Young woman tracking intermittent fasting schedule

How long should you do intermittent fasting?

Written on February 3, 2023 by Amy Harris, MS, RN, CNM. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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After hearing so much buzz about intermittent fasting (IF) in the news, in your feeds, or from your friends, did you decide to give this new diet trend a try? Are you now wondering how long should you do intermittent fasting? In this post, learn more about whether intermittent fasting should be a life-long switch or a short-term fix.

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What is intermittent fasting?

Instead of focusing on what you eat like many popular diets, intermittent fasting focuses on when you eat. That's because it is an eating pattern that includes hours or days with no or minimal food consumption (called fasting) interspersed with hours or days when you eat a regular diet [1]. There are several popular variations of intermittent fasting:

  • Alternate day fasting
  • 5:2 intermittent fasting (fasting two days each week)
  • Daily time-restricted feeding (such as eating only during a six-hour window)

Studies indicate that alternate-day fasting is about as effective as a typical low-calorie diet for weight loss [1].

Why do you lose weight when following an intermittent fasting diet plan?

People lose weight on IF diets because they reduce the total calories they take in. However, some overly-restrictive diets that severely limit calories can backfire, causing your body to adapt to the calorie restriction and prevent further weight loss [2]. Intermittent fasting attempts to work around your body’s unhelpful adaptations by cycling in and out of a low-caloric intake level for a brief time, followed by normal eating.

Other people may lose weight following intermittent diet plans because it is easier for them to control when they eat than what they eat [3]. Not everyone loves to count carbs or track their macros on the latest app. Others are happiest following a schedule of timed eating. If this describes you, then you may be more successful at making intermittent fasting a regular habit and not just a short-term diet fix.

Is it healthy to continue intermittent fasting indefinitely?

We think so, but it might be too soon to tell. According to the National Institute on Aging and research published in the New England Journal of Medicine, “decades of animal and human research points to wide-ranging health benefits of intermittent fasting” [4].

Identified benefits of intermittent fasting diets include [5]:

  • Mild to moderate weight loss (1–8% from baseline)
  • Consistent reductions in calorie intake (10–30% from baseline)
  • Decreased blood pressure
  • Decreased insulin resistance
  • Reduced inflammation
  • Reduced oxidative stress

Research shows that these changes can help you live a longer, healthier life [4]. But, unfortunately, we need longer-running studies of people using intermittent fasting diets to say they are safe enough to stay on indefinitely [6].

We know that the most successful diets are those that stop being diets and become the way you eat on the regular. Early studies show that people stick with IF longer than they do with other more restrictive or harder-to-follow diets [3]. So, if people stick with IF longer, they may be more likely to lose weight and keep that weight off. If this is true, it may be healthier for many people to continue with intermittent fasting indefinitely and never stop.

When should you stop intermittent fasting?

There are several specific medical or health circumstances where it could harm your health to continue (or start) intermittent fasting. These include [1,3]:

  • Pregnancy
  • Breastfeeding
  • Type 1 diabetes
  • Gastroesophageal reflux (GERD) or heartburn
  • Kidney stones
  • Children or teens younger than age 18
  • A history of an eating disorder
  • Experiencing unpleasant side effects (hunger, fatigue, nausea, headaches, difficulty sleeping) lasting longer than one month after starting intermittent fasting
  • Diagnosis of a new medical condition

It is always a good idea to review any diets you are following with your healthcare provider whenever you are diagnosed with a new condition or illness or prescribed a new medication.

Stop intermittent fasting when it no longer works for you

The simple answer to the question of how long to do intermittent fasting is that you should stop when it no longer works for you. Examples of such situations could be [6]:

  • Your fasting periods are interfering with your professional life (difficulty concentrating on fasting days or too many work meetings involving meals).
  • You hate skipping meals with family or friends during your fasting times.
  • You have started to regain weight.
  • You began an intense exercise plan, so you need to consume more calories.
  • You haven’t lost any weight after three months of trying intermittent fasting.
  • You find yourself overeating on non-fasting days to compensate for fasting days.

It can be frustrating and disheartening to feel like a diet failure. So rather than giving up altogether, turn to Everlywell for support along your healthy weight journey.

Everlywell can help you stay healthy while intermittently fasting

Whether or not to stop intermittent fasting should be a personalized decision made in consultation with a licensed healthcare provider, nutritionist, or dietitian.

Everlywell’s telehealth offering includes weight management consultation services, all from the privacy and comfort of your own home. Our nurse practitioners make it easier for you to decide whether intermittent fasting is working for you and whether or not you should stop.

At Everlywell, we provide the tools you need on your weight loss journey, including vitamins, medications, at-home diagnostic testing, and virtual healthcare. Our full range of services can help give you the knowledge and power to take control of your health.

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References

  1. What is intermittent fasting? Does it have health benefits? Mayo Clinic. URL. Published May 5, 2022. Accessed January 31, 2023.
  2. Seimon RV, Roekenes JA, Zibellini J, Zhu B, Gibson AA, Hills AP, Wood RE, King NA, Byrne NM, Sainsbury A. Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials. Mol Cell Endocrinol. 2015 Dec 15;418:153-72. URL.
  3. Intermittent fasting: What is it, and how does it work? John’s Hopkins Medicine. URL. Accessed January 31, 2023.
  4. Calorie restriction and fasting diets: What do we know? National Institute on Aging. URL. Published August 4, 2018. Accessed January 31, 2023.
  5. Varady KA, Cienfuegos S, Ezpeleta M, Gabel K. Cardiometabolic benefits of intermittent fasting. Annual Review of Nutrition. 2021; 41:333-361. URL.
  6. Diet Review: Intermittent Fasting for Weight Loss. T.H. Chan Harvard School of Public Health. URL. Accessed January 31, 2023.
  7. Wing RR, Phelan S. Long-term weight loss maintenance. Am J Clin Nutr. 2005;82(1 Suppl):222S-225S. doi:10.1093/ajcn/82.1.222S. URL.
  8. Time to try intermittent fasting? Harvard Health Publishing. Published July 1, 2020. Accessed January 31, 2023. URL.
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