Intermittent Fasting

Published Date: March 26, 2018

Intermittent fasting

Intermittent fasting is a term used to describe dietary approaches that focus on cycling between prolonged periods of fasting and eating during defined periods of time.

The periods of fasting involve intentionally fasting for longer than the traditional 8-12 hours of overnight fasting that naturally occurs during sleep after the evening meal until breakfast the next morning.

Benefits of intermittent fasting may include:

  • Reducing average daily calorie intake resulting in weight loss
  • Improving diabetes control and insulin resistance
  • Reducing blood pressure
  • Improving cholesterol
  • Reducing inflammation

The two main categories of fasting are whole-day fasting and time-restricted eating, each of which have a variety of approaches as well as pros and cons:

  • Whole-day fasting involves not eating for one or more days at regularly scheduled intervals. An aggressive approach is alternate-day fasting, where a day of regular eating is alternated with a day of complete fasting (having only non-caloric drinks) on a regular basis. Since this approach can be challenging to do for many, some people advocate for a less aggressive approach called the 5:2 diet, where fasting is done only two days of the week and a small number of calories (up to 500) is allowed on the two fasting days.
  • Time-restricted eating (TRE) is a less aggressive approach, but for some people TRE is a more sustainable approach. With this method, eating is restricted to a certain number of hours per day, and this approach is done every day of the week. For example, some people will limit their food intake to an 8-hour window of the day between 10 AM and 6 PM, followed by 16 hours of fasting. Others limit food intake to a 6-hour window between noon and 6 PM.

Intermittent fasting can also be highly individualized and adjusted for each person based on hunger levels, goals, and interest. The greatest benefits of intermittent fasting occur the longer the fasting period and the shorter the eating window.

Precautions: Fasting is not recommended in children or in women who are pregnant or nursing. Patients who take medications for diabetes or high blood pressure should consult with a healthcare provider before trying intermittent fasting, as these medications might need to be adjusted while fasting.

Photo courtesy of the Obesity Action Coalition.

Frequently Asked Questions

Is intermittent fasting safe for everyone?

No.  Although intermittent fasting is safe for most people, you should always check with your healthcare provider before attempting the practice.  Some medications, especially those that affect blood sugar, can make intermittent fasting difficult and possibly even dangerous.

Written by Jeffrey Sicat, MD, FACE, FOMA

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