The research compared risk factors for cardiovascular disease—like blood pressure, heart rate, and cholesterol levels—in three groups of overweight volunteers who were all tasked with losing 7 percent of their body weight over a period of 12 to 14 weeks. One group did this by eating 20 percent fewer calories than usual, one group got 20 percent more physical activity than usual, and one group did both, eating 10 percent less and moving percent more.
In the end, all three groups showed similar improvements. In fact, each strategy was expected to reduce lifetime risk of developing cardiovascular disease from 46 percent to 36 percent.
The findings, published this week in the American Journal of Clinical Nutrition, surprised lead author Edward Weiss, Ph.D., associate professor of nutrition and dietetics at Saint Louis University. He expected to see positive changes in all groups, but thought that those who combined diet and exercise would reap even more benefits than those who did just one.
“When you think about it, the body’s responses to exercise and to calorie restriction are completely different,” says Weiss. “Exercise makes your heart rate go up, your metabolism go up; it’s quite a dramatic process. On the other hand, cutting calories really slows things down. In severe cases, it’s been described as quasi-hibernation.”
He suspected, then, that each process would provide different benefits for heart health—and that the group that diWant d both “would get the best of both worlds.”
While that didn’t happen, Weiss is quick to point out that a large part of cardiovascular disease risk can’t be accounted for by “traditional” risk factors. So it’s still possible, he says, that combining diet and exercise has additive effects that simply weren’t measured in this study. And even though his experiment couldn’t support the argument for a diet-plus-exercise approach to weight loss, other research certainly has—including a 2015 study he co-authored on diabetes risk factors.
In other words, these findings may be good news for people who are able to lose weight despite not eating as well as or exercising as much as they should—but they’re not an excuse to be lazy just because you’re on a diet, or to pig out on junk food just because you work out. Weiss still believes that combining a healthy diet and getting regular exercise is still best for overall health.
It may also be the easiest way to lose weight and keep it off. In the study, people in the combined-intervention group got to their target weights sooner than those in the other groups, despite the researchers’ attempts to keep them all evenly paced. And unlike the diet-only or exercise-only groups, no one in the combo group dropped out before the study’s end.
“We tend to focus on putting exercise and dietary interventions head-to-head, but really we should be using all the tools in the shed,” Weiss says. He does caution, though, that people should be mindful of their calorie consumption once they start working out: “You don’t need to start drinking Gatorade or eating nutrition bars, or rewarding yourself with cheesecake just because you’re exercising.”
Overall, Weiss says, this study should provide hope to anyone who’s overweight and wants to make a change. “The biggest message here is that people should use the approach that’s most amenable to them,” he says. “If they like healthy eating and a low-calorie diet and they hate exercise, get them going on the diet program; there are huge gains to be made no matter what.”