Health & Wellness

Is a low-calorie diet the secret to longevity?

We all know that cutting back on calories promotes weight loss, but does it also promote longevity? Several thousand Americans seem to think so. Their beliefs are based on animal studies, such as those involving rodents and monkeys, done as far back as the 1930s. The experiments show that eating 25 to 40 percent fewer calories every day can extend animals’ lifespan by up to 50 percent. The idea of living longer depending on what you eat, or don’t eat, is an exciting one, so I wanted to share what we know about this diet.

What is a restricted-calorie diet?
The restricted-calorie diet limits the total calories a person consumes, while retaining a balance of nutrients, in the belief that that will slow down the aging process and reduce the risk of developing diseases associated with aging. This diet, which takes a lot of focus and discipline, is not a weight-loss plan, although, of course, that is one of its side effects.While considered by some to be “extreme,” people who follow a restricted-calorie diet don’t have eating disorders. They eat a balance of nutrient-rich foods and don’t restrict specific foods. While skipping meals is not unheard of as part of a restricted-calorie diet, extended fasting and irregular eating habits that is common with people who have eating disorders are not.

How many calories do you have to cut?
Calories are typically cut anywhere from 25 percent up to 40 percent. The founder of the movement, the late Dr. Roy Walford, advocated reducing daily calories over time to achieve a target body weight that is somewhere between 10 and 25 percent less than your weight when you were in your late teens or early 20s (assuming that you were not overweight or obese at that age). Dr. Walford thought that this would be a healthy adult weight, since it’s before most people assume a more sedentary lifestyle and their metabolic rates start to slow down.

Confused? Let’s do the math. If you’re a 5’ 5” woman weighing 145 pounds, that puts your BMI at 24, which is considered to be healthy by the latest U.S. health standards. To maintain that weight, you need to eat around 2,200 calories a day. If you switch to a restricted-calorie plan, you’re looking at about 1,600 calories a day. The assumption is these calories will include foods that have maximum nutritional power, ranging from protein, to fat, to vitamins and minerals.

It’s pretty easy to get an idea of how much you can eat if you’re interested in this diet. Here’s how to calculate your daily calories on the restricted-calorie diet:

  1. Multiply your present weight by 15. This gives you a reasonable idea of the total number of calories you need to maintain your present weight.
  2. Now divide this number by four. This is the number of calories you need to cut out every day to comply with the restricted-calorie plan.

Does the diet work?
Many studies done on laboratory animals document that daily, extreme calorie restriction is associated with increases in longevity of up to 50 percent. Moreover, the aging process appears to “slow down” and restricted-calorie animals look and act much younger than their control partners of similar ages. Some biological markers, including cholesterol, blood pressure, and blood glucose, have also been found to be much lower in the restricted-calorie group. The lower weight that results from a restricted-calorie diet has a positive effect on the body’s joints and certainly the liver and pancreas have an easier time maintaining body function. (Both organs work overtime when you’re heavier.)

There is no evidence in humans that the length of a healthy life is increased by a restricted-calorie diet. However, many followers of the plan report improved health and a sense of well being with such restricted eating. It is difficult, though, to separate the effects of weight loss from those of eating fewer calories on our bodies. Also there is some evidence that dropping to an “underweight” category, which many restricted-calorie participants fall into, can put people at greater risk of illness. So, the final word is not yet in on restricted-calorie diets and human longevity.

How does it work?
Studies of the anti-aging effects of this diet are still in its infancy, and many of the reasons for why the restricted-calorie diet works are based on theories rather than on scientific fact. New medical findings are only made after years of scientific study. Many followers of the restricted-calorie diet are presently in controlled laboratory studies to look at the effects of this plan on their overall health.

While there have been numerous biological theories, based on the most recent laboratory studies, it seems that the restricted-calorie diet affects the most basic level of cell function. It somehow blocks the enzymes that enhance cell death during metabolic stress, resulting in a more vital, healthier animal. In fact, an antioxidant found in red wine, resveratrol, appears to provide the same biological function in preventing cell death. Further research should shed more information on the possible mechanisms behind the low-calorie diet’s effects.

Can this diet damage your health?
You should always check with your doctor before undertaking any change in your regular diet. With such a reduction in daily calories, there can be a risk of deficiencies when on the restricted-calorie diet, including protein malnutrition as well as low vitamin and mineral levels. It’s important to point out, though, that healthy followers of the restricted-calorie plan pay extreme attention to meeting their daily nutritional needs, which is a must to avoid health problems. Also, protein needs must be met to promote muscle repair and rebuilding, particularly since moderate exercise is an important part of any healthy lifestyle plan.

Dr. Fernstrom’s Bottom Line: For those who follow a restricted-calorie diet, they attribute it to improving their sense of well being. While we have ample evidence of this phenomenon in laboratory animals, the several thousand followers of this plan in the U.S. are an experiment in progress. For most people, a more modest reduction in their daily calories and weight may also provide a healthy outcome and improve longevity.

Madelyn Fernstrom, Ph.D., CNS,is the founder and director of the An associate professor of psychiatry, epidemiology, and surgery at the University of Pittsburgh School of Medicine, Fernstrom is also a board-certified nutrition specialist from theAmerican College of Nutrition.

PLEASE NOTE: The information in this column should not be construed as providing specific medical advice, but rather to offer readers information to better understand their lives and health. It is not intended to provide an alternative to professional treatment or to replace the services of a physician.