How can intermittent fasting affect health?

Intermittent fasting may affect several aspects of health, but the benefits are not universal and depend on the person and the eating pattern.

• Metabolic health and weight: Restricting eating to a daily window has been associated with improved insulin sensitivity and liver enzymes; an eight-hour eating window was also reported to produce modest weight loss and lower blood pressure in obese adults. Weight change still depends in part on calories consumed versus burned. 1 2 3
• Cellular repair and gut health: Fasting is described as shifting the body toward cellular repair and clearance, including autophagy. Time-restricted eating has also been linked with changes in gut microbes and may help some people with irritable bowel syndrome or colitis. 4 5
• Possible downsides and uncertainty: Some people may experience poorer mood or hormone effects; one study in elite cyclists found lower free testosterone. Evidence for longer-term benefits in humans is uncertain, and effects observed in animals do not necessarily translate to people. 6 7 8

So fasting may be useful for some health measures, but it is not a guaranteed benefit for everyone. 9