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Overweight? Cutting Body Fat Before Dietary Fat Is Better

BOSTON, Mass., March 6, 2000--Are you overweight--with a body mass index (BMI) between 25 and 30--and your blood lipids are higher than your doctor would like? Then you will probably benefit more from cutting those extra pounds, by eating fewer calories and increasing physical activity, than from cutting dietary fat. That’s the gist of findings in this month’s Agricultural Research magazine, published by the U.S. Department of Agriculture’s Agricultural Research Service.

Two different heart-healthy diets were less effective at improving the cholesterol profile of overweight men than of normal-weight men, said Jose Ordovas at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston. Ordovas collaborated on the study, which was done in Spain by researchers at the University of Cordoba Medical School.

ARS administrator Floyd Horn noted that there’s already good evidence that dietary changes don’t have much of an effect on the blood lipids of obese people, those who have a BMI over 30. “Dr. Ordovas and his Spanish colleagues wanted to see if this carried over to people who are overweight but not obese,” Horn said. “Apparently it does.”

Total cholesterol in the overweight men dropped less than half that of the lean men--7 versus 16 percent--after switching from a diet high in total fat and saturated fat to one recommended by the National Cholesterol Education Program (NCEP). Likewise, artery-damaging LDL cholesterol dropped 9 percent in the overweight group versus 21 percent in the lean group. The NCEP diet is low in fat--28 percent of total calories--with only 10 percent saturated fat.

A second heart-healthy diet also had less impact on total and LDL cholesterol in the overweight men. Although this diet was high in fat--38 percent of total calories--more than half of it was monounsaturated fat (22 percent), the predominant fat in olive or canola oils.

The researchers concluded: “It’s more important for overweight people to lose weight than change the fat composition of their diets.”

People are generally considered overweight if their BMI is between 25 and 30. That’s equivalent to a 6-foot person weighing between 185 and 220 pounds; a 5-foot, 8-inch person between 165 and 195 pounds; or a 5-foot, 4-inch person between 146 and 170 pounds.

However, individuals who are very muscular can have such a high BMI without being “overweight.” To calculate your BMI, multiply your weight in pounds by 700, then divide the total by your height in inches and divide that result by your height in inches once more. Or you can search for one of several BMI calculators on the Web. Indiana University supports one at:

http://www.iupui.edu/~psych/info/notes/bmi.html

While being overweight dampened the effect of dietary fat changes on cholesterol in the study volunteers, it had the opposite effect on their blood triglycerides. That’s a measure of how much fat is in circulation. After consuming the diet high in monounsaturated fat for four weeks, the overweight group had a much bigger drop in triglycerides than the lean men’s group: 26 percent versus 4 percent.

“Based on these findings, it appears that portly people should substitute olive or canola oil for saturated fat in their diet,” said Ordovas.

The Agricultural Research magazine article on this topic is online.

The Agricultural Research Service is the chief scientific arm of the U.S. Department of Agriculture.

Scientific contact: Jose M. Ordovas, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Mass., phone (617) 556-3102, fax (617) 556-3103, ordovas_li@hnrc.tufts.edu.