Maybe you've heard the recent downer reports that exercise won't make us thin because it makes us hungry, particularly for junk food. Or could be, you've noticed firsthand that you eat a lot more on gym days than on days off. Either way, it raises the question: If working out only sets us up to blow our diet, what's the point?
For starters, some research suggests exercise doesn't always cause hunger but can curb it. "Exercise may lower levels of ghrelin, a hormone that stimulates appetite in the short term, while raising levels of peptide YY, a hormone that suppresses appetite," says study author David Stensel, Ph.D., reader in exercise metabolism at Loughborough University. That's only if the workout is intense (if you can chat, forget it), but the more intense it is, the longer the benefit seems to last. "It may be that your body needs to circulate more blood to prevent overheating," Stensel explains. Because eating would cause blood to flow to the stomach instead to aid digestion, your body dampens your appetite to prevent that.
Like all good things, this satiating effect ends—about an hour later, when your body starts to crave the energy it used up. And unfortunately, the desire to refuel may hit women harder than it does men. "Physical activity may raise concentrations of longer-term appetite-stimulating hormones like insulin and leptin in women," says Barry Braun, Ph.D., associate professor of kinesiology at the University of Massachusetts in Amherst. What's up with the sexist hunger hormones? "It might be that women are wired to defend their body weight to preserve energy for pregnancy and lactation," Braun says.
Here's where frequent exercise can save the day (and our waistline). "It appears to help restore sensitivity to brain neurons that control satiety," says Neil King, Ph.D., professor of human movement studies at Queensland University of Technology. In other words, the more you do it, the more in tune you become with your hunger signals, which may aid in offsetting them. More motivation to sweat regularly: It can lower heart disease risk, lift mood and up your odds of a longer life overall, whether you lose weight or not. Add to all that a bangin' bod, and a passing case of tummy growls is no biggie.
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