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Food for thought for retail dietitians: Your weight management programs may help shoppers do more than slim their waistlines.
You’ve probably read interesting research linking calorie restriction to increased longevity and delayed progression of several age-related diseases in lab animals. Now, a study supported by the National Institutes of Health (NIH) suggests that cutting calories may lower some risk factors for age-related illnesses in humans. The study found that calorie restriction in normal-weight and moderately overweight people modified risk factors for age-related diseases and influenced indicators associated with longer life span, such as blood pressure, cholesterol and insulin resistance.
The study was a two-year randomized controlled trial in 218 young and middle-aged healthy normal-weight and moderately overweight men and women that measured these outcomes in a calorie restriction group, compared with a control group who maintained their regular diets.
The calorie restriction participants were given weight targets of 15.5 percent 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 percent below one’s regular intake at the start of the study. The calorie restriction group lost an average of 10 percent of their body weight in the first year, and maintained this weight over the second year. Though weight loss fell short of the target, it is the largest sustained weight loss reported in any dietary trial in non-obese people. The participants achieved substantially less calorie restriction (12 percent) than the trial’s 25 percent goal, but maintained calorie restriction over the entire two-year period. The control group’s weight and calorie intake remained stable.
The study was designed to test the effects of calorie restriction on resting metabolic rate (after adjusting for weight loss) and body temperature, which are diminished in many lab animal studies and are proposed to contribute to its effects on longevity. However, the study found a temporary effect on resting metabolic rate, which was not significant at the end of the study, and no effect on body temperature.
Although calorie restriction didn’t show the expected metabolic effects, it did significantly lower several predictors of cardiovascular disease compared to the control group, decreasing average blood pressure by 4 percent and total cholesterol by 6 percent. Levels of HDL (“good”) cholesterol increased. Calorie restriction caused a 47 percent reduction in levels of C-reactive protein, an inflammatory factor linked to cardiovascular disease. It also markedly decreased insulin resistance, which is an indicator of diabetes risk. T3, a marker of thyroid hormone activity, decreased in the calorie restriction group by more than 20 percent, while remaining within the normal range. Some studies suggest that lower thyroid activity may be associated with longer life span.
Reference: Ravussin, E., et al., A 2-Year Randomized Controlled Trial of Human Caloric Restriction: Feasibility and Effects on Predictors of Health Span and Longevity. J Gerontol A Biol Sci Med Sci (2015) 70 (9): 1097-1104. Doi: 10.1093/Gerona/glv057