During trials on mice they discovered that, by administering drugs to blocked the enzyme, the rodents lost almost half their excess body weight compared to a control group.
The study, the first to link the increased activity of this enzyme to ageing and obesity, appears in the current issue of Cell Metabolism.
They say they believe it could have ramifications for several chronic, obesity-related illnesses such as heart disease, diabetes, and other diseases that tend to increase with age, including cancer and Alzheimer's.
Researchers have known for years that losing weight and maintaining the capacity to exercise tends to get harder beginning between ages 30 to 40; the start of mid-life.
Dr Chung and his associates searched for biochemical changes that occurred in middle-aged animals, and found that an enzyme called DNA-dependent protein kinase, or DNA-PK, increases in activity with age.
Further work showed that DNA-PK promotes conversion of nutrients to fat, causing weight gain, and decreases the number of mitochondria, tiny organelles in the cells that turn fat into energy to fuel the body.
Mitochondria can be found in abundance among young people, but the numbers drop considerably in older people.
Dr Chung theorised that reducing DNA-PK activity may decrease fat accumulation and increase mitochondria number as well as promote fat burning, and by blocking the enzyme from working was able to prove his theory.
He added: "Our studies indicate that DNA-PK is one of the drivers of the metabolic and fitness decline that occurs during ageing, which makes staying lean and physically fit difficult and increases susceptibility to metabolic diseases like diabetes."
"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."
