A hormone released by muscles during exercise transforms white fat cells in the body into brown fat cells, reports the June 2012 Harvard Health Letter. The hormone, known as irisin, also appears to help prevent or overcome insulin resistance, a condition that leads to type 2 diabetes.
White fat cells simply store fat. Brown fat cells, in contrast, actually burn fat. And brown fat cells keep burning fat even after you've stopped exercising.
"Irisin travels throughout the body in the blood and alters fat cells," explains Dr. Anthony Komaroff, editor in chief of the Harvard Health Letter. "If your goal is to lose weight, you want to increase the number of brown fat cells and decrease white fat cells."
Babies are born with brown fat, but it was thought to gradually disappear. In 2009, several studies showed that adults still have brown fat cells. Earlier this year, a team led by Dr. Bruce Spiegelman, professor of cell biology and medicine at Harvard Medical School, identified how irisin transforms white fat cells into brown ones in mice, and found that humans have irisin, too. It is very likely, though not proven, that irisin has similar effects in humans as it does in mice.
"Studies like these are just plain interesting, in and of themselves," says Dr. Komaroff, who is also an internist and professor of medicine at Harvard Medical School. "They help us to better understand how our bodies work. However, the discovery of irisin also could have some very practical and beneficial applications. Theoretically, irisin could become a treatment to help us maintain a healthy body weight, and reduce the risk of diabetes."
Read the full-length article: "Major fat-burning discovery"
The June Harvard Health Letter also shines a light on how to protect yourself from too much sun this summer, with advice on which SPF sunscreen you need and how best to apply it to lower your risk of skin cancer.
Also in this issue:
- When sex is safe after a heart attack
- How sweet treats may keep you on your diet
- How special contact lenses deliver pain relief after eye surgery