Fasting Diets

  • Author: Jennifer Warner
  • Medical Editor: Charles Patrick Davis, MD, PhD
    Charles Patrick Davis, MD, PhD

    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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What are the health risks of fasting diets?

Although more research is needed to fully understand the long-term benefits and risks of fasting diets, Lemond says there are also short-term risks to consider. "There is an immediate side effect of irritability and fatigue that can't be underestimated," said Lemond. In addition, Lemond says fasting for more than three days can impair immune system function and make you more vulnerable to infection and illness.

Anyone considering a fasting or detox diet should first consult with a health care professional, and certain people should never try one of these diets. For example, Lemond says fasting diets are not recommended for people with diabetes because such an extreme diet can interfere with blood sugar control. Also, fasting or any other type of diet that severely restricts calories is not recommended for pregnant or women who are breastfeeding. People with other medical problems and anyone who takes medicine need to be careful because many medications are recommended to be taken at certain times either with or without foods; checking with your doctor(s) that prescribe your medications before you begin any major diet change is strongly advised.

Medically reviewed by Joseph Palermo, DO; American Osteopathic Board Certified Internal Medicine


Angela Lemond, RDN, CSP, LD, Spokesperson for the Academy of Nutrition and Dietetics, Plano, Texas.

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Medically Reviewed by a Doctor on 4/7/2015

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