Effects of isoenergetic, low-fat diets on energy metabolism in lean and obese women.

Whether changing from a high-fat diet to an isoenergetic, low-fat, high-complex-carbohydrate diet results in thermogenic benefits is controversial. Brief dietary interventions and failure to account for the potential influence of body-fat distribution on energy metabolism could have confounded the interpretation of previous studies. To address these issues, eight upper-body obese, seven lower-body obese, and eight non-obese premenopausal women underwent measurements of body composition, resting energy expenditure, overnight energy expenditure, and meal fat oxidation at the end of a weight-stabilizing, high-fat (42%) diet, and after 4 wk of an isoenergetic, low-fat (27%) diet. No change in body composition, resting energy expenditure, overnight energy expenditure, or meal fat oxidation occurred. We conclude that isoenergetic shifts from dietary fat to dietary carbohydrate within the generally recommended range have little or no effect on energy metabolism, and that body-fat distribution does not predict differences in energy expenditure.