If you find the title of this column interesting then probably you already have some experience with intermittent fasting, or you know about it and want to try it. Intermittent fasting (IF) has become very popular in the last few years. You may have heard some amazing success stories but maybe also some not so positive results as well.
Most of us are looking for an easy way to lose fat and gain muscle and strength, and IF can be a very beneficial tool for many people. Especially when you consider that we are all surrounded by lots of fast foods, ultra processed foods, and almost every social event involves some type of food. I actually find that many of my clients prefer time restricted eating and find it easier than eating whenever they want but with a calorie restriction. Some studies do support that IF can be very beneficial, especially for people who struggle to stick to their diet seven days a week, or for people who are type 2 diabetic. Of course you should be very careful as to whether this approach fits your lifestyle or not, because if not then you may see more damage than benefits.
There are many ways to apply IF, including 14–10, 16–8, and 18–6. These refer to the hours in the day — for example, 14–10 means that you fast (don’t consume anything) for 14 hours and consume all of your calories (solids and liquid) within a 10 hour timeframe. In 18–6 you’re only eating within a 6 hour timeframe each day, for the remaining 18 hours you’re fasting.
There are however a couple of other very effective and popular strategies — 5:2 and alternate day fasting. You may find it easy to do a 5:2 fasting approach, which means that each week on two days of your choice you consume only 500 to 750 calories a day, but on the remaining five days you eat normally. Some people find this much more manageable than trying to eat less calories all the time, and it can also be very beneficial for blood glucose (sugar) control and can even help reduce your hunger on the following days too. Although eating under your maintenance calorie level is probably not optimal if your goal is hypertrophy (muscle gain), when you combine it with resistance training and an adequate protein intake this will improve your body composition and your strength.
IF is not necessarily a better choice than a calorie restricted diet, just some people do find it much easier to control their hunger and can therefore stay longer on their diet. However, if your goal is to gain muscle then you need to make sure you are getting enough protein and calories on your non-fasting days. And, of course, you need to do some type of resistance training to support your goal.
I think many people are successful on a 5:2 or other IF approach because of its simplicity. Just do make sure that this approach fits in with your lifestyle, and especially if you have a history of any type of eating disorder then it can be a very bad idea to try for you.
Remember, all of the IF strategies ultimately come down to some type of calorie restriction. So even if you are practicing IF regularly, but consuming too many calories in your non-fasting hours or on your non-fasting days, it will not be beneficial from a weight loss perspective — although weight loss is of course only one part of the many benefits of fasting.
Before you start any type of diet, ask yourself “Can I add this into my lifestyle for at least 3 to 6 months?”. As always, if you have any current medical concerns please ask your physician before trying any of the intermittent fasting approaches.
University of South Australia (July 2018). World-first study shows benefits of 5:2 diet for people with diabetes. https://unisa.edu.au/Media-Centre/Releases/2018/World-first-study-shows-benefits-of-52-diet-for-people-with-diabetes
Plos (November 2021). A randomised controlled trial of the 5:2 diet. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0258853
National Library of Medicine (November 2021). A randomised controlled trial of the 5:2 diet. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8598045/
National Library of Medicine (December 2016). Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting. https://pubmed.ncbi.nlm.nih.gov/27062219/
National Library of Medicine (June 2022). Intermittent fasting and continuous energy restriction result in similar changes in body composition and muscle strength when combined with a 12 week resistance training program. https://pubmed.ncbi.nlm.nih.gov/35084574/
National Library of Medicine (February 2023). Intermittent fasting and protein pacing are superior to caloric restriction for weight and visceral fat loss. https://pubmed.ncbi.nlm.nih.gov/36575144/
JAMA (July 2018). Effect of Intermittent Compared With Continuous Energy Restricted Diet on Glycemic Control in Patients With Type 2 Diabetes. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2688344