Intermittent fasting (IF) is an umbrella term for various diets that cycle between a period of fasting and non-fasting. Intermittent fasting can be used along with calorie restriction for weight loss
A 2014 review described that studies done in animal models have shown fasting improves indicators of health—blood pressure, insulin sensitivity, and inflammation—likely through adaptive cellular responses to better handle stress. These findings suggest intermittent fasting has the potential to improve health and reduce the risk of chronic diseases; however this has not been reproduced in long-term human studies. The review concluded that intermittent fasting has not been studied in children, the elderly, or the underweight, and could be harmful in this population.
They also suggest that those choosing to fast for periods of time greater than 24 hours should be monitored by a physician, as changes to the gastrointestinal system or circadian rhythm can occur.