11/01/2022
Evidence from decades of animal and human research points to wide-ranging health benefits of intermittent fasting, according to an NIA-conducted review of the research, published in the New England Journal of Medicine. Still, more research is needed to determine whether intermittent fasting yields benefits or is even feasible for humans when practiced over the long term, such as for years.
Intermittent fasting is an eating pattern that includes hours or days of no or minimal food consumption without deprivation of essential nutrients. Commonly studied regimens include alternate day fasting, 5:2 intermittent fasting (fasting two days each week), and daily time-restricted feeding (such as eating only during a six-hour window).
Hundreds of animal studies and scores of human clinical trials have shown that intermittent fasting can lead to improvements in health conditions such as obesity, diabetes, cardiovascular disease, cancers and neurological disorders. The evidence is less clear for lifespan effects. Animal studies have shown mixed results, with s*x, food composition, age and genetics among the factors that influence longevity. Human trials have mainly involved relatively short-term interventions and so have not provided evidence of long-term health effects, including effects on lifespan.
Although intermittent fasting often results in reduced calorie consumption, weight loss is not the main driver of the health benefits observed in preclinical and clinical studies. Rather, the key mechanism is metabolic switching, in which fasting triggers the body to switch its source of energy from glucose stored in the liver to ketones, which are stored in fat.
“Ketone bodies are not just fuel used during periods of fasting,” “They are potent signaling molecules with major effects on cell and organ functions.”
Ketogenesis, or the increase of ketones in the bloodstream, initiates activity in a variety of cellular signaling pathways known to influence health and aging. This activity enhances the body’s defenses against oxidative and metabolic stress and initiates the removal or repair of damaged molecules. The impact of ketogenesis carries over into the non-fasting period and can improve glucose regulation, increase stress resistance and suppress inflammation.
“Repeated exposure to fasting periods results in lasting adaptive responses that confer resistance to subsequent challenges,” The “broad-spectrum benefits” include not only disease resistance but also improved mental and physical performance.