Credit: Polly Becker

When I was a destitute graduate student several years ago, I decided to earn a quick $75 by signing up for what sounded like a relatively innocuous clinical study. An I.V. in my left arm would feed precise amounts of glucose and insulin into my bloodstream, while from my right arm a nurse would periodically draw blood to test for glucose. The study would assess how effectively my body responded to sugar, a measure that predicts risk for developing type 2 diabetes.

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