Medical researchers in Boston say they've discovered a hormone that boosts the amount of energy a body burns, raising hopes of a new treatment for obesity and diabetes.
The Dana-Farber Cancer Institute team has dubbed the hormone, which is normally created during exercise, irisin.
"It's exciting to find a natural substance connected to exercise that has such clear therapeutic potential," says postdoctoral fellow Pontus Bostroöm.
Irisin appears to have a 'direct and powerful' effect on adipose, or fatty, tissue – the body's subcutaneous deposits of white fat.
When irisin was injected into mice, found the team, it switched on genes that convert white fat into 'good' brown fat - in just the same way as when it was produced naturally through exercise. This leads to excess calories being burned off at a faster rate.
Irisin was also shown to improve glucose tolerance in mice fed a high-fat diet.
If irisin can be used as a teratment for obesity, it will have to be used alongside, rather than instead of exercise, as it doesn't appear to make muscles stronger.
However, when it was injected into sedentary mice that were both obese and pre-diabetic, the mice controlled their blood sugar and insulin levels better, and lost a small amount of weight.
When given for longer periods, says the team, the weight loss could be greater.
Because irisin is a natural substance, and identical in mice and humans, the researchers say it should be possible to move very quickly to clinical testing – maybe within two years' time.