Intermittent fasting (IF) is an umbrella term for forms of fasting that cycle between periods of fasting and feeding. Fasting has dated back thousands of years and been a part of religious tradition for groups including Christians, Hindus, Jews, Muslims, and Buddhists. Some of the beneficial effects of fasting have been known to kick in starting in as little as 12 hours into a fasted state, and it is suggested that the effects grow more with more extended periods of fasting.
While caloric restriction may be psychologically difficult for some individuals, there is an growing body of scientific research showing health benefits including longevity, improved metabolic state, improved insulin resistance, and cognitive improvement. Studies on intermittent fasting have been performed in both animals and humans.
In experiments with yeast and rodents, lifespan is increased by caloric restriction. In rhesus monkeys, diabetes, cancer, and cardiovascular disease can be ameliorated by caloric restriction. Humans with mutations in the growth hormone receptor and nutrient sensing pathways also tend to have longer life spans, as well as huge reductions in pro-aging molecular signaling, cancer, and diabetes.1Mutations or inhibition of molecular pathways associated with nutrient sensing can mimic this enhancement of lifespan. This evidence points to a variety of effects of modulation of human biology through nutrient sensing pathways - with intermittent fasting being a powerful mechanism to regulate these pathways.
Figure 1. Intermittent fasting affects multiple organ systems. In the brain, the hippocampus, striatum, hypothalamus, and brainstem are affected. IF enhances parasympathetic neural activity in the gut, heart and arteries. IF depletes glycogen reserves in the liver, increasing breakdown of fats. And IF increases insulin sensitivity in muscle and liver cells - insensitivity to insulin in THE major defect in type II diabetes.
Intermittent fasting can promote increased neuron production, called neurogenesis, and increases the production of signaling molecules that promote neural health and function - such as brain derived neurotrophic factor (BDNF), glutamate, insulin, and GLP-1. IF can also exert neuroprotective and mood elevating effects. (Learn more)
Research has suggested that intermittent fasting may have a positive effect on longevity. The research ranges from retrospective studies on human populations with high longevity to prospective studies involving biomarker analysis before and after periods of fasting or caloric restriction. (Learn more)
Research has suggested that intermittent fasting may have a positive effect on metabolism. The research ranges from animal studies on insulin resistance and obesity biomarkers to prospective human studies involving biomarker analysis before and after periods of fasting or caloric restriction. (Learn more)
Research has suggested that intermittent fasting may have a positive effect on immunity and inflammation. This area has been studied in animals and humans with respective to relevant biomarkers. (Learn more)
There is very little concomitant research about the specific effects of intermittent fasting in women. Intermittent fasting represents a significant lifestyle shift for most people, but women face additional challenges including metabolic balance, maintaining periods, sleep, and eating disorders. (Learn more)
We suggest reading our guide, engaging in online discussion on our forum, and joining the WeFast Intermittent Fasting Slack group.
Read our Intermittent-fasting starter guide
Guevara-Aguirre, J., Balasubramanian, P., Guevara-Aguirre, M., Wei, M., Madia, F., Cheng, C. W., ... & de Cabo, R. (2011). Growth hormone receptor deficiency is associated with a major reduction in pro-aging signaling, cancer, and diabetes in humans. Science translational medicine, 3(70), 70ra13-70ra13.