Harvard Men's Health Watch

Obesity in America: What's driving the epidemic?

Obesity is a complex problem that scientists are still struggling to understand. In some cases, genetics seem responsible; in others, various combinations of hormonal, metabolic, and behavioral factors appear to play a role. But in most cases, it's hard to determine the exact cause of obesity.

It's difficult enough for a doctor to figure out why an individual patient has accumulated excess body fat. But what accounts for a worldwide epidemic of obesity? It's hard to understand how human genetics, hormone levels, or metabolic activity could change rapidly and simultaneously in millions of people, yet obesity has been increasing sharply throughout the industrialized world. In less than 40 years, the prevalence of obesity in the U.S. has increased by over 50%, so that two of every three American adults are now overweight or obese. Even worse, the obesity epidemic is rapidly spreading to our children.

Diabetes, hypertension, and heart disease are the most obvious consequences of obesity, but other results range from cancer, arthritis, and depression to kidney stones, fatty liver disease, and erectile dysfunction. All in all, obesity and overweight account for nearly one of every 10 American deaths, and they also drain our society of $223 billion a year.

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