With a variety of new diets making the rounds, it becomes difficult to gauge which is the right one for you as an individual to follow. A lot of information is available, but which is actually factually correct is the bigger question!  Off late, fasting diets have been making the rounds, with intermittent fasting in the spotlight. This article aims to provide an unbiased view on intermittent fasting, so you can decide if it is sustainable to follow!

What is intermittent fasting? How is it different from the conventional weight management strategies?
Intermittent fasting (IF) involves cycling normal daily caloric intake (feeding) with periods of fasting or severe energy restriction. The period of fasting is not a true fast where food and/or water is not allowed (1).  In comparison, the conventional weight management strategy, continuous energy restriction (CER) that is, a calorie deficit, is used to induce weight loss by creating a daily energy deficit.
How does it work?
There are several fasting regimes and modified fasting regimes being practiced. The most popular IF methods are:

  • 5:2 diet, which involves 2 days (consecutive or non consecutive) of ‘fasting’ (energy intake of ~500kcal and ~600kcal are allowed for men and women respectively) and 5 days of regular eating patterns per week (1)
  • The Alternate Day Fast (ADF) involving alternate days of fasting and feeding (1)
  • The 16/8 diet, characterised by fasting for 16 hours a day and eating within an 8 hour feeding window.


What does the science say?

Weight loss: Intermittent fasting, like the media has portrayed, is not a magical diet to help induce weight loss. Rather, it is a tool to induce an energy deficit. However, if you compensate for the meals skipped during the feeding period, you wouldn’t observe results. A recent meta analysis of 4 studies concluded that IF methods are suitable for inducing short term weight loss, however, the variability between the study duration and participant characteristics (2) . Rather, intermittent fasting methods have been found to induce similar weight loss (3, 4) or no significant difference in weight loss (1) when compared with CER. This further strengthens the argument that while IF can induce weight loss, it is merely a tool to induce an energy deficit.
Metabolic outcomes:  You must think, if not weightloss maybe IF has an effect on metabolic outcomes like triglycerides, glucose and cholesterol among others? A systematic review and meta analysis of IF and CER found no significant differences  in glucose, HbA1c, triglycerides, HDL and LDL cholesterol (3).  Further, another systematic review showed that insulin and insulin sensitivity was comparable between IF and CER methods (5). However, definite conclusions cannot be drawn due to the varying methodologies of the individual studies. Further research is needed in order to understand this completely.

Should I try it?
Intermittent fasting is not for everyone. That is, if you are pregnant, breastfeeding, have a history of or an existing eating disorder, are extremely underweight or are on medication that require food intake, kindly avoid practising this regime.
If you are  person that does well without a meal and are comfortable with periods of fasting, you could give this a shot!

References:

(1) Harris L, Hamilton S, Azevedo L, Olajide J, De Brún C, Waller G et al. Intermittent fasting interventions for treatment of overweight and obesity in adults. JBI Database of Systematic Reviews and Implementation Reports. 2018;16(2):507-547. 
(2) Ganesan K, Habboush Y, Sultan S. Intermittent Fasting: The Choice for a Healthier Lifestyle. Cureus. 2018;10(7):e2947.
(3) ioffi I, Evangelista A, Ponzo V, Ciccone G, Soldati L, Santarpia L et al. Intermittent versus continuous energy restriction on weight loss and cardiometabolic outcomes: a systematic review and meta-analysis of randomized controlled trials. Journal of Translational Medicine. 2018;16(1):371.
(4) Sundfør T, Svendsen M, Tonstad S. Effect of intermittent versus continuous energy restriction on weight loss, maintenance and cardiometabolic risk: A randomized 1-year trial. Nutrition, Metabolism and Cardiovascular Diseases. 2018;28(7):698-706.
(5) Barnosky A, Hoddy K, Unterman T, Varady K. Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research. 2014;164(4):302-311.

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