If you can't bring yourself to hit the gym, there may be another way to generate some of the benefits of exercise, though we can't promise you'll like it. A study of the way the body's brown fat (BAT) responds to exercise found similarities to what occurs when exposed to cold, suggesting the two may sometimes substitute. It's old news that exercise has a positive effect on cardiovascular health and triglyceride levels in the blood, as well as helping to regulate weight. The mechanisms are less understood. Harvard's Dr Laurie Goodyearand Dr Kristin Stanford of Ohio State University tested the effects of 40-45 minutes of moderate intensity exercise on blood molecules. Most molecules tested decreased with exercise, but there was an increase in concentrations of the lipid 12,13-dihydroxy-9Z-octadecenoic acid (12,13-diHOME), which they think induces at least some of the positive health effects. Goodyear and Stanford reported in Cell Metabolism that 12,13-diHOME jumped, irrespective of participants' usual levels of physical activity, age or sex. Previous work has shown 12,13-diHOME is released by BAT, which burns calories. "These data highlight another mechanism for the beneficial effects of exercise," Goodyear said in a statement. Moreover, 12,13-diHOME concentrations were demonstrated last year to rise on exposure to cold. Putting the two facts together could help us understand more about the body's metabolism, as well as indicating cold exposure can be good for those who can't get enough exercise. "Most data have suggested that cold and exercise have opposite effects on BAT, so to see that 12,13-diHOME was released from BAT after both exercise and cold exposure was unexpected," said Stanford. However, the behavior is not identical. In cold conditions BAT burns calories directly to keep us warm, but during exercise, it signals to muscles to take up fatty acids, which they burn instead. We are born with high levels of BAT, which infants burn for warmth. Bears build up great stores for hibernation. Humans retain a small amount into adulthood, a fact that was only recently confirmed, demonstrating how poorly understood it remains. Exercise, whether short or long-term increases 12,13-diHOME levels in mice, Goodyear and Stanford found, except when the rodent's brown fat was surgically removed, confirming the relationship. Together, these findings indicate stored white fat breaks down to become circulating fatty acids in the bloodstream, with the known health effects, while brown fat releases 12,13-diHOME during exercise to assist skeletal muscles in taking up these fatty acids. The authors are planning further experiments to explore the similarities and differences between cold exposure and exercise, and to find out whether there are other ways to stimulate 12,13-diHOME release. In the meantime, however, it's possible turning the heater down could be the path to better health. Source
