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25 March 2011

The Biggest Loser: Classic Problem of Measurement Validity

The problem with The Biggest Loser is that they gauge progress in the wrong way. It’s not about weight loss; it’s about fat loss. They compare teams on that show by adding percentage-point weight loss. If they were only using aerobic exercise, that might approximate the contestants’ progress, but that’s not what they do. Instead, they focus on anaerobic techniques. Those tend actually to add weight in muscle mass. It is entirely possible—even probably—that a person engaged in such a regimen would become more fit, losing fat while adding muscle mass, gaining weight over all. If the producers of the show really wanted to encourage healthiness among their contestants and viewers alike, they would, instead of having weigh-ins, have dunk-ins, using an immersion tank to gauge body fat.

There is a big difference in the density of fat and muscle. In fact, given equal volumes of fat and muscle, the fat, ironically, will weigh about 15% less than the muscle. The only accurate way to determine a person’s density (and thus his/her ratio of fat to muscle mass) is to compare one’s volume to his/her mass. Mass is easy. Because the gravity on earth is relatively stable, a scale will do. Volume is a little more difficult. If you remember your middle school physics class (or Archimedes and the king’s crown), you’ll know that one can determine the volume of an object by submerging an object in a liquid and measuring the amount of liquid that is displaced. I, for one, think dunking contestants in a big tank is far more dramatic that making the numbers on a scale jump around arbitrarily while a person stands motionless on a platform.

I was an obese teenager. I ate a lot, and I ate calorie dense foods. Compounding that, I lived a sedentary life. I was content to sit on my ass, watching TV. If I had been pushed in the way that the people on The Biggest Loser are, it is unlikely that I would have lost weight as quickly as I had, and there is a really good chance that I would have given up. Given the stakes, I think the producers of the show owe their viewers a little more.

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