
Low-Fat Diets Don't Necessarily Reduce Calorie IntakeBy Judy McBride March
27, 1998The popular belief that dietary fat increases people's calorie intake lost
credibility in a study of identical twins who ate both high-fat and low-fat
diets. But the study also suggests that genes exert some control over a
person's preference for a high- or low- fat diet. Researchers at the USDA Human
Nutrition Research Center on Aging at Tufts in Boston designed the two diets
for equivalent palatability, fiber content and calories per ounce--factors that
may affect calorie intake. USDA's Agricultural
Research Service and the National Institutes
of Health funded the study. On average, the seven sets of male twins chose about the same number of
calories when served a diet containing 20 percent fat calories and a diet
containing 40 percent fat calories. Four sets of twins ate more calories from
the high-fat menu. The other three pairs preferred the low-fat diet. This
suggests fat is not the dominant factor influencing people's calorie intake, and
the amount of calories per ounce of food may be more important, supporting some
earlier, short-term studies. It also suggests that genes influence the tendency
to overeat certain diets. The men metabolized both diets with equal efficiency. Together, these
findings may help explain why the U.S. population has added weight, although fat
intake has dropped and low-fat and fat-free products have flooded the market. Many such products are calorically dense. Edward Saltzman led the study in
collaboration with Gerard Dallal and Susan Roberts. Roberts, who heads energy metabolism research at the Boston center, is
conducting a larger study involving 90 sets of identical twins. It is designed
to determine to what extent people's genes contribute to body fat and
overweight. Roberts is scheduled to appear on tomorrow night's broadcast of "The
Pulse," a new ABC television show on health and nutrition scheduled to air
at 10 p.m. E.S.T. Scientific contacts: Edward Saltzman and Susan Roberts, Energy
Metabolism Laboratory, Human Nutrition
Research Center on Aging at Tufts, Boston, Mass. 02111, Saltzman's phone
(617) 556-3245, Roberts' phone (617) 556-3237, fax (617) 556-3344,
[email protected],
[email protected]. U.S. Department of Agriculture | |