By By JoAnn E. Manson, M.D., and Peter WehrweinNewsweek Dec. 11, 2006 issue - Pendulum swin... Why Heavy Isn't Healthy...

Dec. 11, 2006 issue - Pendulum swings are common in medical research. So some people yawned-and others grinned-when they heard about recent studies that concluded being overweight isn't so bad for us after all. If only it were so. The truth is that numerous studies involving hundreds of thousands of patients followed for decades have shown that the risks for diabetes, heart disease, hypertension, stroke and even cancer are linked to being overweight or obese. And the more excess weight we have, the greater the risk for these diseases-and for an early death.

All this makes sense from what we now understand about fat tissue, especially the visceral fat tissue that accumulates deep in the abdomen, enlarging our waists in the process. It's biologically act-ive tissue that churns out hormones and chemical messengers that cause insulin resistance, inflammation and increased blood clotting. So when we gain too much weight around our middles, we're wreaking havoc on our health.

The studies that suggest that being overweight is OK have limitations. Typically, researchers compare the health of overweight people with the health of people who are not overweight, including some who are downright thin. But why are they thin? One possibility is that something is making them thin and putting their health at risk. Smokers are a prime example: they tend to be thin, yet they're also at increased risk of premature death. A second possibility is that thin people have lower weights because of an underlying disease, often one they don't yet know about. Many illnesses, particularly cancer, can cause weight loss, sometimes well before there's a clinical diagnosis. In other words, being thin may seem to be making people unhealthy when the situation is actually the other way around: poor health is causing thinness.

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