Many promote intermittent fasting (IF) as a magic bullet to weight/fat loss; that you can eat as much as you like in the feeding window and still drop weight/fat. Others tout it as having superior weight/fat loss benefits to other diets – even when calories are matched. But does it really? IF isn’t all that new – it’s actually been around for a lot longer than most people realise – which, thankfully, means it has a lot of research performed on it. We delve into what the science has to say and how IF can be used to help you lose weight.
IF is also known as time-restricted eating/feeding or intermittent energy/calorie restriction. Essentially, it just means you restrict your eating at times by fasting. IF is generally used by people to assist with weight/fat loss.
For weight/fat loss, this reduced window of eating should result in reduced calorie intake and thus a calorie deficit. If it does, it’s an effective means of losing weight/fat.
There are 3 different types of intermittent fasting:
- Alternate day fasting (ADF): 24-hour fasting alternated with 24-hour feeding.
- Whole day fasting (WDF): 2 days within the week of fasting.
- Time-restricted feeding (TRF): Reduced feeding window daily.
Note: A fasting day does not necessarily mean no food at all – it may be just be very low-calorie intake (≤800kcals)(1).
TRF is the typical method of IF used by people. Typically, this involves fasting for 16-20 hours with a feeding window of 4-8 hours (e.g., fasting from 8 PM to 12 PM the next day).
There have been a total of 55 studies completed comparing IF to continuous energy restriction (CER) for weight loss. The result? ALL of those studies determined IF had equivalent outcomes to CER (2,3). Yep, there was no greater benefit to just consuming the same number of calories in a continuous manner.While it’s not magic, if it helps you to achieve, sustain & adhere to a calorie deficit then it will work and could be a great tool for you to help control your calorie intake. However, if you find restricting your eating time to cause you to get extremely hungry, make poor food decisions, obsess over food, and/or negatively impact your mood, energy and training performance, then it may not be ideal for you and the same results can be achieved by simply controlling calorie intake while eating over a greater window, which can be facilitated by any dieting method reduced portion size, meal frequency, food choices, etc, etc.
Personally, it’s not for me on a continual basis. However, it doesn’t need to exist as a standalone method. People nowadays seem to think you must pick a side; IF or CER, like as if it’s religion! Some days, if I have an event where I’m socialising, dining out, etc., (all a distant memory during lockdown at the moment!) and I’d like some additional calories for it, then on that day I may push back my first meal and enjoy those calories later at the event. At the end of the day, weight/fat loss is determined by a negative energy balance; there are many tactics/strategies you can use to navigate through life while being on track and this is just one tool. Therefore, it makes sense treat it as such – a tool to use when needed – to allow for enhanced flexibility opposed to a structured rigidity.
