Want to look good? Keep exercising.

Just keeping active can improve eating habits and make your waistline flatter.

WASHINGTON — Do your kids wear an activity monitor to track their time on the bicycle, treadmill or elliptical trainer? Chances are you won’t be exactly piling on the scale anytime soon. But recently, research has shown regular exercise can affect appetites and body composition as well as psychological health and well-being.

“Exercise has gone from anorexic to a really important part of health care,” said John Chappell, a sport psychologist at George Washington University. Exercise has long been recognized as beneficial to weight control, however. So finding evidence that it can positively affect eating patterns is something new, Chappell said.

The recent research “focuses specifically on what happens when you’re eating or eating at a particular time and the impact of being more active,” he said.

“Exercise really is one of the most powerful agents for boosting your emotional well-being and improving your behavior as you age,” added Adam Fagen, an associate professor of exercise science at Washington University in St. Louis. While it’s not uncommon for older people to see their appetite fall while they exercise, fitness behavior experts have yet to recognize that people younger than 50 will experience this effect, Fagen said. (No surprise given the American Heart Association’s recommendation that older adults to be at least 150 minutes of moderate activity each week.)

The big difference between older and younger people is that healthy young people want to eat less, eat healthier and reduce their waistlines while exercising, Chappell said. In contrast, most adults’ interest in weight control appears to dwindle after age 50 or 60, he said.

But just keeping active can improve eating habits and make your waistline flatter, according to two recent studies on postmenopausal women and adolescents. In the younger group, physical activity triggered the release of appetite hormones such as leptin and ghrelin in a way that made people think they needed fewer calories to feel satisfied. That proved to be especially true for low-calorie energy-dense foods such as baked potatoes and fast-food chicken nuggets, Chappell said.

Activity usually has an effect on appetite that’s much more subtle than calorie-cutting, Fagen said.

Fagen surveyed some 2,800 college students for the study, comparing those who reported eating more to those who ate less. He expected students who consumed more energy dense foods would exercise more and eat fewer calories — a phenomenon known as energy restriction, or food restriction. But that wasn’t the case. The ones who ate more eat less, but the do so more briskly.

So who’s exercising and who’s eating? Some of the most typical exercisers — active women between ages 25 and 45 — are “out-of-shape” meat and potato eaters who don’t exercise and don’t feel hungry for large amounts of calories, Fagen said.

In the second study, published in 2012 in the Journal of the Academy of Nutrition and Dietetics, researchers asked 15 adults, age 46 and younger, to exercise for 30 minutes two or three times a week for three months. The goal: to increase endurance and decelerate heart rate, for an aerobic workout that will help increase their stamina. But the participants told researchers they didn’t know how much exercise they were getting or would be exercising.

Half of the adults were told to exercise for an hour, but they didn’t get that much; the other half got information about what their dose was — a dose between 140 and 150 minutes of moderate-intensity exercise. Participants also reported eating a variety of healthy snack foods.

Over a nine-week period, when researchers reported on how many calories were consumed per week, those who exercised more exercised more. (That’s consistent with other studies showing physical activity can motivate you to eat healthier at home rather than at a busy restaurant.)

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