Maybe the old saws about Russian monks living to be 100 on nothing but yogurt have a small bit of truth to them. New research finds that a restricted calorie diet actually increases life span and reduces free radical production in our cells.

The calorie restriction diet has been around for awhile, and this new study simply confirms that it works at least in theory. The basic idea? Gradually reduce your calorie intake by 15-30 percent over time -- 1,800 daily calories instead of the 2,500 recommended for an adult male by the FDA -- by eating lots of veggies and avoiding saturated fats and chemicals.

Hard-core CR fanatics often weigh their food on a scale and run their meal plans through software designed to ensure their getting the right nutrients. The danger of eating this way without carefully measuring and calculating is essentially anorexia, which is far less healthy than overshooting one's calorie goal for a day. Lose weight too quickly or fail to get enough salt or other essential vitamins and minerals, and health benefits fall away and the risks mount quickly. For instance, while CR has been found effective in reducing atherosclerosis (hardening of the arteries), rapid weight-loss reduces muscle mass and could shrink the heart, heightening the risk of a heart attack from overexertion. Reduced bone density and osteoporosis, anemia, memory loss and dizziness are among the other risks.

In fact, some critics see CR as little more than scientifically backed anorexia -- or something teetering on the verge of it. It's worth taking a look at this fascinating in-depth feature from New York Magazine from a couple years ago to get a picture of what living the calorie restricted lifestyle can be like. Judge for yourself if you think living a couple years longer is worth the work -- and the risks.