In 1934, Prof. Clive McKay made an extraordinary discovery about the effect of caloric restriction on health and longevity. McKay found that rats fed considerably less food lived approximately 40 percent longer. In fact, rats on a low calorie diet displayed a reduced incidence of diabetes, heart disease, cancer and other ailments. Since then, research has been targeting a variety of animals — most interestingly humans.
Prof. David Levitsky, nutritional science, is currently researching caloric restriction, or CR, by surveying people in the Caloric Restriction Society. Members of the group live off of roughly 1250 calories a day, while the U.S. Food and Drug Administration recommends 2000 calories a day. However, human work in CR diets is more speculative, he said. This is due to a number of factors, including genetic variation, environmental effects and the placebo effect.
“Caloric restriction is the hottest area in nutrition today,” Levitsky said. Levitsky said he does not know of any vitamins, supplements or nutritious remedies that explicitly increase life span, but that the most likely is a CR diet.
The McKay trial has been replicated thousands of times, showing a significant correlation between calorie intake and lifespan in rats. In a study conducted at Washington University of St. Louis, a small group rats were fed 15-25 percent less and had lower cholesterol, blood pressure and greater heart efficiency when compared to the control group. “Restricting calories profoundly delays processes such as cancer and heart disease in several animals, both of which are top causes of human death,” Levitsky said of the study.
“The motive for following CR diets is to sustain a healthy life,” Levitsky said, “and not to stay thin.”
One difficulty, according to Levitsky, is that dieters feel unhappy with a reduced quantity of food. “In today’s society, we are programmed to eat food and it is so readily available that following a CR diet may be difficult,” he said. Eating to capacity causes a deleterious enzymatic reaction in the stomach that contributes to inflammation and dysfunction in the kidneys, possibly leading to further health risks, he added.
This suggests that eating smaller portions not only reduces food waste, but is also healthier in the long run. So why does overeating persist?
As a member of the Cornell Dining Committee, Levitsky said it costs the University more to serve smaller portions in the dining halls. “The time productioncosts of making smaller servings make it cost effective to make larger servings,” he explained.
Therefore, with the current dining hall procedures it is up to students, faculty and guests to decide how much to eat.
Unhealthy fad diets often depict a single dietary component as the nemesis of human health. One of the most popular of these, the Atkins diet, has had high-profile critics that include the president of the American College of Nutrition, the chair of Harvard’s nutrition department and the American Cancer Society.
While it is possible to view to the CR diet as similarly reductionist, the fundamental difference between the Atkins CR is that one promotes curbing calories while the other promotes consuming more. Dr. Atkins’ Diet Revolution: The High Calorie Way to Stay Thin Forever, published in 1989, contradicts the CR diet by advocating for a higher calorie intake.
The Atkins diet was based on data from clinical trials that showed weight loss on the diet. From a macro nutritional scope, however, such data is less clear — test subjects lost weight under a CR diet as well. The real question is which diet consistently and effectively promotes health for each unique individual.
There are many questions with respect to CR diets that remain unanswered. Scientists are still unsure what the expected return in lifespan may be from following a CR diet. More interestingly, the processes at the microscopic level are also unclear.
In light of the hundreds of diets out in the market, the results of studies done at Cornell and other institutions in the future could one day drastically decrease illness, increase longevity and achieve a breakthrough in human biochemical and nutritional understanding, but new experiments and studies are needed.