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Lisa Walford considers her current weight of 82 pounds to be just about optimal.
Granted, it's not easy to maintain. For much of her adult life, Walford, a petite 4'11", hovered around 95 pounds. Sustaining her new weight requires consuming only about 1,300 calories on most days, 15 percent less than what she used to eat.
But 50-year-old Walford, who admits her appearance could be considered gaunt, says the health benefits of her diet make it worth following. As a devotee of a diet movement called caloric restriction, or CR, she believes that consuming less will allow her to live longer. It's a notion she learned from her father, CR pioneer Roy Walford, and one she's comfortable sharing with a national audience.
"I was on Good Morning America, and Diane Sawyer said 'You look so thin. Are you really healthy?'" recalled Walford, who made media rounds this summer to promote her new book The Longevity Diet, co-authored with fellow CR practitioner Brian Delaney. Her response to such queries, she said, is usually the same: "We tend to associate health with external cosmetics, but I tend to think of the internal cosmetics.... People on CR are very internally healthy."
With the oldest members of the baby boomer generation about to turn 60, demographic trend watchers aren't surprised to see a rise in interest surrounding diet and health pursuits associated with extending life expectancy.
Myriad diet books on the market promise age-reversing effects through such techniques as copying the culinary habits of Okinawans, studying one's DNA or downing voluminous amounts of supplements and eating plenty of fruits and veggies. But caloric restriction, an age-extending technique that has been shown to work quite well on mice and other organisms, is an increasingly popular option.
Walford estimates that more than 2,500 people currently belong to one of two popular online CR forums, the Caloric Restriction Society and the CR Support Group e-mail list. Message-board topics range from a study linking Alzheimer's disease and insulin levels to the health effects of a caveman-style "paleo" diet, to the question of whether it's important to eat breakfast even if one isn't hungry in the morning.
Eating guidelines are also abundant. Since CR practitioners eat few calories, adherents believe it's necessary to pack as many nutrients into their meals as possible and to avoid starchy, processed foods. One menu representative of a typical 1,500-calorie meal plan features foods like salmon, egg whites, nonfat yogurt and vegetables.
CR fans say the emphasis on nutrition and the fact that they pursue the diet for health reasons makes it quite different from eating disorders like anorexia nervosa, which stem from a fixation on body image.
But Merryl Bear, director of the Canadian National Eating Disorder Information Center, says many people who talk about going on diets for health reasons are actually using such arguments to legitimize unhealthy fixations about food and weight.
"Some individuals who have eating disorders may use this theory as a way of justifying their food and weight preoccupation," Bear said.
Another argument against rigorous calorie-cutting is a lack of long-term studies indicating whether CR is linked to significantly longer human life spans.
Aubrey de Grey, a Cambridge University gerontologist, recently wrote a paper (.pdf) concluding that CR is unlikely to add more than two or three years to the mean or maximum life span. De Grey said he is skeptical of CR's potential for radical life extension in part because he sees no reason why it would be advantageous from an evolutionary perspective.
"Basically, there has been insufficient selective pressure for us to retain the ability to live 20 years longer than normal in response to nutrient deprivation," he wrote in an e-mail. De Grey added that he has no objection to moderate CR for health reasons, so long as practitioners don't expect to live a few decades longer as a result.
But moderate health benefits hardly seem to justify the effort of a CR diet, noted one contributor on the website Fight Aging, who wrote:
"What a trade-off: Feeling hungry your whole 80+3 years, or just enjoy your meals and die at 80."
Not even ardent CR supporters can accurately estimate how many years the diet might add to their lives, but most CR followers believe the diet offers potential for life extension much greater than two or three years.
Studies of mice, worms and other animals fed a restricted-calorie diet support the notion of radical life-extending benefits. A study of Labrador retrievers published in 2002 also found that a 25 percent restriction in food intake increased median life span and delayed the onset of signs of chronic disease in the dogs.
For humans, Walford prefers a more moderate regimen, in which people reduce caloric intake about 13 to 15 percent from their baseline level. The baseline is different for each person, based on the number of calories required to sustain a stable weight when one is neither undereating nor overeating.
As in all forms of dieting, however, there are people who take CR to an extreme. Walford said she does not advocate "serious CR," in which calories are reduced by around 30 percent, often with harmful effects.
"We do have people who have gone to the outer limit, where their body literally starts to metabolize their own organ meat," she said. "But that's serious CR, and all the media sensationalizes that part ... and then people discard the benefits (of moderate CR.)"
