24 July 2019
An Introduction to Intermittent Fasting
Does intermittent fasting live up to the hype? And how to get started? Here’s the need-to-know.
Over the past few years, the practice of intermittent fasting has become big business. Also known as time-restricted eating (TRE), even if you haven’t heard its proper name, you’ll more than likely be familiar with the concept: the 5:2 diet and the 16:8 method are just a couple of examples.
Proponents of intermittent fasting believe TRE works alongside the circadian rhythm - the body's inbuilt clock - and in doing so gives your body the time it needs to digest the food you eat and to use it most effectively. By extension, many have reported enjoying better sleep, having more energy, a higher level of mental clarity and experiencing less bloating.
Also credited with teaching participants what real hunger feels like, rather than just snacking out of habit
, it’s become a useful tool for people hoping to lose those last few stubborn pounds.
So, does intermittent fasting live up to the hype? And how to get started? Here’s the need-to-know.
What is intermittent fasting?
While different approaches to intermittent fasting exist, all follow a similar principle: eating all your meals (and snacks) within a set time frame and fasting for a set period – this could be a matter of a few hours or even a full 24 hours.
During your ‘eating time’ you have the freedom to choose your own meals, although if you want the best results you’ll still want to keep your food choices in line with a nutritious, balanced diet. So no, unfortuantely this doesn’t mean that you can gorge on pastries all day.
"While fasting can be a helpful tool for eating, the most important thing is to ensure you’re following your calorie and macro goals" explains Greg Gallagher, a Canadian fitness expert better known as Kinobody who has played a major role in bringing intermittent fasting to public attention.
During your fasting time, on the contrary, you don't eat at all. After a certain period of fasting insulin levels decrease and the body switches to a state of ketosis, where it burns fat in order to provide energy.
What types of intermittent fasting are there?
Although numerous types of intermitted fasting exist, there are three main strategies:
5:2 – Among the most well-known of intermittent fasting schedules is the 5:2 plan, which consists of consuming your normal RDA calories for five days of the week, with your calorie count restricted to 500 for two days per week.
16:8 – Perhaps the easiest intermittent fasting plan to incorporate into your lifestyle, the 16:8 was popularised by personal trainer, author and Balance Festival speaker Max Lowery, and requires followers to fast for 16 hours per day, fitting their calorie intake into an eight-hour window of their choice.
Alternate Day Fasting – Arguably the most intimidating of the methods, this programme requires followers to sustain full 24-hour fasts across a set number of (alternating) days per week. Starting for example on a Monday night and continuing until the following evening, you never actually go an entire day without a meal.
Is intermittent fasting relatively new?
As Dr Adam Collins, a Senior Teaching Fellow at the University of Surrey, explained to the Balance Journal in What's Intermittent Fasting? the principle is nothing new: “Fasting might be popular now but it is not a new concept. In humans, much of our understanding of the effects of fasting have come from observations of religious practices (e.g. Ramadan) or individual protests (e.g. hunger strikes) or as a consequence of natural and man-made disasters, brought about by drought, famine and/or war.”
What are the health benefits of intermittent fasting?
It's not only your time that it saves; although quality research into the effects of intermittent fasting on humans is still limited and the lifestyle requires further investigation, early studies have shown that it has the potential to improve insulin resistance, improve cholesterol levels and minimise the risk of developing Alzheimer’s disease, as well as the decelerate and even prevent of chronic inflammatory diseases (1).
According to one study by the University of Surrey, focusing on the 5:2 approach, intermittent fasting also “clears fat from the blood quicker after eating meals compared with daily calorie restriction diets, reducing an important risk factor for cardiovascular disease.” The study further found “a greater reduction in systolic blood pressure” in those following the 5:2 diet, compared to those following a more traditional calorie-controlled diet.
If you’re considering intermittent fasting for weight loss then the good news is that it’s believed to be more sustainable than maintaining consistent calorie restriction. This, combined with the fact that you have less hours in the day in which to eat and so you’re less likely to overeat, means overall calorie intake is generally lower, resulting in weight loss.
How long can you do intermittent fasting for?
There’s really no set time limit – some people choose to undertake it for a set amount of time in order to meet a specific goal, but it is notable for being designed as a lifestyle as opposed to a diet. Max Lowery, for instance, describes having discovered it by accident a number of years ago and has never looked back since: “It has had such a profound effect on my life that I set out on a mission to make it as accessible as possible for everyone else.”
Who should avoid intermittent fasting?
It’s got to be said that intermittent fasting isn’t for everyone. Experts recommend against following the plan if you have a history of disordered eating, live with type 1 diabetes or low blood pressure, are already underweight or are pregnant or breastfeeding.
- Forsch Komplementmed.. Dec 16 Fasting therapy for treating and preventing disease - current state of evidence. 2013; 20(6):444-53