While you were toiling away on the treadmill, a slow-burning debate among fitness experts was catching fire: Is exercise an effective strategy for losing weight? Or is the effort ultimately a wash, triggering hunger pangs that make you replace everything you burned and then some? A decade ago no one thought to ask this. Too much food makes you fat. Exercise burns calories. Ergo, exercise makes you less fat. Then research began to find that not everyone who exercises loses weight. Impossible as it may seem, some people actually gain a pound or two.
The problem: The range of individual responses to exercise is huge, says veteran weight-loss researcher Timothy Church, M.D., Ph.D., a professor of preventive medicine at Pennington Biomedical Research Center in Baton Rouge, Louisiana. "We don't understand all of it," he says. Fortunately, however, we understand enough to throw cold water on four of today's most insidious weight-loss myths.
The Secret to Shedding Weight Fast
MYTH 1: Exercise won't help you lose weight
That would be news to all the people who've lost double-digit poundage by pounding the pavement. But it would seem to validate the experience of your buddy who trained for a marathon and finished 2 pounds heavier. Dr. Church explains: "The degree to which you respond is probably dependent on genetics. Researchers have found 20 specific genes related to this, and how you score across those genes impacts your responsiveness." Your diet and the kind of exercise you engage in may play a role too. For most of us, the response is in the middle. Exercise, in fact, helps out in three specific belly-off zones.
Limiting weight gain—"A ton of data shows that leading a physically active life is critical for not putting on weight," says Dr. Church. Beyond the obvious calorie-burning rewards, regular exercisers become more attuned to their body's needs, reap mental benefits, and have a better quality of life, research shows. Regular workouts also help you maintain better body composition (more muscle, less fat), which means a lower risk of chronic diseases. (Search: How does exercise prevent disease?)
Losing weight—A recent Cochrane Collaboration review of 43 exercise and weight-loss studies determined that exercise helped people lose some weight—about 2 pounds. Crank up the intensity to "high" and you can lose 3 pounds—without dietary intervention. Our suggestion: Speed Shred, the new high-intensity follow-along DVD series from Men's Health.
Preventing the pounds from coming back—Losing weight isn't easy, but keeping it off is even harder, Dr. Church says. Your metabolism downshifts, and hormonal processes kick in to encourage your body to regain those pounds. The latest data from the National Weight Control Registry shows that people who successfully keep pounds off exercise for 45 to 60 minutes a day. And as long as you're not taking in more calories than you burn, daily exercise may remodel your metabolism, so your body burns more fat.
Fat blaster Intensity trumps all. You not only burn more calories while you're working out but also help your metabolism stay in a higher gear for hours afterward, thanks to a mechanism called EPOC, or excess postexercise oxygen consumption. In a recent study in Medicine & Science in Sports & Exercise, men who cycled hard for 45 minutes burned an average of 519 calories during the workout and another 193 calories in the next 14 hours. The tipping-point intensity level seems to be about 75 percent to 80 percent of your maximum heart rate (which is roughly 220 minus your age). (Video: 5 Exercises for a Hot Body)
MYTH 2: Exercise just makes you hungrier
Doesn't happen, at least in the short term, says David Stensel, Ph.D., who studies exercise metabolism at Loughborough University in England. In Stensel's 2010 study, people who exercised for 90 minutes ate just as many calories on the days they worked out as on the days they didn't. Numerous other studies have shown that vigorous exercise briefly down-regulates the appetite-stimulating hormone ghrelin. And while the blood levels of ghrelin rebound quickly after exercise, Stensel says they don't rise beyond where they were before the activity.