Historically, there is a long religious tradition of periodic reduction of calorie intake. In yoga many practices require a reduction of calories, avoidance of certain foods, or fasting. Research studies on calorie reduction (CR) and intermittent fasting (IF) suggest that there are numerous benefits to these traditions, particularly in reducing oxidative damage and aging of the brain.
However, readers must be cautioned that before undertaking anything it is imperative to seek professional medical advice. The studies indicate promise in animals but sufficient data has not been compiled for humans.
- What is a fast?
Growing up in India, fasting was something almost all adults did. The word has different meanings and people made their own variations. The Hindu fast allows tea, coffee, milk, or juice once or twice a day. Some fruit maybe fine perhaps as a meal, or tapioca, or potatoes. Some do a salt-free, grain-free fast. A dinner is permissible. And some fast on Mondays, some Tuesdays, some Saturdays. There is the Muslim Ramadan when no food or water is allowed from sunrise to sunset for 30 days. The Jain fast permits no food for about 36 hours, nothing but water. Those who cannot do that, especially during the eight days of Paryushan, may eat just one simple meal, usually lunch, and only water is allowed during the day–no fruit, tea, coffee, milk, juice. During Lent, many give up a favorite food item and on Fridays they may not eat meat.
- What is calorie restriction?
Calorie restriction is defined as undernutrition without malnutrition. In experimental studies, this means reducing animal diets by a certain percent of calories as compared to ad libitum but keeping the diet approximately unchanged in total protein, vitamins, and minerals.
Source: Nutritional Modulation of Aging: Effect of Caloric Restriction
Some studies state calorie restriction to be a reduction of 25 to 30 percent.
- What is intermittent fasting?
Generally, this means fasting for 24 hours–water and low-calorie fluids are allowed–followed by normal eating for the next 24 hours. This is alternate day fasting. There are some suggestions that this type of fasting has the same effect as calorie restriction.
- Nongenetic Calorie Restriction Increases Lifespan
Age-related accumulation of cellular damage and death has been linked to oxidative stress. Calorie restriction (CR) is the most robust, nongenetic intervention that increases lifespan and reduces the rate of aging in a variety of species. Mechanisms responsible for the antiaging effects of CR remain uncertain, but reduction of oxidative stress within mitochondria remains a major focus of research.
Source: Caloric restriction induces mitochondrial biogenesis and bioenergetic efficiency
- Calorie Reduction Effect on Blood Pressure, Stroke, and Insulin
Intermittent fasting Intermittent fasting (IF; reduced meal frequency) and caloric restriction (CR) extend lifespan and increase resistance to age-related diseases in rodents and monkeys and improve the health of overweight humans. Both IF and CR enhance cardiovascular and brain functions and improve several risk factors for coronary artery disease and stroke including a reduction in blood pressure and increased insulin sensitivity.
- Life-span and health-span extension by caloric restriction and intermittent fasting
Health-span is the time of our lives that are free of disease. Caloric restriction and intermittent fasting “are the most effective way of extending the life-span of mammals without genetically altering them.” They also indicate beneficial health effects.
Source: Life-span and health-span extension by caloric restriction and intermittent fasting
- Caution
The above source, a National Institute of Health study, also makes it clear that this is a complex subject with no clear answers–there is still much to learn about aging. The article states that to date, there are no well-controlled studies to determine the long-term effects of CR and IF on humans. A 30 percent calorie reduction in rhesus monkeys, so far, looks promising.
The most beneficial effects of IF and CR that have been noted have been in overweight or obese animals. Results are unclear for animals with a healthy weight who exercise and also have some form of mental stimulation.
Females in particular must be cautious of excessive loss of body fat which can lead to menstrual irregularities, amenorrhea (absence of periods), bone thinning, and osteoporosis.
Mahasri Yoga 
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