Exercise plays only a limited role in weight loss without broader lifestyle and nutritional changes. Provided to China Daily

If you are spending more time running, walking or pumping iron in the gym and still not losing weight, fitness experts say it could be because you are having too big a reward for too little exercise.

Although fitness has indisputable health benefits, it takes a lot of walking or running to burn off the calories in a donut.

"There's a war between exercise and nutrition in our heads," says American Council on Exercise spokesperson Jonathan Ross. "People tend to overestimate the amount of physical activity they get. They work out a little bit and treat themselves a lot."

Ross, a personal trainer based outside Washington DC, says exercise can play a role in weight reduction, but without broader lifestyle and nutritional changes, that role is limited.

"We put exercise in a box and once that exercise box is filled in we don't do much the rest of the day," he explains, adding that a post-workout calorie-dense treat doesn't help.

"Some (weight-loss) programs stress nutrition, some stress exercise," he says. "But the two together are greater than their parts."

The National Weight Control Registry in the United States, which gathers information from people who have successfully lost at least 13.5 kg and kept it off for a least one year, reports that 90 percent of its members exercise, on average, about one hour per day.

US health officials recommend that healthy adults get at least 150 minutes of moderate-intensity physical activity a week, or around 20 minutes a day.

Joseph E. Donnelly, an exercise physiologist with the American College of Sports Medicine, says the US government guidelines are for cardio vascular fitness, not weight loss.

"It was never intended for weight management," says Donnelly, a researcher who focuses on obesity at the University of Kansas. "People have misused it."

He adds that studies suggest 250 to 300 minutes of exercise per week may be the minimum to lose weight.

Donnelly says if there's a success story for the role of exercise in weight control, it's in maintenance.

"Even among the naysayers who feel you can't lose much weight through exercise, most people agree it seems important to maintain weight," he says.

Michele Olson, professor of exercise physiology at Auburn University Montgomery, in Alabama, says it is difficult to shed pounds through exercise alone.

She adds that people must be physically active regardless of their size or whether they are losing weight.

"Moderately intense exercise done in as small as 10-minute increments two to three times a day markedly reduces our risk of all causes of mortality, heart disease most effectively but all other causes, including cancers, deaths due to hypertension and strokes," she says.

Ross says for many of his clients the goal is to maintain vitality and capability.

"For anyone out there who is frustrated about not losing weight, try to focus instead on what you love about your life," he says. "The No 1 goal is to feel better in your body. That's what exercising is good for."

Reuters