Fat Fighting Is Part of the Apple's Peel

Eating unpeeled apples may keep extra pounds and obesity-related diseases at bay, a study in PLoS ONE suggests.

Ursolic acid is a natural compound found in the waxy coats on apples and other fruits and herbs. Previous research showed that ursolic acid increased the activity of a protein that stimulated muscle growth and glucose metabolism in mice.

Ursolic acid, found in apples' waxy coats, triggered an increase in high-energy brown fat, which is associated with reduced obesity, in mice in an Iowa study.

In this follow-up study, researchers in Iowa tested ursolic acid on mice with diet-induced obesity. For six weeks, one group of mice had unlimited access to a diet of high-fat food proven to cause obesity, glucose intolerance and fatty liver disease. Two other groups of mice had unlimited access to the same diet, but supplemented with either 0.14 grams or 0.27 grams of ursolic acid per 100 grams of food. For comparison, an apple contains 50 milligrams of ursolic acid, equivalent to about 6% of the lowest dose given to the mice.

Ursolic-acid mice developed more skeletal muscle but gained less weight than nonsupplemented mice, even though food intake was higher in ursolic-acid mice. Supplemented mice had greater strength and exercise capacity, and higher resting energy expenditure. Ursolic acid triggered an increase in high-energy brown fat associated with reduced obesity, though it isn't known how, researchers said. The results were the same for both ursolic-acid doses...