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Faye Flam

Testing for ‘Fat Gene’? Results Could Be Worse Than Worthless

A new genetic test gives almost no insight into whether a person will become obese, but it might scare some people into really unhealthy choices.

Isn’t it always better to get tested than not? Think again.

Isn’t it always better to get tested than not? Think again.

Photographer: Patrick T. Fallon/Bloomberg

Like many genetic tests, a new one that uses several million genes to “predict” obesity is unlikely to do anyone’s health any good, and might do harm. The news of the finding, published in the journal Cell, looked like a good piece of science, with the potential to improve scientists’ understanding of why people exposed to the same or similar diets end up at very different weights. There’s also an important message to society – that obesity isn’t a failure of willpower. Some people have to struggle much harder than others to maintain a healthy weight.

The worrisome part was the suggestion – made by the tests’ inventors in numerous news stories – that this could be used to screen kids. Detecting health problems before they start is a major selling point for consumer genetics. But people may not recognize how inaccurate this test can be. In screening 300,000 people, the researchers found that only 43% those in the 90th percentile of obesity risk were actually obese, which is even less impressive considering that 40% of all Americans are obese.