Staying Healthy

Hidden causes of weight gain

Underlying conditions and subtle physical changes could be to blame.

By , Executive Editor, Harvard Health Letter

photo of a mature woman and man working out in a gym, each is doing exercises with hand weights

The reason for gaining weight isn't always a mystery. For example, you might know you've been eating more and exercising less, a potent combo that often results in extra pounds. But sometimes the cause isn't quite so obvious. And you might not be aware of many of the other factors that can contribute to weight gain.

Age-related causes

Getting older brings physiological changes that can affect weight. Chief among them is muscle loss. Starting in middle age, we lose about 1% of muscle mass per year, which affects strength and metabolism (how fast we burn calories). "Smaller muscles use fewer calories. If your diet doesn't change, you'll consume more calories than you need. The excess is stored as fat," says Dr. Caroline Apovian, an obesity medicine specialist and co-director of the Center for Weight Management and Wellness at Harvard-affiliated Brigham and Women's Hospital.

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About the Author

photo of Heidi Godman

Heidi Godman, Executive Editor, Harvard Health Letter

Heidi Godman is the executive editor of the Harvard Health Letter. Before coming to the Health Letter, she was an award-winning television news anchor and medical reporter for 25 years. Heidi was named a journalism fellow … See Full Bio
View all posts by Heidi Godman

About the Reviewer

photo of Anthony L. Komaroff, MD

Anthony L. Komaroff, MD, Editor in Chief, Harvard Health Letter

Dr. Anthony L. Komaroff is the Steven P. Simcox/Patrick A. Clifford/James H. Higby Professor of Medicine at Harvard Medical School, senior physician at Brigham and Women’s Hospital in Boston, and editor in chief of the Harvard … See Full Bio
View all posts by Anthony L. Komaroff, MD

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No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

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