Calorie Restriction Modifies Risk Factors for Age-Related Diseases

Results of a 2-year-long human study of calorie restriction produced mixed results. The randomized-controlled Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE) study investigated the effects of calorie restriction on young and middle-aged healthy normal-weight and moderately overweight men and women. Participants in the calorie restriction group were given weight targets of 15.5% weight loss in the first year, followed by weight stability over the second year. This target was the weight loss expected to be achieved by reducing calorie intake by 25%. In actuality, the group achieved substantially less calorie restriction (12 %) than the trial goal; however calorie restriction was maintained over the entire 2-year period. Participants in the control group were asked to maintain their normal diet throughout the study. The study was designed to test the effects of calorie restriction on resting metabolic rate and body temperature. Both of which have been seen to drop in animal studies, and are thought to contribute to calorie restriction’s effects on longevity. Results showed that calorie restriction had a temporary effect on resting metabolic rate, although this was not significant at the end of the study. No effect on body temperature was seen. However, results did show that calorie restriction modified some risk factors for age-related diseases and influenced indicators associated with longer life span. Calorie restriction significantly lowered several cardiovascular risk factors compared to the control group – average blood pressure fell by 4%, total cholesterol dropped 6%, and levels of HDL cholesterol increased. Levels of the inflammatory marker C-reactive protein fell by 47%. Calorie restriction also decreased insulin resistance, an indicator of diabetes risk. Finally, levels of T3, a marker of thyroid hormone activity, dropped by more than 20% in the calorie restriction group. This finding is of particular interest as studies suggest that lower thyroid activity may be associated with a longer life span. “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,” said Evan Hadley, M.D, director of The National Institute on Aging’s Division of Geriatrics and Clinical Gerontology and an author of the paper. “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.”