INTERMITTENT FASTING

In humans, fasting is achieved by ingesting no or minimal amounts of food and caloric beverages for periods that typically range from 12 hours to three weeks.

Many religious groups incorporate periods of fasting into their rituals including Muslims who fast from dawn until dusk during the month of Ramadan, and Christians, Jews, Buddhists and Hindus who traditionally fast on designated days of the week or calendar year.

In many clinics, patients are now monitored by physicians while undergoing water only or very low calorie (less than 200 kcal/day) fasting periods lasting from 1 week or longer for weight management, and for disease prevention and treatment. Fasting is distinct from caloric restriction (CR) in which the daily caloric intake is reduced chronically by 20–40%, but meal frequency is maintained. Starvation is instead a chronic nutritional insufficiency that is commonly used as a substitute for the word fasting,

The science concerning intermittent fasting is preliminary and uncertain due to absence of studies on its long term effects.Preliminary evidence indicates that intermittent fasting may be effective for weight loss, may decrease insulin resistance and fasting insulin, and may improve cardiovascular and metabolic health, although the long term sustainability of these effects has not been studied.

The American Diabetes Association "found limited evidence about the safety and/or effects of intermittent fasting on type 1 diabetes" and preliminary results of weight loss for type 2 diabetes, and so does not recommend any specific dietary pattern for the management of diabetes until more research is done, recommending instead that "health care providers should focus on the key factors that are common among the patterns".

Weight

There is limited evidence that intermittent fasting produces weight loss comparable to a calorie restricted diet. Most studies on intermittent fasting in humans have observed weight loss, ranging from 2.5% to 9.9%. Alternate day fasting does not affect lean body mass, although one review found a small decrease.

Alternate day fasting improves cardiovascular and metabolic biomarkers similarly to a calorie restriction diet in people who are overweight, obese or have a metabolic syndrome.

Intermittent fasting has not yet been studied in children, elderly, or underweight people, and can be harmful in these populations.Intermittent fasting is not recommended for people who are not overweight.The long-term sustainability of intermittent fasting is still unknown.

Other effects

Night-time eating is linked to impaired sleep quality.Periodic fasting may have a minor effect on chronic pain and mood disorders.In preliminary research, intermittent fasting has shown signs of reducing risk factors for certain disorders, including insulin resistance and cardiovascular disease.Intermittent fasting does not affect bone health.