WEST PALM BEACH, Fla. (Cox News Service) -- How low can you go when it comes to daily calories?

Researchers have long been drawn to the notion that people may extend their lives by substantially reducing the number of calories they eat.

This isn't such a crackpot idea. While reducing caloric intake results in weight loss, studies are beginning to show that lowering consumption also reduces body measurements that, when high, can cut lifespan short.

Two of those so-called biomarkers -- fasting insulin levels and core body temperature -- declined during a study done by the National Institute on Aging when those enrolled cut their calories by 25 percent for six months.

Similar eating habits have already been shown to extend lifespan in lab rats, but there is no definite proof it will do the same for humans.

That's all the more reason to check out the concept, which promotes balanced nutrition, and whose proponents distance themselves from eating disorders like anorexia. (Get more information about the Calorie Restriction Society at www.calorierestriction.org)

Such renowned health advocates as Dr. Andrew Weil, the bestselling author, are intrigued with the idea.

"My general sense is an ultra low-calorie diet is better for cardiovascular health," he told me, "but the brain may be more vulnerable to disease because we've found higher incidence of ALS (Lou Gehrig's disease) in people who are lean and athletic. "

(Dr. Roy L. Walford, the gerontology researcher who advocated and practiced calorie restriction as a way of life, died two years ago from complications of ALS.)

"I don't think it's craziness," Weil said of the concept.

"The animal studies are good."

And the co-author of a recent study on how obesity may reduce future life expectancy says he also thinks cutting back on calories isn't far-fetched.

"I have not seen an (NIA) study on caloric restriction," says Dr. S. Jay Olshansky, a longevity researcher at the University of Illinois at Chicago. "However, the U.S. population would certainly benefit from a more calorically restricted diet since it would likely reduce our risk of obesity-related deaths."

The results of the NIA trial, announced earlier this month, are encouraging. And the findings give more impetus to the launch of a bigger, two-year study, known as CALERIE (Comprehensive Assessment of Long-Term Effects of Reducing Intake of Energy) to be conducted at three different sites around the country.

Those sites are: Pennington Biomedical Research Center, Louisiana State University, Baton Rouge; Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Mass.; and Washington University in St. Louis.

Check the Web site -- calerie.dcri.duke.edu -- for further information.

The ultimate trip-up may be sticking with a very low-calorie diet, even if research proves that it can extend life. Many of us may be defeated by the less-is-more eating plan. We have long equated eating whenever and whatever we want with prosperity and comfort, and that may be hard to reverse.

Copyright 2006 The Cox News Service. All rights reserved.