Calorie restriction is defined as a reduction of 30-60% of one’s regular calorie intake while maintaining a diet that provides enough nutrients to prevent malnutrition.
Calorie restriction stimulates a defensive state designed to help an organism survive environmental and metabolic adversity. This non-genetic strategy has been observed to encourage youthfulness and extend average and maximum lifespan in most living creatures.
Centenarians from Okinawa
Probably the most intriguing epidemiological evidence supporting the role of calorie restriction in lifespan extension in humans comes from the Okinawans. Compared to most industrialized countries, Okinawa, Japan, has 4–5 times the average number of centenarians with an estimated 50 in every 100,000 people. Both the average and maximum lifespan are increased in Okinawans. From age 65, the expected lifespan in Okinawa is 24.1 years for women and 18.5 years for men compared to 19.3 years for women and 16.2 years for men in the United States.
What is interesting about this population is that a low caloric intake was reported in school children on the island more than 40 years ago and later studies confirmed a 20% calorie restriction in adults residing on Okinawa compared to mainland Japan.
A recent estimate of the energy balance of a cohort of Okinawa septuagenarians during youth to middle age suggested a 10%–15% energy deficit. This energy deficit can be attributed to laborious occupations and daily activities as farmers and a diet that was rich in nutrients yet low in energy density.
Why Caloric Restriction?
Many inpiduals choose to pursue the approach of calorie restriction for its supposed anti-aging effects. Calorie restriction has been shown to extend longevity in animal models via a number of proposed metabolic avenues. Whether it’s activating sirtuin production, protecting telomere length, or reducing oxidative stress, safe calorie restriction with optimal nutrition (CRON) may be a helpful way to support a healthy aging process. Calorie restriction is by no means the end all and be all of longevity, but it is a good first start that is free to try.
Members of the sirtuin family of NAD(+)-dependent protein deacetylases are important regulators of longevity in yeast, worms, and flies. Mammals have seven sirtuins (SIRT1-7), each characterized by differences in subcellular localization, substrate preference, and biological function. While it is unclear whether sirtuins regulate aging in mammals, it is clear that sirtuins influence perse aspects of their metabolism. Indeed, SIRT1 promotes oxidation of fatty acids in liver and skeletal muscle, cholesterol metabolism in liver, and lipid mobilization in white adipose tissue. Moreover, small-molecule activators of SIRT1 have recently been shown to protect mice from the negative effects of a high-fat diet.
Sirtuins, proteins that regulate many biological pathways, are activated during calorie restriction, and studies show that these proteins may extend lifespan. Whatever the mechanism, it does reduce the body’s production of reactive oxygen species (ROS) which reduces damage to DNA. Sirtuins might provide important new targets for the treatment of obesity and related diseases. Caloric restriction lowers metabolism, decreasing the oxidation often associated with metabolic processes.
Effects on The Thymus
The thymus, is situated in the chest, just above the heart, is part of the immune system. The thymus produces T cells — white blood cells that are essential for fighting infections. Hormones released by the thymus inhibit the aging process. As people age, their thymus becomes fatty and smaller, and it produces fewer T cells. Older people are more susceptible to infections because of this reduced immunity. Those with calorie-restricted diets had greater functional thymus volume than those with unchanged diets. The thymus glands of the restricted diet people are less fatty and produced more T cells than those of the unrestricted diet.
Calorie Restriction Leads to Telomere Maintenance
Telomeres are distinctive structures found at the ends of our chromosomes. They consist of the same short DNA sequence repeated over and over again. Telomeres are often compared to the plastic caps at the end of a shoelace, and in this analogy, the shoelace itself would represent a set of your DNA strands. The telomere keeps the strands of DNA from fraying and coming apart. Without telomeres, important DNA would be lost every time a cell pides (usually about 50 to 70 times).
Over time (and also due to various lifestyle factors), the telomere degrades and shortens, which contributes to aging.
Age-related decline in immunity is characterized by stem cell telomere shortening, and disruption of cell-to-cell communication, leading to increased patient risk of disease.
Shortening telomeres is prone to heart disease and infectious diseases, which is life-threatening. Populations with short telomere of somatic cells are reported to have shorter life expectancy than those with long telomere. Recent data have demonstrated that chronic inflammation exerts a strong influence on immune aging and is closely correlated with telomere length in a range of major pathologies. The immune system is highly sensitive to shortening of telomeres as its competence depends strictly on cell renewal.
Dietary restrictions and daily exercise are important to stop the acceleration of telomere shortening. Furthermore, it is highly desirable to initiate treatment of metabolic disorders early.
Caloric Restriction Decreases Risk of Heart Disease
Two of the major risk factors for cardiovascular disease (CVD) are advancing age and obesity. An intervention able to positively impact both aging and obesity, such as caloric restriction may prove extremely useful in the fight against CVD.
Eat Less, Live Longer
Caloric restriction is the only lifestyle intervention that has repeatedly been shown to increase maximum life span and to retard aging in laboratory rodents.
Caloric restriction shows positive effects on many of the causes associated with heart disease. Studies have found it helps protect against obesity and hypertension, health conditions that greatly influence heart disease risk.
Adiponectin, a hormone (that its production increases under caloric restriction) promotes cardiovascular and metabolic health. Adipocytes, also known as lipocytes and fat cells, are the cells that primarily compose adipose tissue, specialized in storing energy as fat. Adiponectin is the most abundant peptide secreted by adipocytes, whose reduction plays a central role in obesity-related diseases, including insulin resistance/type 2 diabetes and cardiovascular disease. In addition to adipocytes, other cell types, such as skeletal and cardiac myocytes and endothelial cells, can also produce this adipocytokine.
Adiponectin has direct actions in liver, skeletal muscle, and the vasculature. Adiponectin exists in the circulation as varying molecular weight forms, produced by multimerization. Studies have shown that adiponectin administration in humans and rodents has insulin-sensitizing, anti-atherogenic, and anti-inflammatory effects, and, in certain settings, also decreases body weight.
Caloric restriction increases adiponectin expression by adipose tissue and prevents the inhibitory effect of insulin on circulating adiponectin in rats. Aging is associated with redistribution of body fat and the development of insulin resistance. White adipose tissue emerges as an important organ in controlling life span. Caloric restriction delays the rate of aging possibly modulated partly by altering the amount and function of adipose tissue.
Only a subset of heart disease patients should consider calorie restriction alongside professional medical advice.
Encourages Weight Loss
A study of overweight, postmenopausal women found all participants experienced significant decreases in body weight and body mass index following a calorie restricted meal plan. Some participants experienced better blood sugar management as a result of the caloric restricted diet. While this may be good news for type II diabetics, those suffering from blood sugar issues should make sure they are receiving the proper nutrients that further stabilize blood sugar spikes.
Promotes Healthy Cellular Function
Calorie restriction decreases insulin levels and stimulates cell repair.
Inpiduals who practice long-term caloric restriction for the purpose of supporting health and longevity have shown a lower risk of cellular dysfunction. Laboratory studies of animals, including rats, fruit flies, worms, and mice, show that those fed a calorie-restricted diet may live up to twice as long as those with an unrestricted diet.
Unlike many weight loss diets, a calorie-restricted diet involves small reductions of habitual calorie intake over a long period. People usually lose some weight, but this is not the main aim of calorie restriction.