Blinding Light

The Blinding Distraction of BMI and Weight Loss in Obesity

Obesity care is suffering from a blinding distraction – BMI and weight loss. It’s not hard to find critiques of this. The American Medical Association recently cautioned physicians against the misuse of BMI as a surrogate for health and obesity. PLOS One has a new paper telling us BMI may not necessarily increase mortality independently of other risk factors in adults – especially in older adults. Health professions need to look beyond BMI, say the authors – to weight history, body composition, and complications of obesity.

Yet, as a practical matter, this is hard to do. Body weight is easy to measure. Weight loss is an outcome that many people with obesity really, really want.

Muscle Mass Matters

Caroline Apovian, Co-Director of the Center for Weight Management and Wellness at Brigham and Women’s Hospital and Professor of Medicine at Harvard, tells us:

“Paying attention to muscle mass and body composition is absolutely critical as we treat obesity. We need a greater focus on outcomes beyond BMI, especially as older persons start using GLP-1 medicines. Protecting muscle mass in the patients is very important.“

This is why Apovian is collaborating on new research with William Evans, who was the first to describe sarcopenia – the age-related loss of muscle mass and strength. Knowing that muscle mass is an important marker for longevity explains much about the limitations of BMI for understanding health in people with obesity.

If you want to know why Lilly was willing to put up two billion dollars for a potential obesity medicine that protects muscle mass, this is it.

The Exercise Factor

This is also a key reason to pay attention to physical activity in obesity care. It can be an important factor for maximizing the benefits of bariatric surgery. Even for people who only find time for moderate and vigorous physical activity on weekends, new research this week in JAMA tells us it has real benefits for cardiovascular health. This means that every minute counts for improving health with physical activity – there’s no such thing as wasted time for physical activity. Most important, exercise can be an important tool for preventing the loss of muscle mass.

So indeed, we need to look past the blinding distraction of weight loss and BMI in obesity. Because if good health and longevity is the goal, then preserving muscle mass deserves our attention.

Click here for the new research in PLOS One, here and here for the new papers in JAMA.

Blinding Light, photograph by Andrew Moua for the U.S. Air Force / Wikimedia Commons

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July 20, 2023

One Response to “The Blinding Distraction of BMI and Weight Loss in Obesity”

  1. July 20, 2023 at 10:06 am, Allen Browne said:


    Obesity is a disease of the energy regulation system (ERS) that can lead to unhealthy amounts and areas of adipose tissue. Controlling these unhealthy amounts and areas of adipose tissue controls the over 200 complications of the disease. However, changing the ERS changes the easiest ways to measure the disease – amount and areas of adipose tissue – but rarely is the problem with the ERS cured. Abnormal amounts of adipose tissue are easy to see. Malfunctions of the ERS are not easy to see when they are controlled with AOM’s, MBS, or combinations of AOM’s and MBS. Obesity is complicated.