Q. I've heard "calorie restriction" diets can extend our life span. Do you recommend them?

A. There's some interesting research on calorie restriction, the practice of eating a very low-calorie diet and longevity. In animal studies, it's been shown to reduce the incidence of disease and indeed extend life. But what works in mice does not necessarily work in people, and there's very little known about such a diet's long-term impact on human health. In small clinical trials, people have shown short-term benefits in blood pressure, blood sugar, cholesterol, and heart rate. But there have also been negative effects, like reduced bone density, memory loss, anemia, and depression. And, moreover, such an extreme diet is very difficult to maintain and doesn't allow for much quality of life. Our healthy-aging goals, in my view, should not be to live as long as possible, but to live a good life as long as possible. To that end, I recommend eating sensible portions of a diet rich in fruits and vegetables, whole grains, and healthy protein -- and enjoying every bite.

Brent Ridge, M.D., is vice president for Healthy Living at Martha Stewart Living Omnimedia. Tune in to "Ask Dr. Brent" Thursdays at 1 p.m. on Sirius 112; e-mail brent@bodyandsoulmag.com.