What is intermittent fasting? Does it have health benefits?
Answer From Manpreet Mundi, M.D.
Intermittent fasting means that you don't eat for a period of time each day or week. Some popular approaches to intermittent fasting include:
- Alternate-day fasting. Eat a normal diet one day and either completely fast or have one small meal (less than 500 calories) the next day.
- 5:2 fasting. Eat a normal diet five days a week and fast two days a week.
- Daily time-restricted fasting. Eat normally but only within an eight-hour window each day. For example, skip breakfast but eat lunch around noon and dinner by 8 p.m.
Some studies suggest that alternate-day fasting is about as effective as a typical low-calorie diet for weight loss. That seems reasonable because reducing the number of calories you eat should help you lose weight.
Can intermittent fasting improve your health? Losing weight and being physically active help lower your risk of obesity-related diseases, such as diabetes, sleep apnea and some types of cancer. For these diseases, intermittent fasting seems to be about as beneficial as any other type of diet that reduces overall calories.
Some research suggests that intermittent fasting may be more beneficial than other diets for reducing inflammation and improving conditions associated with inflammation, such as:
- Alzheimer's disease
- Multiple sclerosis
It's important to note that intermittent fasting can have unpleasant side effects, but they usually go away within a month. Side effects may include:
Intermittent fasting is safe for many people, but it's not for everyone. Skipping meals may not be the best way to manage your weight if you're pregnant or breast-feeding. If you have kidney stones, gastroesophageal reflux, diabetes or other medical problems, talk with your doctor before starting intermittent fasting.
April 21, 2020
Manpreet Mundi, M.D.
See more Expert Answers
- de Cabo R, et al. Effects of intermittent fasting on health, aging, and disease. New England Journal of Medicine. 2019; doi:10.1056/NEJMra1905136.
- Patterson RE, et al. Metabolic effects of intermittent fasting. Annual Review of Nutrition. 2017; doi:10.1146/annurev-nutr-071816-064634.
- Cioffi I, et al. Intermittent versus continuous energy restriction on weight loss and cardiometabolic outcomes: A systematic review and meta-analysis of randomized controlled trials. Journal of Translational Medicine. 2018; doi:10.1186/s12967-018-1748-4.
- Mattson MP, et al. Impact of intermittent fasting on health and disease processes. Ageing Research Reviews. 2017; doi:10.1016/j.arr.2016.10.005.
- Rakel D, ed. Alzheimer disease. In: Integrative Medicine. 4th ed. Elsevier; 2018. https://www.clinicalkey.com. Accessed April 6, 2020.
- Phillips MCL. Fasting as a therapy in neurological disease. Nutrients. 2019; doi:10.3390/nu11102501.
- Gordon B. What is intermittent fasting? Academy of Nutrition and Dietetics. https://www.eatright.org/health/weight-loss/fad-diets/what-is-intermittent-fasting. Accessed April 12, 2020.