Compound in Apple Peels Reduces Obesity

A natural substance found in apple peel—ursolic acid—may help reduce obesity and its associated health problems by increasing the amount of muscle and brown fat, two tissues recognized for their calorie-burning properties, according to a new study published in the journal PLoS ONE.

University of Iowa researchers studied mice on a high-fat diet over a period of several weeks. Half of the animals also received ursolic acid in their high-fat food. Mice whose diet included ursolic acid actually ate more food than mice not getting the supplement, and there was no difference in activity between the two groups. Despite this, the ursolic acid-treated mice gained less weight and their blood sugar level remained near normal. Ursolic acid-treated mice also failed to develop obesity-related fatty liver disease, a common and currently untreatable condition that affects about one in five American adults.

The study further showed ursolic acid consumption increased skeletal muscle, increasing the animals’ strength and endurance, and also boosted the amount of brown fat. Because both muscle and brown fat burn calories, the researchers investigated energy expenditure in the mice and showed that ursolic acid-fed mice burned more calories than mice that didn't get the supplement.

"Since muscle is very good at burning calories, the increased muscle in ursolic acid-treated mice may be sufficient to explain how ursolic acid reduces obesity. However, we were surprised to find that ursolic acid also increased brown fat, a fantastic calorie burner. This increase in brown fat may also help protect against obesity," the researchers said. "Our study suggests that ursolic acid increases skeletal muscle and brown fat leading to increased calorie burning, which in turn protects against diet-induced obesity, pre-diabetes, and fatty liver disease."