Why Exercise Won't Make You Thin

You've heard it for years: to lose weight, hit the gym. But while physical activity is crucial for good health, it doesn't always melt pounds — in fact, it can add them. Here's why

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Whether because exercise makes us hungry or because we want to reward ourselves, many people eat more — and eat more junk food, like doughnuts — after going to the gym.

As I write this, tomorrow is Tuesday, which is a cardio day. I'll spend five minutes warming up on the VersaClimber, a towering machine that requires you to move your arms and legs simultaneously. Then I'll do 30 minutes on a stair mill. On Wednesday a personal trainer will work me like a farm animal for an hour, sometimes to the point that I am dizzy — an abuse for which I pay as much as I spend on groceries in a week. Thursday is "body wedge" class, which involves another exercise contraption, this one a large foam wedge...