Isoleucine is a branched-chain amino acid that might promote fat loss and improve metabolic health. Junko Nishimura and colleagues from Oita University in Japan, in a study on genetically obese mice, found that supplementing the diet with isoleucine for four weeks decreased blood triglycerides (blood fat) and increased the activity of PPAR-alpha and uncoupling proteins.

PPAR-alpha regulates fat cell growth and the action of insulin, while uncoupling proteins (UCPs) speed metabolic rate (calorie burning). Physical inactivity, poor diet, obesity, and genetics can slow the activity of PPARs and UCPs, causing obesity and insulin resistance. Supplementing isoleucine might help reduce body fat and improve metabolic health. (Journal Nutrition, 140: 496-500, 2010)