Trying to lose weight and frustrated the pounds aren't dropping off after all those extra workouts you are putting in? A new study may brighten your day.

First, the good news. Exercise can by itself result in weight loss.

Now, the bad news. You're probably not exercising enough.

The new study, published in June in the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, debunks the long-held theory that exercise alone is not enough to help someone shed unwanted pounds. Cutting calories has always been the key to success.

Scientists from the University of North Dakota and other institutions divided 31 sedentary men and women into two groups. One group exercised five times a week by walking briskly or other similar exercise for 30 minutes to burn about 300 calories a day, for a total of 1,500 calories a week. The other group doubled the duration of their exercise to burn about 600 calories a day for a total of 3,000 calories a week, the New York Times reported. Neither group was asked to change their diet. Their activity was tracked using wearable monitors.

At the end of 12 weeks, the participants that burned about 300 calories per day lost little, if any, body fat. Some were even heavier.

But the participants that did twice as much activity were thinner.

Both groups compensated for some of the lost calories by adding back about 1,000 calories a week, the researchers reported. How the volunteers compensated was not clear, Kyle Flack, an assistant professor at the University of Kentucky, told the New York Times. But he believes overeating may have been the culprit.

The more active group totaled a weekly deficit of about 2,000 calories, compared to 500 calories for the less active group, which was determined to contribute to their weight loss.

"It looks like you can lose weight with exercise," Flack told the Times. But, he said, "you still have to count calories and weigh portions" if you hope to use exercise to control your weight.

But not all experts agree.

"I think the role of exercise in weight loss is highly overrated," Marc Reitman, chief of the diabetes, endocrinology and obesity branch of the National Institute of Diabetes and Digestive and Kidney Diseases, told the Chicago Tribune in 2017.

"I think it's really great for being healthy, but I'm a strong believer that overeating is what causes obesity. To exercise your way out of overeating is impossible," he said.

A 2017 study in the journal Applied Physiology, Nutrition, and Metabolism by researchers at Bangor University in the United Kingdom concurred. They found that women who did not alter their diet failed to lose any weight even if they engaged in exercises classes three times a day.

In the U.S., nearly 40 percent of adults are obese, according to the most recent estimates from the Centers for Disease Control and Prevention.

The CDC recommends that adults get 150 minutes of moderate-intensity aerobic activity, or 75 minutes of vigorous-intensity activity, or an equivalent combination a week. In addition, the agency recommends two or more days a week of muscle-strengthening activities that are moderate- or high-intensity and involve all major muscle groups.