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The Role of Energy Expenditure in the Differential Weight Loss in Obese Women on Low-Fat and Low-Carbohydrate Diets

The following information is available at Pub Med and was not written by Atkins professionals.

The Journal of Clinical Endocrinology and Metabolism

Brehm, B.J., Spang, S.E., Lattin, B.L., et al., “The Role of Energy Expenditure in the Differential Weight Loss in Obese Women on Low-Fat and Low-Carbohydrate Diets,”Journal of Clinical Endocrinology & Metabolism, 90(3), 2005, pages 1475-1482.

Summary:

We have recently reported that obese women randomized to a low-carbohydrate diet lost more than twice as much weight as those following a low-fat diet over 6 months. The difference in weight loss was not explained by differences in energy intake because women on the two diets reported similar daily energy consumption. We hypothesized that chronic ingestion of a low-carbohydrate diet increases energy expenditure relative to a low-fat diet and that this accounts for the differential weight loss. To study this question, 50 healthy, moderately obese (body mass index, 33.2 +/- 0.28 kg/m(2)) women were randomized to 4 months of an ad libitum low-carbohydrate diet or an energy-restricted, low-fat diet. Resting energy expenditure (REE) was measured by indirect calorimetry at baseline, 2 months, and 4 months. Physical activity was estimated by pedometers. The thermic effect of food (TEF) in response to low-fat and low-carbohydrate breakfasts was assessed over 5 h in a subset of subjects. Forty women completed the trial. The low-carbohydrate group lost more weight (9.79 +/- 0.71 vs. 6.14 +/- 0.91 kg; P < 0.05) and more body fat (6.20 +/- 0.67 vs. 3.23 +/- 0.67 kg; P < 0.05) than the low-fat group. There were no differences in energy intake between the diet groups as reported on 3-d food records at the conclusion of the study (1422 +/- 73 vs. 1530 +/- 102 kcal; 5954 +/- 306 vs. 6406 +/- 427 kJ). Mean REE in the two groups was comparable at baseline, decreased with weight loss, and did not differ at 2 or 4 months. The low-fat meal caused a greater 5-h increase in TEF than did the low-carbohydrate meal (53 +/- 9 vs. 31 +/- 5 kcal; 222 +/- 38 vs. 130 +/- 21 kJ; P = 0.017). Estimates of physical activity were stable in the dieters during the study and did not differ between groups. These results confirm that short-term weight loss is greater in obese women on a low-carbohydrate diet than in those on a low-fat diet even when reported food intake is similar. The differential weight loss is not explained by differences in REE, TEF, or physical activity and likely reflects underreporting of food consumption by the low-fat dieters.

Commentary:

The following information was written by Atkins professionals.

Obese, healthy women were assigned to follow either a low carb or low fat diet for 4 months. The low carb group was instructed to limit carbohydrate intake to 20 grams a day for the first 2 weeks, and then increase their carbohydrate intake up to 60 grams as long as they remained in ketosis. Individuals in the low fat group were instructed to consume a diet that was 55% carbohydrate, 15% protein, and 30% fat. Both groups were given nutrition counseling and were instructed to record energy expenditure using a pedometer. Results indicated that women on the low carb diet lost significantly more weight, even though there was no difference in calorie intake or energy expenditure. This supports the metabolic advantage phenomenon in controlled carbohydrate nutrition.

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