We all know someone who can eat and drink whatever fatty, sugary, carb-loaded food is put in front of him, doesn’t seem to do much exercise, and yet never seems to put on an ounce of weight. “I just can’t help it,” he’ll say with wide-eyed innocence, while others quietly seethe.

It turns out that he may be right. A new BBC documentary explores the idea that some people seem to have a genetic predisposition to skinniness. On the show, 10 thin people were asked to gorge on junk food for four weeks while also cutting back on any aerobic activity, even walking. Copying an experiment carried out in a Vermont state prison in 1967, the program produced much the same results: It seems that some people just can’t put on weight, no matter how much they eat or how idle they are.

The next question: How long until we can all get our hands on these genes? Burger King and La-Z-Boy are probably working on it as we speak.

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