Caloric Restriction: A Lifestyle Intervention With Compelling Cardiovascular Benefits

Cardiovascular disease is the leading cause of death in the United States and is soon becoming the leading cause of death in most countries in the world. In the USA, cardiovascular disease claims more lives each year than cancer, chronic lower respiratory diseases, accidents, and diabetes mellitus combined. The increasing age along with the obesity and diabetes epidemic will continue to keep cardiovascular disease as the number one health problem in the world.

There has been a recent emphasis on lifestyle changes to prevent the development of cardiovascular risk factors. These include cessation of smoking, prevention of obesity, incorporation of a heart friendly diet and implementation of regular exercise program. Caloric restriction is a major lifestyle intervention that is also generating increasing scientific interest as a method of reducing cardiovascular morbidity and mortality.

Caloric restriction is the only lifestyle intervention that has consistently been shown to increase the maximum life span in laboratory mice and rats. It achieves this by retarding the aging processes. These effects have been also seen in yeast, worms, fish, spiders and many other lower order animals. Caloric restriction is achieved by feeding animals 70%-75% as many calories as controls, in a nutritious balanced way, avoiding malnutrition.

Similar data, confirming lifespan extension, is emerging from studies in rhesus monkeys. Rhesus monkey is a nonhuman primate that has close evolutionary relationship to humans. It bears many similarities to humans including anatomy and bodily functions such as physiology, immunology, endocrinology and neurology. The rhesus monkey is also prone to common human diseases such as obesity, metabolic syndrome, diabetes mellitus and cardiovascular pathologies. As a result, there is considerable experimental interest in retarding or reversing the aging processes in these ancestral cousins and its possible applicability in humans.

Studies in the rhesus monkeys show that caloric restriction induces the following positive changes on cardiovascular risk factors:

1.Reduction in weight of about 30% compared to the ad libitum group, mainly due to a decrease in visceral fat.
2. Improved glucose homeostasis as evidenced by improved fasting insulin and glucose levels, improved HbA1c and decreased insulin resistance.
3. Decreased blood pressure and improved lipid parameters.
4. Reduced body temperature more than that explained by the reduction in body mass

Several studies have shown improved cardiovascular morbidity and mortality in humans with calorie restriction. Epidemiological observations from different populations of the world have shown dramatic decreases in cardiovascular diseases, as a result of unintentional caloric restriction. World War II related food shortages in some European countries resulted in a sharp decrease in coronary heart disease mortality, only reversing after the war ended. Japanese living on the Okinawa island, generally eat 30% less calories than the average Japanese population, and experience an almost 35% lower rate of cardiovascular disease and cancer mortality. Similar changes were reported during the food rationing in Cuba due to a significant economic downturn from 1989 to 2000. Deaths caused by diabetes declined by 51%, coronary heart disease mortality dropped 35% and stroke mortality by 20%. Similar effects were noted in the Biosphere experiment. Due to declining food stores, caloric restriction was enforced on the eight individuals, for alamost 2 years. These individuals not only lost weight and fat mass, but also showed improvements in basal glucose, basal insulin, insulin sensitivity, and blood pressure. These effects basically replicated the experimental changes noted in non-human primates.

Reduction of caloric intake by 25%-30% on a consistent basis may be difficult to achieve. Further this reduction has to be nutritionally balanced, with adequate intake of essential macro and micro nutrients. The data on the beneficial cardiovascular effects of caloric restriction, however, are compelling. Calorie restriction may be an important life style intervention to dramatically reduce major cardiovascular risk factors and, and increase healthspan (healthy years) and lifespan in humans.