Are people with high BMIs unhealthy?

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Many American companies have been using BMI as a shortcut to assess their employee’s health status? This approach makes sense, right? Public health agencies often detail the severe health consequences of overweight and obesity. The US Public Health Service Task Force guidelines state that patients with obesity should receive intensive weight loss counseling. Even the American Medical Association calls obesity a “disease.”

Despite this, a sizable number of those with high BMIs have completely normal cardiometabolic functioning. In other words: they’re overweight/obese and otherwise and healthy.

These are the findings of a recent report from colleagues at UCLA. They found that nearly 50% of people with overweight and almost 30% of those with obesity are, in fact, metabolically healthy.

This finding is being interpreted as “the final nail in the coffin” for BMI. There’s no question in my mind that BMIs demise would be welcome to many (in my experience, people love to assail BMI as non-specific, not relevant to specific groups, and a poor measure of fatness — some days, I agree).

But, I suspect the reports of BMIs demise are greatly exaggerated.

The idea of being metabolically healthy while obese is not a new one. Although the size of the metabolically healthy population is a mater of some debate, their existence is well accepted.

But here’s the thing that the recent study didn’t consider: time.

There’s some evidence that people’s likelihood of being obese and healthy drops as they age. Put another way, wait enough time and obesity will start having negative health effects. There’s also emerging data suggesting that the time spent in obesity — literally the number of years that someone spends in an obese state — is independently associated with negative outcomes. This is a particularly potent health risk since very (very) few people with obesity ultimately lose weight (and keep the weight off).

So, it’s true: companies that want to quickly assess employee health probably shouldn’t use BMI. But, if they want to make predictions about future health risks, BMI might be a helpful tool.

h/t @qz