Combining moderate exercise with leptin hormone, once heralded as a promising obesity treatment, can renew the hormone's ability to prevent weight gain, says a new study.
The study led by University of Florida researchers on rats showed that pairing leptin and a modest dose of wheel running prevented obese rats on a belt-busting, high-fat diet from putting on weight.
"They don't run enough to use sufficient energy to prevent weight gain," said Dr Philip Scarpace, Ph.D., a professor of pharmacology and therapeutics in the UF College of Medicine and the senior author of the study.
"What the act of running appears to do is allow the leptin to work again. It's a demonstration that this simple act can reverse leptin resistance.
"Obese animals and humans don't respond to leptin at all. Our lab is interested in elucidating why this is the case. We know that often single-entity treatments are not successful. The concept was maybe a dual-entity treatment would work," he added.
Scientists believe that the low level of running triggered a metabolic change in the rats that cleared the way for the leptin signal to get through.
For the study obese rats were separated into three groups to test three approaches.
One group received leptin, another group got an exercise wheel and the third group got both leptin and a wheel.
In the normal-weight rats, leptin and exercise both worked to prevent weight gain. The normal-weight rats ran significantly more than their bulkier peers, logging in about two and a half miles a day on their wheels, and kept off weight proportionally to how much they ran. The rats were allowed to run as much as they chose.
The study also discovered that rats, which ran six to eight times less, neither running nor leptin alone kept the weight from accumulating. Giving the rats leptin actually caused them to gain more weight than eating a high-fat diet alone,
" This is a startling finding. Leptin is expected to reduce body weight, not promote weight and fat gain," said Scarpace.
He added that obese rats that ran and took leptin kept the extra weight off.
Christopher Morrison, Ph.D., an assistant professor at the Pennington Biomedical Research Centre at Louisiana State University said that the finding has potential to help combat obesity in humans.
However, scientists also believe that further studies are needed to understand exactly why this combination works.
The study appears in journal Diabetes.