How Much Exercise to Prevent Weight Gain?

In the relationship between exercise and weight, one article of faith has held up for years. Exercise is a valuable tool for preventing weight gain. Though you can’t outrun a bad diet, experts are quite clear that exercise helps to maintain a lower weight. However, a new randomized study in Obesity asks a key question. How much exercise does it really take to prevent weight gain?

The answer: maybe not as much as we’ve been thinking.

A Randomized 12-Month Study

Richard Washburn and colleagues tested three different durations of exercise for maintaining a five percent weight loss over a period of 12 months. In the minimum exercise group, the assignment was 150 minutes per week. The other two groups had assignments of 225 and 300 minutes per week. In the end, the researchers did not find a benefit for doing more exercise:

“This study found no evidence for an association between the volume of moderate‐to‐vigorous–intensity exercise and weight regain across 12 months following clinically relevant WL. Further, results suggest that exercise volumes lower than those currently recommended for WL maintenance, when completed in conjunction with a behavioral weight‐maintenance intervention, may minimize weight regain over 12 months.”

Yes, But

It is worth noting that absence of proof is not proof of absence. This was a good study asking a question that had not really been tested in a rigorous way before. However, it was small – 76, 79, and 80 subjects in each of the three groups. What’s more, people in the top group did not really follow through with 300 minutes of exercise per week. Their weekly average was only 179 minutes.

The researchers acknowledge this limitation. When the prescription for exercise goes up, adherence goes down. It may be that higher amounts of exercise could be helpful. Indeed, this is what observational studies suggest. But in the real world, those higher volumes of exercise might not be achievable. Time is a precious resource for people with busy lives.

Rethinking Recommendations?

Over and over again, we hear the laments. People are just not getting as much exercise as they should to prevent weight gain. If it’s not automatic, we tend to resist exercise. So perhaps some of the energy that goes into urging people to exercise more should be redirected. Rethinking our physical environment to make physical activity more routine might be more helpful.

Click here for the study and here for a systematic review of physical activity and the built environment.

Exercise, Stretch, Discuss, photograph © filtran / flickr

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January 11, 2021