,L-phenylalanine (900 mg); L-carnitine (3,000 mg); and a green tea extract (80 mg). The low-fat diet group was instructed to consume 30% or fewer of their daily calories from fat and 10% or fewer of their calories from saturated fats, and to keep cholesterol intake under 300 mg per day. The average weight loss at the end of the study was significantly greater in the low-carbohydrate group than in the low-fat group (28 pounds versus 15 pounds).
In the longer of the two studies, 132 obese people participated, 83% of who had type 2 diabetes. They were randomly assigned to either a low-fat group or low-carbohydrate group for one year. The instructions in the low-fat group were to get no more than 30% of daily calories from fat, while the low-carbohydrate group was advised to eat no more than 30 grams of carbohydrate per day. The low-carbohydrate group lost weight more quickly than the low-fat group—about 13 pounds versus about 4 pounds in the first six months. Between six months and one year, however, the low-fat group continued to lose weight while the low-carbohydrate group regained some of the lost weight. After one year, the low-carbohydrate group had still lost more weight than the low-fat group (11 versus 7 pounds), but the difference was no longer statistically significant.
Both studies noted a significantly greater drop in triglycerides in the low-carbohydrate group than in the low-fat group. The six-month study further noted an increase in levels of beneficial HDL cholesterol in the low-carbohydrate group, although the one-year study simply observed that the low-carbohydrate diet resulted in less of a drop. People with diabetes on the low-carbohydrate diet had slightly greater improvement in markers of blood sugar control after one year than diabetics on the low-fat diet, although this difference was not statistically significant.
The results of these studies suggest that a low-carbohydrate diet can induce more rapid weight loss than a low-fat diet, but long-term weight loss is only slightly better with the low-carbohydrate diet. Some of the nutritional supplements (such as chromium; L-carnitine; D,L-phenylalanine; and green tea extract) used in combination with the Atkins diet in the six-month study might reduce food cravings or directly promote weight loss. Additional research is needed to determine how much these supplements contributed to the weight loss observed in that study.
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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