Cutting calories may slow down the aging clock as well as peel off pounds.

A labful of evidence has shown that feeding animals a healthy but low-cal diet for the long-term delays aging and increases lifespan. But suggesting this diet works in humans has been controversial, with a capital C, and difficult to study. A research team managed to test it and found that the same life-extending mechanisms that work in animals may occur in humans, too. Moral: Eat light, live longer. Bonus: You can throw out your fat jeans.

How might long-term low-cal eating extend lifespan? Put simply, it decreases blood levels of a hormone called T3, which regulates how fast you burn calories -- your metabolic rate. Low T3 slows metabolism, and that reduces the formation of free radicals, the destructive compounds that wreak havoc on cells and tissues.

The people in the study didn't starve; they ate a well-balanced 1,800 calories a day (versus 2,700 for a comparison group), and they kept it up for 3 years or more. They got at least 100 percent of the U. S. Food and Drug Administration's Recommended Daily Intake (RDI) for all the body's essentials by concentrating on nutrient-rich but relatively low-calorie foods, such as fruits, vegetables, soy and wheat proteins, egg whites, low-fat dairy products, and lean meats. Not surprisingly, the low-calorie group barely touched highly processed foods, simple sugars, refined carbohydrates, and saturated or trans fat.

While many studies have shown that healthy dietary and exercise habits decrease the risk of age-related illnesses (such as heart disease and diabetes), this particular study supports the theory -- long held by some -- that it takes a calorie-restricted diet to actually slow aging.

That said, it isn't easy to eat this way, year in and year out. But if extra time is more important to you than extra helpings or a regular Snickers fix, there's now evidence that calorie restriction may pay off in extended time on earth. To evaluate your diet, take the RealAge Nutrition Health Assessment.