Sweat More, Eat Better? Science Says Yes

Is there a correlation between the amount of time you spend at the gym and the number of calories you consume? Yes, according to a new study published in the International Journal of Obesity.

Researchers followed 2,680 adults who participated in aerobic exercise training for 15 weeks and found regular exercise was associated with changes in diet. Those who exercised at moderate to high intensities snacked less and were more apt to skip fried foods, processed meats and pasta in favor of eating more nutritious foods, including an increased intake of fruits and vegetables.

The connection between breaking a sweat and breaking up with empty calories didn’t surprise study co-author Molly Bray, PhD, a professor at the University of Texas at Austin.

Although it’s unclear how regular exercise influences eating habits, Bray explains that exercise stimulates neurotransmitters in the brain like dopamine and serotonin that could influence activity levels and eating behavior. (In contrast, low levels of dopamine and serotonin are linked to depression, which could cause emotional eating).

“But people also consciously change their behavior as they experience positive effects like more energy and a fitter body that could also have contributed to the positive change,” Bray adds.

There is also a psychological component: The attitude and skills it takes to start and maintain an exercise program are similar to those required to trade junk foods for healthier options. Thanks to a scientific principle known as a “transfer effect,” making one positive behavior change makes it easier to make another.

“When exercise becomes a habit or part of your lifestyle, [it takes less mental energy to hit the gym], allowing you to put more effort into eating more fruits and vegetables,” says Dr. Wasantha Jayawardene, PhD, assistant research scientist at Indiana University.

Jayawardene was the lead author of a study published in the Journal of the American College of Nutrition that found connections between increased physical activity and higher consumption of fruits and vegetables.

The results, he notes, are important because previous studies found that, compared to those who ate fresh produce just once per day, adding an extra serving of fruits and vegetables decreased stroke risk, heart attacks, cardiovascular disease and all-cause mortality.

Eating a vegetarian diet that emphasized fruits and vegetables was also associated with up to 43% reduced risk of developing obesity, according to a 2017 study.

“Using this natural phenomenon [that exercising leads to a healthier diet] likely could help you reduce the need for future intensive weight-loss interventions,” Jayawardene says.

Unlike conventional diets, which Bray believes are associated with deprivation, adding exercise and extra helpings of fruits and vegetables feels like a positive change that, in turn, can lead to additional positive healthy behaviors.

“Exercise can have positive effects beyond just increasing calories burned,” she says.