Breaking Bad Fat

Physical activity can convert some of our bodies’ bad “white” fat into good, calorie-burning “brown” fat.

White Fat

It’s well established that exercise improves the metabolic proficiency of muscles. Now groundbreaking new research reveals that physical activity can also convert some of our bodies’ bad “white” fat into good, calorie-burning “brown” fat.

“White fat, or white adipose tissue, is generally thought to be unhealthy — especially the fat around the middle section,” says Laurie Goodyear, PhD, head of the integrative physiology and metabolism section at Joslin Diabetes Center in Boston. “But brown fat, instead of storing energy, actually burns energy. It’s very metabolic, so it consumes a lot of calories.”

Goodyear and her team found dramatic changes to the fat tissue in study participants who exercised for 12 weeks. And the changes transcended color.

“There were thousands of genes in the fat that changed when [participants] exercised,” Goodyear points out.

In a subsequent study, the Joslin researchers transplanted subcutaneous brown fat from active mice into sedentary mice and saw similar benefits, including increased glucose tolerance and insulin sensitivity. “We were definitely surprised by the extent of the effects,” Goodyear says.

As co-researcher Kristin Stanford, PhD, says, “Our work provides greater motivation than ever to get out there and exercise.”


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