By Suzanne Dixon, MPH, MS, RD
Healthnotes Newswire (August 13, 2009)—Caloric restriction is the practice of limiting calorie intake without causing malnutrition, with the goal of improving health and slowing the aging process. It is the only health intervention consistently shown to improve length of life in all species studied—until recently, however, primates, including humans, were rarely studied. Recently released results of a 20-year, controlled, calorie-restricted trial in 76 rhesus monkeys have filled in that knowledge gap.
A typical calorie-restricted diet reduces intake by about 30% of what is calculated to maintain a healthy body weight for an individual. For example, if a healthy, moderately active adult requires 2,200 calories to maintain his or her weight, a calorie-restricted diet would have this person eating about 1,540 calories per day.
For this research, the monkeys were randomly selected for the normal diet group (control) or the calorie-restricted group. In the restricted group, each monkey’s diet was individually designed to reduce calories by 30%, based on baseline food intake, body weight, and age.
After 20 years, the study yielded the following results:
• 37% of the control monkeys and 13% of the calorie-restricted monkeys died of age-related causes, including diabetes, cancer, and cardiovascular disease.
• Body weight in the calorie-restricted group was reduced and weight loss predominantly was due to loss of fat mass.
• The calorie-restricted monkeys experienced less age-related loss of muscle mass.
• 42% of the control group animals developed prediabetes or diabetes, while none of the calorie-restricted monkeys developed these conditions.
• The occurrence of cancer and cardiovascular disease were reduced by 50% each in the calorie-restricted group compared with the control group.
• The calorie-restricted monkeys lost less gray matter, a type of tissue in the brain, compared with the control group.
The key to healthy calorie-restricted is that the diet focus on nutrient-rich foods such as vegetables, fruit, whole grains, and legumes (beans and peas). With about 1,500 calories per day, there isn’t much room for potato chips and cake! This type of diet is very hard to follow consistently. Furthermore, people who do follow a well-balanced calorie-restricted diet note that they are hungry…all the time.
The take-home message is that it isn’t realistic or practical for everyone to follow a calorie-restricted diet. Especially because of the high risk of malnutrition if this type of diet isn’t carefully planned and implemented. It’s tough to get all of the nutrients needed for good health in such a small number of calories. Note that calorie restriction is never an option for children, as it can stunt growth.
So, what is practical? Very few among us could pull off a calorie-restricted diet for any length of time, but it is within our means to eat more fruits, vegetables, and whole grains; reduce intake of sugars and fats; exercise regularly; and maintain a healthy body weight. Regardless of whether calorie restriction can prolong human life and enhance health, we do know that obesity, poor diet, and lack of exercise shorten life and lead to chronic disease, poor health, and suffering.
Suzanne Dixon, MPH, MS, RD, an author, speaker, and internationally recognized expert in chronic disease prevention, epidemiology, and nutrition, has taught medical, nursing, public health, and alternative medicine coursework. She has delivered over 150 invited lectures to health professionals and consumers and is the creator of a nutrition website acclaimed by the New York Times and Time magazine. Suzanne received her training in epidemiology and nutrition at the University of Michigan, School of Public Health at Ann Arbor.
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