It’s becoming popular as a fat-loss tactic, but is it effective long-term for a lean physique? Trainer and nutrition expert (and MF cover guy this issue) Scott Baptie takes a look.

What is intermittent fasting?

Intermittent fasting (IF) means restricting the amount of food you eat for a given period, followed by a period of normal eating. It’s growing in popularity, among both fitness enthusiasts and the wider population, as a fat-loss tactic — but it is still controversial. This is because it challenges many established beliefs, such as the importance of frequent eating and meal timing to prevent muscle breakdown. However, proponents of IF say it has multiple benefits, including improving body composition and reducing fat stores while increasing muscle mass.

How would I do it?

There are many ways in which people can approach IF. There’s the alternate-day fast, in which you restrict your calories every other day, a fast once in every seven days, or a fast every third day. However, the one that’s achieved recent prominence is the 16-8 method, when you spend 16 hours a day fasting and the remaining eight hours feeding.

Does it work?

Research shows a variety of benefits of intermittent fasting. Studies conducted on animals have demonstrated increased lifespan thanks to fasting and calorie restriction. Studies have been done on humans too, but the findings aren’t as concrete. However, they are positive in that they demonstrate IF raises insulin sensitivity — which means your body is more efficient at processing nutrients —  and lowers body-fat levels and blood pressure.

What are the disadvantages?

Not surprisingly, hunger is a problem for many people. Not eating for long periods between meals is something we in the developed world are unused to. Also, research shows that a higher meal frequency is better for maintaining feelings of fullness.

A bigger issue for those who train regularly is increased expenditure of muscle tissue for energy. Pre-workout carbohydrates and protein in the form of essential amino acids reduce the amount of muscle used for fuel, which would be higher when working out on an empty stomach. Eating before training also increases protein synthesis, or the building of new muscle tissue, which is also helped by eating high-protein meals consistently through the day.

Many IF protocols also preclude breakfast. Although this may be beneficial for fat loss, eating first thing in the morning has been shown to improve memory, concentration and food-choice discipline later in the day.

What are the advantages?

As well as improving your body’s ability to process nutrients through increased insulin sensitivity, IF has also been shown to reduce levels of body fat. It does have more practical advantages too — you don’t have to worry about preparing meals in advance to ensure you get the right nutrients, and it’ll probably save you money since you’ll be eating less overall.

So should I do it?

As with any nutrition goal, it really depends on your individual goals, physiology, preferences, lifestyle and a host of other factors. Research on IF demonstrates there are both pros and cons associated with the approach. Besides, anyone who claims their nutritional methodology is the single best approach to fat loss is misguided — there are many ways to skin a cat.

FAST FACTS

Here are three of the most popular fasting methods. See which one best suits you.

16/8

Sometimes known as “Leangains”, a term popularised by author Martin Berkhan, this simply means restricting your eating to an eight-hour period each day. Most people who do it will fast from 9pm to 1pm, train, and then eat two or three large meals in their eight-hour window.

20-4

Based on the feeding patterns of Roman and Spartan soldiers, this consists of 20 hours of fasting, then a four-hour feeding window. It’s arguably the simplest form of IF, but many find it tough to eat clean when they need to consume 2000 calories in one sitting.

5:2 Diet

Popularised in a TV show and best-selling book by UK doctor Michael Mosely, over a week, the 5:2 diet requires you to eat normally for five days and on two non-consecutive days consume only 600 calories — say, in two small meals.

Scott Baptie is a sports nutrition consultant, physique transformation specialist and director of Food For Fitness (foodforfitness.co.uk).