A new National Institutes of Health study suggests that cutting calories could help prevent some age-related diseases.
The two-year clinical trial showed that calorie restriction in normal-weight and moderately overweight people did not have some of the metabolic effects seen in earlier animal models, but did influence risk of some degenerative diseases and other factors linked to longevity including blood pressure and cholesterol, the National Institute on Aging reported. The randomized trial, dubbed Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE), was designed to test the effects of calorie restriction on resting metabolic rate and body temperature.
"The study found that this calorie restriction intervention did not produce significant effects on the pre-specified primary metabolic endpoints, but it did modify several risk factors for age-related diseases. It is encouraging to find positive effects when we test interventions that might affect diseases and declines associated with advancing age," said NIA Director Richard J. Hodes. "However, we need to learn much more about the health consequences of this type of intervention in healthy people before considering dietary recommendations. In the meantime, we do know that exercise and maintaining a healthy weight and diet can contribute to healthy aging."
In the study, 218 young and middle-aged healthy normal-weight and moderately overweight men and women were split into a calorie restriction group and a control group. The low-calorie group was given a goal of a 15.5 percent weight loss in the first year, and sustained weight in the second. The participants were instructed to consume 25 percent fewer calories than their normal diet. Overall, the patients achieved an average of 10 percent weight loss over the first year and sustained weight over the second, but only cut their calories by about 12 percent.
The findings revealed that although the metabolic effects from calorie restriction seen in past animal models was not present, several advantages did exist. The diet changes decreased the participants' average blood pressure by four percent and total cholesterol by six percent. It caused a 47 percent reduction in levels of C-reactive protein, which is an inflammatory factor linked to heart disease. The calorie restriction also decreased risk of insulin resistance, and the marker of thyroid hormone activity T3. The researchers noted a few patients developed anemia and saw bone density loss.
"The CALERIE results are quite intriguing. They show that this degree of sustained calorie restriction can influence disease risk factors and possible predictors of longevity in healthy, non-obese people. It will be important to learn how calorie restriction at this level affects these factors despite the lack of the predicted metabolic effects," said Evan Hadley, director of NIA's Division of Geriatrics and Clinical Gerontology and an author of the paper. "Since this group already had low risk factor levels at the start of the study, it's important to find out whether these further reductions would yield additional long-term benefits. It also would be useful to discover if calorie restriction over longer periods has additional effects on predictors of health in old age, and compare its effects with exercise-induced weight loss."
The findings were published in a recent edition of the Journal of Gerontology: Medical Sciences.
