Obesity rates continue to rise across the United States. The Centers for Disease Control and Prevention currently estimates that over 35% of American adults are obese. About 17% of children and adolescents are obese. What can you do to promote weight loss?

Numerous health risks are linked to obesity. They comprise some of the most common preventable causes of death, including coronary heart disease, type II diabetes mellitus, and strokes. In 2008, medical costs associated with obesity were estimated at $147 billion. Efforts to decrease obesity among adults and children are crucial from a public health standpoint.

Current Physical Activity Guidelines recommend 150 minutes (or about 30 minutes, five times a week) of moderate to vigorous physical activity per week. Specifically for weight loss purposes, many experts recommend longer durations of exercise – up to 60 minutes per day.

How much exercise is best for weight loss?

Are these longer periods of exercise necessary for optimal weight loss? Does the extra time increase fat loss? Or is there a compensation effect whereby the body adjusts to the additional exercise?

Mads Rosenkilde et al recently studied this question with a sample of overweight, sedentary Danish men. In a paper published recently in The American Journal of Physiology, the authors compared a group which performed 30 minutes of daily aerobic exercise for 13 weeks to one which performed 60 minutes per day.

The authors compared the groups based on body fat loss as well as negative accumulated energy balance, which they calculated from the changes in body composition.

Participants who performed 30 minutes of aerobic exercise per day experienced the same amount of body fat loss compared to those who performed 60 minutes per day. Surprisingly the overweight men who exercised 30 minutes per day had a much greater than predicted negative energy balance. There was no additional benefit obtained by doing 60 minutes of exercise per day.

The authors concluded that while one group of overweight Danish men performed twice the amount of daily aerobic exercise, the decrease in body weight and body fat was no greater than the group that performed half as much.

This study doesn’t fully explain why additional exercise might fail to provide any extra weight or fat loss. Possibly the longer periods of exercise cause these people to take in more calories. Possibly their bodies’ metabolic rates adjust.

Regardless, this study provides good news to overweight individuals who want to start an exercise regimen to lose weight and body fat. Since many of these people do not regularly exercise, starting with 30 minutes per day might be more appealing. They might be more likely to stick to the shorter programs.

In my opinion, any exercise is better than none at all when it comes to obesity and weight loss. While we need much more research to find ideal nutritional changes and specific exercise recommendations, we can at least start with moderate amounts of exercise each day.