Middle-age people who are overweight but have normal blood pressure and cholesterol levels are kidding themselves if they think their health is just fine.
Northwestern University researchers tracked 17,643 patients for three decades and found that being overweight in midlife substantially increased the risk of dying of heart disease later -- even in people who began the study with healthy blood pressure and cholesterol levels.
High blood pressure and cholesterol are strong risk factors for heart disease. Both are common in people who are too fat, and often are thought to explain why overweight people are more prone to heart disease.
But there is a growing body of science suggesting that excess weight alone is an independent risk factor for heart attacks, strokes and diabetes.
The new study fits with that evolving school of thought and contrasts with a controversial government study published last year that suggested excess weight might not be as deadly as previously thought.
"The take-home message would be pay more attention to your weight even if you don't have an unhealthy risk factor profile yet," said lead author Lijing Yan, a researcher at Northwestern and Peking universities.
The study appears in today's Journal of the American Medical Association.
Yan said it is possible that some overweight participants developed high blood pressure and cholesterol problems during the study, which could have contributed to their deaths. But she said researchers increasingly believe that being too fat causes other cardiovascular problems, too.
The study "will help define obesity as a disease" in itself, said Dr. Samuel Klein, an obesity expert at Washington University in St. Louis.
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