It’s also important to remember one essential fact about exercise and weight loss, says Slentz. “Exercise by itself will not lead to big weight loss. What and how much you eat has a far greater impact on how much weight you lose,” he says. That’s because it’s far easier to take in less energy (calories) than it is to burn significant amounts and it’s very easy to cancel out the few hundred calories you’ve burned working out with just one snack.

Health.com: 10 Superfoods for Weight Loss

Where exercise appears to matter most is for preventing weight gain, or for keeping off pounds once you’ve lost weight, says Slentz. “Exercise seems to work best for body weight control,” he says. The National Weight Control Registry, which since 1994 has tracked more than 10,000 people who shed an average of 66 pounds and kept it off for at least five years, would agree. Ninety percent of successful weight loss maintainers exercise for about an hour a day and their activity of choice is cardio, simply walking.

This article originally appeared on Health.com