7 Steps to Staying Slim and Healthy

Most Americans gain two pounds per year in midlife; even runners gain 3.3 pounds per decade, reports the National Runners' Health Study. It's easier to keep weight off than to lose it, so successful losers from the National Weight Control Registry weigh themselves often to spot pound creep, then take action.

It's a surefire way to increase your weekly calories out. Do it by adding a half-mile warmup and cooldown to every run, or simply by taking more walk breaks to increase the time on your feet.

Researchers found runners who rated their race as fun were more likely to choose a healthy bar over a chocolate bar when offered a post-event snack. The expert take? "Listening to music during a run or watching a video [on] a treadmill may be more related to weight-loss success than previously thought."

After you run, drink water and maybe eat a little fruit. And that's it. Otherwise, you're likely to go overboard. "Most people are very bad at estimating how many calories they consume," notes Pennington's Leanne Redman, Ph.D. "You have to be careful not to over-reward yourself after a workout."

Your metabolism slows with age in large part because you lose muscle mass. Muscle itself doesn't burn many more calories, despite common thinking. But it keeps you moving, and movement burns calories.

Apps and wearable tech that tally things like mileage, calories burned, and sleep time can help guide, reinforce, and reward your weight-loss efforts. "It might even help us show people that exercise is more palatable—more fun—than calorie-restricted diets," says Pennington's Robert Newton, Ph.D.

Obesity has been shown to act like the flu: If a lot of people around you are overweight, you face an increased risk of catching their disease. Surrounding yourself, physically or virtually, with healthy people can inoculate you. Join a run club or an online group focused on weight loss and/or fitness goals.