Intermittent Fasting

Written by: Kimberly Tessmer, RDN, LD

What is Intermittent Fasting?
Curious about the intermittent fasting trend?  To put it in simple terms, intermittent fasting consists of eliminating or restricting calories over a specific period and alternating that with periods of regular calorie intake.  During fasting, you eat no solid food and drink only non-caloric beverages such as water, black coffee or unsweetened tea.

What is the Best Method for Intermittent Fasting?
There are several different ways that you can execute intermittent fasting.  The key is to find the method that best works for you and your lifestyle.

  • 16/8 Method: 8 hour eating window with 16 hours of fasting (this can be anywhere from 12 to 18 hours of fasting and the times in which you eat are completely up to you but for best effect make it earlier in the day such as between 10 am and 6 pm)
  • 5:2 Method: eating normally 5 days per week and strictly reducing calories (approximately 500 calories for women and 600 calories for men) 2 days per week; such as a Tuesday and a Friday
  • Alternate Day Fasting: Combination of complete fasting days (no calorie containing foods or beverages consumed) alternating with days of unrestricted food and beverage intake.  Much like the 5:2 method but doing a complete fast on the 2 days per week.

If the thought of Intermittent fasting tends to be overwhelming but you still want to try it, start slow with just once per week. The easiest way to get started is to extend your fast before and after your sleep cycle.  You already fast during sleep so if you stop eating a few hours before you go to bed and wait to eat a few hours after waking up you already have a 12 hour fast, assuming you sleep for 8 hours.  If you are unsure on how to work with intermittent fasting to reach your health goals, consult with a dietitian who can help you devise a plan that is right for you.

Will Intermittent Fasting Help Me Lose Weight?
Intermittent fasting is not necessarily a “diet” but for those that struggle with consuming too many daily calories, it can help to decrease the amount of food they eat in a day if they are mindful.  In most cases, intermittent fasting will not automatically change what and how much you eat but it will change when you eat. As a dietitian I feel obligated to mention that intermittent fasting is no magic bullet to weight loss.  If you tend to fast and then over-indulge during your eating window, weight loss will be difficult.  It is still important to ensure you are eating healthy well-balanced meals and especially watching portion sizes if weight loss is your goal.

Is Intermittent Fasting Safe for Everyone?
Intermittent fasting may not be the best option for everyone.  If you have a history of disordered eating habits, then this type of eating plan may be a trigger and not your best bet.  For women who are pregnant, breastfeeding or trying to get pregnant, it is best to avoid intermittent fasting.  Individuals with certain health issues that need higher calorie levels, those on certain medications or those that are diabetic may be putting themselves at risk by following intermittent fasting. Although some studies have shown that intermittent fasting may improve heart health, lower total cholesterol, benefit weight loss and reduce inflammation, many dietitians remain skeptical. If you are not sure if this type of eating pattern is safe for you, always consult with your doctor before starting.


Sources:

  1. Orenstein, B. W.  Intermittent Fasting: The Key to Long-Term Weight Loss?  Today’s Dietitian. December 2014: Vol. 26 No. 12 Pg. 40. https://www.todaysdietitian.com/newarchives/120914p40.shtml
  2. Tello, MD, MPH, Monique. “Intermittent Fasting: Surprising Update”. Harvard Health Publishing.  Harvard Medical School, Feb. 10, 2020; accessed 2/6/2020. https://www.health.harvard.edu/blog/intermittent-fasting-surprising-update-2018062914156
  3. Gleeson, Racey, Jane. “Intermittent Fasting: Is it Right for You?”. Michigan Health. University of Michigan/Michigan Medicine, July 29, 2019; accessed 2/8/2020. https://healthblog.uofmhealth.org/wellness-prevention/intermittent-fasting-it-right-for-you
  4. Leonard, Jane. “A Guide to 16:8 Intermittent Fasting”. Medical News Today. Jan. 2, 2020; Accessed 2/7/2020. https://www.medicalnewstoday.com/articles/327398.php
  5. Gordan, Barbara, RDN, LD. “What is Intermittent Fasting?”. Academy of Nutrition and Dietetics. Eatright, May 7, 2019; accessed 2/8/2020. https://www.eatright.org/health/weight-loss/fad-diets/what-is-intermittent-fasting
  6. “Not so Fast: Pros and Cons of the newest diet trend”. Harvard Health Letter. Harvard Medical School, July 31, 2019; accessed 2/8/2020. https://www.health.harvard.edu/heart-health/not-so-fast-pros-and-cons-of-the-newest-diet-trend
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