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All about intermittent fasting

Nutrition · Oct 20, 2020

A popular trend in dieting isn’t about eating certain foods. It’s about eating no foods – for a while, at least.

Intermittent fasting, during which dieters forgo food for various lengths of time, has become a buzz term lately. But fasting itself is not a new phenomenon.

Abstaining from food has been done for centuries for many different reasons, by many different cultures. But in the information age, it has become a widespread strategy for losing weight.

As the name suggests, intermittent fasting incorporates various periods of fasting and non-fasting. Three most popular forms include:

  1. Feeding window — fasting for 16-20 hours and eating within a 4-8 hour window, most commonly between 12 and 8pm every day.

  2. The 5:2 — fasting for a full 24 hours for 2 days per week and then eating on a regular schedule for the remaining 5 days.

  3. Random meal skipping — assuming a typical three-meal plan with no snacking, one meal is skipped each day, usually alternating the skipped meals from day to day.

Does intermittent fasting work for weight loss?

Usually, yes. Intermittent fasting can, and probably will, help you lose weight. The caloric restriction that results when you skip meals or restrict the amount of time you eat will most likely create an energy deficit, leading to weight loss.

Of course, any diet that helps you restrict calories will almost always help with weight loss.

For example, a recent study1 that compared one group of intermittent fasters using the 5:2 method with a group of non-fasting dieters that ate the same amount of calories with no time restriction found there was no difference in the weight lost between the groups.

However, that same study also found that the participants taking part in intermittent fasting reported higher hunger scores than the group on a non-fasting diet. In my experience, if you are hungry day after day while on a diet, the chances of being able to follow your diet in the long term dramatically decrease.

I would also not recommend intermittent fasting, specifically the meal-skipping variety, for someone living with diabetes, as it has been shown to increase blood glucose after eating and may increase chances of hypoglycemia when using certain diabetes medications. It is also not recommended2 for pregnant women or those with disordered eating.

Can intermittent fasting improve overall health?

Depending on which type of fasting you choose, there are potential risks of dehydration and constipation, as well as nutrient deficiencies. If you’re thinking of trying intermittent fasting, consult your dietitian to discuss the best approach.

What diet is the best diet?

Alas, there is still no solid evidence that there is one diet to rule them all. Comparative diet studies3 have shown no difference in weight loss between some of the most popular diets (e.g., low-carb, low-fat).

Our nutrition team coast to coast can help you make sense of popular nutrition trends, and develop a dietary plan that works best for your life and your goals. Get in touch to learn more today.


1 T.M. Sundfor, M. Svendsen, S. Tonstad. (2018, March 29). Effect of intermittent versus continuous energy restriction on weight loss, maintenance and cardiometabolic risk. Retrieved from: https://www.sciencedirect.com/science/article/abs/pii/S0939475318301005?via%3Dihub

2 Daniela Jakubowicz, Julio Wainstein, Bo Ahren, Zohar Landau, Yosefa Bar-Dayan, Oren Froy. (2015, July 28). Fasting until noon triggers increased postprandial hyperglycemia and impaired insulin response after lunch and dinner in individuals with type 2 diabetes. Retrieved from: https://pubmed.ncbi.nlm.nih.gov/26220945/

3 Christopher D. Gardner, John F. Trepanowski, Liana C. Del Gobbo, et al. (2018, February 20). Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion. Retrieved from: https://jamanetwork.com/journals/jama/article-abstract/2673150?redirect=true

Authored by:
Rob Lazzinnaro
Registered Dietitian

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