Back in the 1930s, Dr. Clive McCay was the first to publish data showing that rodents appear to age more slowly and live a lot longer when their food intake was restricted.1 Since McCay?s research in rodents, many other species of animals have been subjected to calorie restriction. In every case, the animals fed 25-40% fewer calories than control animals have been shown to live significantly longer. They also appear to age more slowly.2 The anti-aging impact of reduced calorie intake does not appear to be related to the ratio of carbohydrate, fat and protein in the diet.3 Of course, the amounts and types of fats, proteins and carbohydrates in the diet do impact disease processes like atherosclerosis and coronary heart disease.
Recent studies in dogs and monkeys kept on calorie-restricted diets also show that they appear to age more slowly and experience favorable alterations in biological markers of aging and disease.4 Biological markers for aging that have been shown to improve on calorie-restricted diets include lower body temperature and serum insulin levels. Higher levels of the hormone DHEAS are also associated with slower aging. These same biomarkers of aging in animals have been shown to be associated with increased longevity in men.5While it seems likely that calorie restriction may very well slow the aging process and increase the life span of humans, it is very difficult to restrict calorie intake, as it leaves most people hungry and often obsessed with food. Researchers recently compared various risk factors for atherosclerosis in a group of 18 subjects who are practicing calorie restriction (CR) and age-matched healthy controls. Table 1 shows the average differences in a variety of risk factors for atherosclerosis. The CR subjects had a markedly reduced risk for atherosclerosis. In addition, the researchers also examined the thickness of the carotid arteries, which are the arteries in the neck that supply blood to the brain. They found no evidence of thickening in any of the CR subjects and the walls of their arteries were about 40% less thick than the arteries of the comparison group. While the results of this study do not prove the CR subjects are aging more slowly than the comparison group, the results certainly demonstrate that their risk of dying from cardiovascular disease is markedly lower. The proportion of the improvements seen in these CVD risk factors that was due to CR and how much might have been caused by a lower intake of saturated fat, hydrogenated fat, cholesterol and salt is difficult to say. This is because the published data did not provide quantitative data on the intake of these and other dietary components, like fiber intake, known to impact risk factors for atherosclerosis.6The bottom lineIt is best to eat more high-satiety foods like fruits, grains, beans and whole grains with a high fiber and water content. This is because these foods will provide more satiety per calorie. This allows calorie restriction and loss of body fat while minimizing hunger. The people who were on the CR diet had an average BMI of 19.6 and about 1/7th the abdominal fat of control subjects; see charts below.
By James Kenney, PhD, RD, LD, FACN.References:1. J Nutr 1939;18:1-132. Aging Clin Exp Res 2001;13-2613. J Gerontol Biol Sci 1988;43:59-644. J Nutr 2003;133:2887-925. Science 2002;297:8116. Proc Nat Acad Sci. 2004;10:6659-63
