Intermittent Fasting - Pros and Cons

Intermittent fasting is defined as “periods of voluntary abstinence from food and drink”. There are several types of regimens that fall into this diet description, such as complete alternate-day fasting, modified fasting regimens, time-restricted feeding and religious fasting.


Although there are many studies on rodents and mice on intermittent fasting as well as observational studies on humans, there is currently not enough to make recommendations for the public. The findings of a review paper looked into sixteen intervention trials studying the effect of intermittent fasting on human health.

The results of these studies are listed below.

  • Alternate day fasting consists of two days of fasting with no calories consumed. Limited data show the regimen may moderately reduce weight and improve some metabolic parameters. However, it may not be recommended due to reports of extreme hunger.

  • Modified fasting regimens has a schedule of two non-consecutive fasting days with limited calories consumed and five non-fasting days. Limited data displays the regimen may result in weight loss but there were mixed effects on glucose, lipids and inflammatory markers.

  • Time restricted feeding refers to eating only during specific time frames. Mixed results suggest potential benefits of scheduling feeding time during the day for metabolic health, but more data is needed.

  • Religious fasting varies depending on the religion, but observational studies show that Ramadan fasting can result in temporary weight loss and may improve metabolic markers. However, it may not be an effective method of weight loss since the regimen follows the opposite of the human circadian rhythm.

LISA SAYS:

Intermittent fasting is not a magic bullet that will help everyone lose weight, but it is a strategy that may work for some. People that eat mindlessly and snack all day could benefit from the defined eating hours in the time restricted feeding plan. Another benefit of this plan would be shifting calories consumed to daytime hours and restricting late night meals and snacks.

Unfortunately, this regimen can turn into just another diet that is followed for short term weight loss, but it is not sustainable, so the weight comes back. Health and weight loss are not a “one size fits all” approach so I recommend the following to help with your goals.

1. An appointment with a Registered Dietitian Nutritionist

2. Join a Diabetes Prevention Program

3. Weight Watchers


Written by Lisa Gibson, MS, RDN, FAND

RESOURCES: Harris, Leann, et al. "Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis." JBI Evidence Synthesis, vol. 16, no. 2, Feb. 2018, pp. 507-47, doi:10.11124/JBISRIR-2016-003248. Horne, Benjamin D., et al. "Health effects of intermittent fasting: hormesis or harm? A systematic review." The American Journal of Clinical Nutrition, vol. 102, no. 2, Aug. 2015, pp. 464-70, doi: 10.3945/ajcn.115.109553. Patterson R E and Sears D D. 2017. Metabolic Effects of Intermittent fasting. Annual review of nutrition. 37:371-393. Retrieved from www.annualreviews.org Accessed on 5/22/19.
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