The science behind starvation diets
Published: Tuesday, January 31, 2006 at 11:54 a.m.
Last Modified: Tuesday, January 31, 2006 at 11:54 a.m.
Every morning, Brian Delaney scarfs down an 800-calorie breakfast of cereal and granola, yogurt, blueberries, almonds and other fruit. "I love stuffing my face when I wake up," says Mr. Delaney. "I feel very full."
While Mr. Delaney may sound like a binge eater, the 42-year-old writer is a proponent of a practice known as "calorie restriction." He limits his daily calories to about 1,950 - about 550 less than other active men his size.
New research shows that calorie-restriction diets - which cut calories by as much as 40 percent of your normal intake - may help you live a longer life. Earlier this month, one of the first human studies of calorie restriction showed that people on the strict diet had younger hearts than normal-weight people on a typical Western diet.
While calorie restriction may not be practical or possible for everyone, there are still lessons to be learned. What is so surprising is that people who follow calorie-restriction diets in hopes of living longer are still eating a lot of food. They indulge in huge breakfasts and big dinners, but eat few or no snacks in between. The main difference in their diets compared with most people typically is in the nutritional quality of food they eat - whole grains, fruits and vegetables and less animal protein and saturated fat. They avoid refined foods, sugary desserts, soft drinks and other sources of "empty" calories.
Calorie restriction to slow aging is practiced in a variety of ways. The mild form involves about a 10 percent to 15 percent reduction in daily calories beyond what a person would normally eat to maintain weight. This is similar to a standard weight-loss diet - the main difference is that the eater sticks to it permanently.
More-serious calorie restrictors reduce their daily caloric intake by as much as 40 percent. For instance, a six-foot, moderately active, 180-pound man normally would eat about 2,640 calories a day. If he practices calorie restriction, his daily calories could drop to just 2,370 or all the way down to about 1,585. Although people who practice calorie restriction, typically lose weight at first, eventually their body and metabolism adjust and the weight loss stops, despite the low calorie level.
Even though they are eating fewer calories, calorie-restriction dieters say they consume large quantities of bulky foods like fruits, vegetables and whole grains that fill them up and stay with them longer. Calorie restrictors typically budget their calories over two to three days - that means a man adhering to 2,000 daily calories would think in terms of 6,000 calories over three days. That way more can be eaten at a business dinner or a family celebration, and the dieter can make up for it in the next few days.
Calorie restrictors say the plan takes discipline, but it isn't a "starvation" diet. Hunger can be a problem, but most calorie restrictors learn how to fill up on low-calorie foods.
The full risks and benefits of such a diet aren't yet known. Calorie restriction might hinder the body's ability to fight infection. Long-term adherence results in low body fat, which can mean feeling cold or discomfort while sitting on hard surfaces. The diet may lead to menstrual irregularities and a lower libido. Many calorie restrictors have regular blood tests to monitor nutritional health and also take vitamin supplements.
The calorie-restriction concept stems from a growing body of scientific evidence that reducing calories without compromising nutrition can help slow the aging process. This month, a study in the Journal of the American College of Cardiology looked at the heart function of 25 people who had practiced calorie restriction for about six years. Mr. Delaney was among the study participants. The participants ate between 1,400 and 2,000 nutritionally balanced calories a day. They were compared with 25 people on a typical Western diet of about 2,000 to 3,000 daily calories.
The researchers, from Washington University in St. Louis, used ultrasound exams to study heart function. The calorie-restricted hearts were more elastic and beat in a way that made them resemble the hearts of much younger people - about 15 years younger than their real age. The study isn't conclusive. Differences in the nutritional quality might account for part of the difference in heart health. But the results are consistent with animal studies that have shown calorie restriction increases longevity. "I believe the diet has a powerful effect in modulating aging," says study author Luigi Fontana, assistant professor.
No one knows why calorie restrictions affects aging, but it may help the body avoid diseases caused by excess fat. The breakdown of food can lead to potentially toxic particles called free radicals, so cutting calories may curb that process.
Calorie restriction isn't just about eating fewer calories, but overhauling the diet to improve the quality of calories eaten. "It's not eating half a hamburger, half a bag of french fries and half a sugared beverage," notes Dr. Fontana.
He notes that severe calorie restriction isn't practical for most people, such as children and young adults, but everyone can adopt some of the basic principles, such as shunning foods with empty calories.
To learn more, check out http://www.calorierestriction.org, the Web site of the Calorie Restriction Society that offers tips for getting started and even recipes created by group members. Mr. Delaney, the group's president, is also the co-author of "The Longevity Diet."
Robert Cavanaugh, a 57-year-old retired landscaper from Morehead City, N.C., says that since adopting calorie restriction four years ago, he still eats all his favorite foods. Although he initially measured his food, now he knows intuitively how much to eat. A 450-calorie breakfast consists of oatmeal, powdered and regular skim milk, frozen blueberries, sunflower seeds and chopped walnuts. That leaves 1,300 calories for a big dinner of chicken, tomatoes, broccoli, sweet potatoes and other foods he enjoys. Although his 5'9" frame has dropped from 178 pounds to 150, he says he looks healthy, not scrawny.
"Personally I have taken nothing off my plate," says Mr. Cavanaugh. "I'm not a tofu and watercress kind of guy."
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