A new discovery in mice has researchers confident they can develop new medications to help combat mid-life obesity and ultimately decrease the rates of heart disease, diabetes and other illnesses.

A team of scientists led by the National Institutes of Health have pinpointed an enzyme in mice that could upend current theories as to why people gain weight as they age, and might lead to new effective weight-loss medications.

“Our society attributes the weight gain and lack of exercise at mid-life [approximately 30-60 years] primarily to poor lifestyle choices and lack of will power, but this study shows that there is a genetic program driven by an overactive enzyme that promotes weight gain and loss of exercise capacity at mid-life,” Dr. Jay Chung, Ph.D., the lead author of the study and the head of the Laboratory of Obesity and Aging Research at the National Heart, Lung and Blood Institute (NHLBI), said in a statement.

The enzyme—called DNA-dependent protein kinase (DNA-PK)—increases in activity with age and promotes the conversion of nutrients to fat and decreases the number of mitochondria, tiny organelles in the cells that turn fat into energy to fuel the body.

The average adult in the U.S. gains 30 pounds between the age of 20 and 50, despite the fact that food intake generally decreases during this period. Mitochondria is also found in abundance among young people but decreases as people age.

By reducing DNA-PK activity the research team believes fat accumulation will decrease and the mitochondria number will increase.

During the experiment they administered an inhibitor that blocked the enzyme in one group that were fed high-fat foods, while withholding it in another group and found a 40 percent decrease in weight gain in the group that received the inhibitor. The inhibitor also boosted mitochondrial content in skeletal muscle and increased aerobic fitness in obese and middle aged mice while reducing the incidence of obesity and type-2 diabetes.

“Our studies indicate that DNA-PK is one of the drivers of the metabolic and fitness decline that occurs during aging, which makes staying lean and physically fit difficult and increases susceptibility to metabolic diseases like diabetes,” Chung said. “The identification of this new mechanism is very important for improving public health.

“The study opens the door to the development of a new type of weight-loss medication that could work by inhibiting DNA-PK activity,” he added