An apple a day may do a lot more than keep the doctor away. A University of Iowa study finds a compound in apple peels helps to build muscle and burn fat.

Dr. Chris Adams, an endocrinologist and senior author of the study, says a waxy substance in apple peels called ursolic acid has astounding properties.

Dr. Adams says, “We found that in mice, as predicted, it reduced the changes biochemically that occur with muscle atrophy and by doing that, it blocked muscle atrophy, or it reduced it.”

The findings suggest the compound may be useful in treating muscle wasting diseases and possibly metabolic disorders like diabetes.

“We found that it actually promoted the growth of muscle, so the mice got bigger muscles and actually got stronger,” Adams says. “We can measure mouse strength with a little machine called a grip strength meter.”

Based on the research using mice, he says more study is needed to determine if this chemical will be able to benefit humans.

“Ursolic acid increased muscle, increased muscle strength and very interestingly, it reduced fat, it reduced total body fat and reduced blood glucose and also plasma cholesterol and triglycerides,” Adams says. “It didn’t have any harmful effect on the kidneys or liver or anything like that which makes sense because it’s a natural compound that we actually eat.”

He says muscle wasting is very common in people who are sick and sedentary, adding, it’s a primary factor in why people end up in nursing homes.

The U-of-I study was published in the journal Cell Metabolism.