Exercise, which burns calories, should make you hungry, right? Not exactly. Writing in the New York Times, Gretchen Reynolds explains that exercise does in fact, boost the production of ghrelin, a hormone that tell us that we want food. But wait, here comes the strange part. Reynolds cites a 2012 study from the University of Wyoming, for which a group of women either ran or walked and, on alternate days, sat quietly for an hour. Yes, the researchers found that those who ran produced more ghrelin, but the same group also ate fewer calories than they burned. Why? Because, the researchers believe, exercise also boosts the production of other less understood hormones that tell the body that it doesn’t really need more food. Reyolds cites a second study published in December that found that after 12 weeks of jogging, formerly sedentary, overweight men and women began recognizing, without consciously knowing it, that they should not overeat. Reynolds quotes Catia Martins, study author and a professor at the Norwegian University of Science and Technology in Trondheim, saying exercise “improves the body’s ability to judge the amount of calories consumed and to adjust for that afterward.” Running, says Martins, does that better than walking, and the longer you do it, the more better it works.