The health and wellness space is no stranger to diet trends. Joining the ranks of celery juice and ketogenic diets in popularity this year is intermittent fasting (IF). And while intermittent fasting has been making headlines, does this trending topic really deliver on its supposed health benefits? 

Intermittent fasting has been gaining popularity since 2012 when BBC broadcast journalist Dr. Michael Mosley released his TV documentary Eat Fast, Live Longer and book The Fast Diet. Journalist Kate Harrison’s book The 5:2 Diet based on her own experience, and Dr. Jason Fung’s bestseller The Obesity Code also generated much buzz on the effectiveness of intermittent fasting.

What Is Intermittent Fasting?

So what exactly is IF, and why all the hype? Also known as intermittent energy restriction, intermittent fasting is derived from traditional fasting, a universal ritual used for health or spiritual benefit as described in early texts by Socrates, Plato, and religious groups. IF is an umbrella term for various meal timing schedules that cycle between voluntary fasting and non-fasting over a given period. Promoters of IF claim that it can improve markers of health that are associated with disease and change body composition.

This voluntary fasting and non-fasting can be split up in a number of ways, including these popular methods:

Alternate Day Fasting

In Alternate Day Fasting, you alternating between days of no food restriction and days that consist of one meal that provides about 25% of daily calorie needs. For example: Mondays, Wednesdays and Fridays would consist of fasting, while the alternate days would carry no food restrictions.

5:2 Fasting

The 5:2 diet approach advocates no food restriction five days of the week, cycled with a 400-500 calorie diet the other two days of the week.

Time-Restricted Fasting

In Time-Restricted Fasting, there is a designated time frame each day for fasting. For example, meals are eaten from 12 – 8 PM, with fasting during the remaining hours of the day. The most popular time-restricted fasting is 16:8 (fast for 16 hours of the day, eat for 8 hours of the day).

Related: Looking for more nutrition tips, recipes and content from our Registered Dietitians? Check out our Nutrition section!

Potential Health Benefits of Intermittent Fasting

There is some emerging research on IF that looks promising in terms of potential health benefits such as fat loss, blood sugar control, and cognitive effects. However, there is still a lot of research that needs to be done on the long term effects in humans. 

Specifically for women, it is important to understand that the majority of studies done on IF is on animals and men. Females may react differently to fasting than men due to differences in hormones, so it is important to watch for changes in menstrual cycles or any other negative symptoms. 

Individuals with the following conditions should abstain from intermittent fasting:

  • Diabetes (advanced or on medication)
  • Eating disorders
  • Use of medications that require food intake
  • Active growth stage, such as in adolescents
  • Pregnancy, breastfeeding
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Potential Pitfalls of Intermittent Fasting

Interference with culture, work, and social settings.

Eating is so much more than just fueling our bodies and is a very social activity. Many celebrations, milestones, and special occasions revolve around food. With IF, it may be difficult to participate in social gatherings and other events.

Possible increased fixation on food.

Prolonged periods of food deprivation increases the risk for overeating when food is reintroduced, and may advance other unhealthy behaviors such as an increased fixation on food.

Possible negative side effects.

Side effects may include increased hunger, irritability, reduced ability to concentrate.

Nutrient needs may not be met.

When you restrict food, you restrict nutrients. If you are intermittent fasting, it is important to focus not only on timing of eating, but the foods you are eating to make sure you are getting a variety of nutrients.

The Bottom Line

When someone comes to me and asks about IF, the first thing I want to get down to is the WHY behind the reasoning for intermittent fasting. What are you seeking to accomplish? Is it weight loss? Blood sugar control? Increased energy? 

Intermittent fasting is not a magic pill, but it may help certain individuals with their health goals and eating patterns. If you don’t have any issues with hunger, headaches, lightheadedness, low blood sugar, or preoccupation with always thinking about food, then it may be beneficial if it is realistic for your lifestyle. 

If you do experience these symptoms, or if it isn’t realistic for your lifestyle, know there are many other ways to accomplish your health goals that do not require following a “diet”. Work with a Registered Dietitian to determine a personalized plan for your specific medical history, health goals, and lifestyle. 

Interested in learning more or speaking with one of our FFC Registered Dietitians? Email nutrition@ffc.com today to schedule a 15 minute discovery call!

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Post written by FFC Registered Dietitian Chelsea Rice.