The concept of Intermittent Fasting seems to be the latest diet fad fueled mostly by laboratory rather than human studies. Investigations suggest an excess of energy intake especially during early and mid-life may be associated with increased mortality. For over 100 years laboratory studies in a wide variety of animal models consistently demonstrate caloric restriction often leads to a dramatic increase in lifespan. The average dietary intake is restricted to about 40% of normal.

Amazingly this added longevity may be accomplished without a total decrease in energy intake. Rather manipulation of meal frequency and meal size may be the key issues with significant inter-individual variation regarding benefits.

Intermittent Fasting fits into the overall category of caloric restriction. Included among the options are calorie restricted eating. Generally this means fasting for 12-20 hours a day and consuming relatively few calories on those days. A popular variant is Intermittent Fasting for 2 days out of the week. Either a complete fast or consuming fewer than 25% of typical calories will suffice. Alternate day fasting is yet another option. Another choice is restricting calories to no more than 30% of normal for 5 consecutive days during the month and repeating the diet 3-4 times each year.

In laboratory investigations these dietary manipulations lower the glucose, insulin and certain growth factors while simultaneously increasing production of ketone bodies in the liver and intestine. Caloric restriction protects against obesity, cardiovascular disease, high blood pressure, diabetes, degeneration of the central nervous system and reduces the incidence of cancer. Animals show improved balance and coordination as well as greater endurance on physical activities such as running.

Caloric restriction in animals improves recovery after surgery, improves mental health and reduces clinical manifestations after spinal cord damage and traumatic brain injury. It decreases age related eye disease and preserves hearing into old age. It may lessen symptoms akin to multiple sclerosis and improves both short term and long term memory.

The mechanisms associated with improved health from caloric restriction are still in their infancy but appear to involve the circadian clock, ketone bodies and their effect on metabolism and even an altered gut microbiome.