Exercise Will (Eventually) Stop Making You Hungry

When you start a new fitness program, you’re likely to notice that you feel better, sleep more soundly [2], and eat more. For those of us trying to lose weight, the last item isn’t helpful. That’s because you typically don’t just eat an extra apple or two. You’re so ravenous that you want to gnaw the kitchen counter first thing in the morning and eat every two hours thereafter.

But hark, hope: A new study suggests [3] that if you hang in there long enough, exercise might actually tame your appetite and make it easier to control how much you consume. This could give dieters new reason to stick to fitness resolutions—which the majority give up quickly [4] because of disappointing results.

A team of researchers from Australia, Great Britain, and Sweden monitored the appetites of 58 sedentary overweight and obese adults who participated in supervised exercise sessions designed to burn 500 calories five times a week. At the end of 12 weeks, the subjects predictably reported feeling hungrier upon waking than when they started their exercise regimens. However, their pre-measured breakfasts of cereal, toast, and tea surprisingly made them feel more full than when they ate them at the beginning of the study. More than half even felt less hungry throughout the day.

The study comes with caveats. Some participants were still hungrier than normal overall. They ate more at other meals and didn’t lose as much weight as their peers whose appetites were suppressed. The reason why exercise affected some participants’ appetites differently than others should be studied further. However, the evidence that long-term exercise can help us manage hunger—at the very least by making us more satisfied by food—is a welcome exception to the growing chorus [5] that stepping and squatting won’t help you lose weight. A 2006 review [6] of randomized, controlled trials on the impact of physical activity found that the majority led only to “modest” weight loss, because most people aren’t burning enough calories to move the scale. (Few studies mentioned exercise’s consolation prize: You can replace fat with heavier muscle mass and look better even if you’re not necessarily lighter.)

The basic problem is that it takes only a few squares of focaccia dunked in olive oil to cancel out the 300 calories you burned during a 30-minute session on the elliptical. In fact, it can be so hard to stay inspired that during one 16-month trial, more than half of participants paid to exercise dropped out. Also, alas, the notion that aerobic exercise boosts your metabolism when you’re off the treadmill might be a myth [7]. If all this isn’t enough of an endorphin-kill, another theory holds that exercise makes you so tired that your body retaliates by making you want to do as little as possible for the rest of the day to compensate for the energy you used up in your workout.

And yet it’s also increasingly clear that sustained exercise is essential for weight maintenance. About 90 percent of people [8] on the National Weight Control Registry, which documents the lifestyle habits of people who have lost at least 30 pounds and kept them off for a minimum of three years, claim they exercise about an hour every day. A new study of rats that were first fattened, then slimmed-down [9] found that sustained exercise over eight weeks helped them eat less and regain less, suggesting that the appetite-curbing mechanism works during maintenance, too. “Exercise didn’t eliminate the desire to overeat. It just reduced the magnitude of that desire,” explains Paul MacLean, lead author and assistant professor of medicine at the Center for Human Nutrition at the University of Colorado Denver. “The main benefit of exercise for long-term weight maintenance may be that it helps us stay on our diet, reducing those daily hunger pains that push us toward failure.”

Knowing that a dip rather than rise in appetite could be on its way eventually might help people suffer through the first sweaty months of an exercise regime. Perhaps weight-loss programs might include a “pre-diet” exercise period, so people wouldn’t expect to slim down at first and could start restricting their food later, when it would satisfy them more.

What if you’re one of the unlucky ones who has worked out religiously and is still starving all the time? MacLean says that’s no excuse to ditch your routine. He suggests some people might respond better to strength training, or they might need to ramp up the intensity of their workouts. Or they may simply need to be patient. In the meantime, take comfort in the other benefits of exercise: preventing heart disease and diabetes, reducing blood pressure and cholesterol, improving digestion, and making you more emotionally resilient [2]. Those can be motivation to keep at it. Still famished but determined to fit into your skinny jeans? A Denver omelet might have more staying power than cereal and toast.