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    Molecule may hold clue to how exercise benefits body

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    Everyone knows exercise is good for you: It is a good way to prevent practically all diseases that come with age, stave off weight gain, and even relieve anxiety. But how does it work?

    For years, researchers have been slowly untangling exercise at the cellular level — if they can figure that out, they think it might be possible to emulate the beneficial effects of a workout with a pill. Now, a team led by researchers at Massachusetts General Hospital has identified a molecule that might be responsible for some of exercise’s beneficial effects.

    The researchers are still far from creating exercise in a capsule, but the early work published Tuesday in the journal Cell Metabolism has produced an intriguing clue. The small molecule, generated by muscles during exercise, helps convert normal energy-storing white fat to become energy-burning brown fat and increased blood sugar control in mice.

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    Dr. Robert Gerszten, director of clinical and translational research at the Massachusetts General Hospital Institute for Heart, Vascular, and Stroke Care, said that what excited the team about BAIBA, short for beta-aminoisobutyric acid, was that this molecule had been seen in the long-running Framingham Heart Study.

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    “The more BAIBA, the lower your insulin, the better your glucose, the less you weigh,” Gerszten said.

    The researchers did detailed studies of the molecule’s mechanism in cells in a dish and in live animals and found that it turned white fat into energy-burning brown fat. In mice, increased levels of BAIBA resulted in a slight weight decrease, decreased body fat, increased energy expenditure, and improved blood sugar. Then, in another study of people on an exercise program, they found that BAIBA levels increased after a 20-week exercise program.

    Carolyn Y. Johnson can be reached at cjohnson@globe.com. Follow her on Twitter @carolynyjohnson.