Want to know how to exercise on the 5:2 but scared of keeling over? Don't be. It's simple, safe and supremely beneficial

Any products in this article have been selected editorially however if you buy something we mention, we may earn commission

With two days of fasting alongside a general healthy eating plan on the original 5:2 diet , the prospect of having to introduce an exercise plan sounds simply terrifying and quite frankly, exhausting. The very thought sent frantic questions buzzing around GTG HQ - how much exercise should we do? Is it OK to exercise on a fast day? Will we collapse?

The  The Fast Beach Diet Book  (£7.99, Amazon) written by 5:2 co-author Mimi Spencer adds exercise alonside 5:2 recipes  as a key factor in greatly speeding up the weight-loss process and improving overall fitness, strength and health. It's safe and will benefit you more in the long-run. Although if that’s not quite convincing enough for you, here’s our breakdown of what, when, how and why on 5:2 and exercise.

Can I exercise on a fast day?

Yes - research has shown that fasting has absolutely no negative effects on the ability of a person to perform short-term, high-intensity workouts or longer-duration, moderate-intensity exercise.  In fact, Mimi argues that training on a fast day can lead to “better metabolic adaptations”, which means enhanced performance over time and also means your body is forced to burn up fat stores rather than use energy recently consumed from food.  However, if you’re not used to doing much exercise, start slowly and listen to your body - don’t overdo it on a totally empty stomach. As with any diet or exercise regime, people's bodies react differently and the most important thing is to stay safe and healthy.

When should I eat if I’m exercising on a fast day?

It’s totally up to you. As with any other normal fast day, just split the calories in a way that best suits you. There are just a couple of things to remember; don’t attempt HIIT  immediately after eating as you run the risk of vomiting and cramping. Don’t load up on carbs before doing HIIT, unless you are exercising heavily for more than an hour at a time (you have plenty of stored carbohydrates on board). Finally, don’t load up on carbs after HIIT training either - you may feel a little weak but the whole point of HIIT is to deplete the energy stored in your muscles in order to make way for fresh glucose to be deposited into the bloodstream.

MORE GLOSS: Recipes and inspiration for fast days

When is the best time to exercise?

It’s widely accepted that whilst early morning exercise is often a struggle it can be a fantastic mood booster that sets you up mentally for the day. Research from Glasgow university showed that women in an 8.15am aerobics class achieved a 50 per cent boost in positive feelings compared to just 20 per cent for those who worked out at 7.15pm. Working out before breakfast also helps kick start your metabolism, which is more beneficial to weight loss in the long-run. Largely though, just find a time that best suits you - morning or evening, what all experts agree upon is that exercise at any time is better than none at all.

MORE GLOSS: How to succeed at the 5:2 diet, according to Dr. Michael Mosley

What type of exercise should I do?

As Dr Michael Mosley discovered in The Fast Exercise Book, high intensity interval training  (HIIT) is as effective, if not more, than high-volume training. Not only is it much easier to do but it also takes up much less time. Just seven minutes of high intensity exercise a couple of times a week can lead to massive improvements in aerobic fitness and endurance, reduced body fat and increased body strength. Why? Because when you push the intensity of a workout, you build more metabolically active muscle, and, because muscle is efficient at burning fat, your total calorie expenditure soars.

It doesn’t matter if you run or cycle or even swim - as long as you interchange intense bouts of exercise with longer periods of recovery and rest, it’ll do the job. Most importantly though, try to engage in exercises that you find fun. If you can make your exercise regime enjoyable, there’s a much higher chance of you integrating it into your lifestyle in the long-run.

How often should I exercise?

Aim to do three sessions of high intensity activity  a week. On the other two days try and introduce strengthening exercises such as 5 minutes of push ups, a plank before bed or even 50 crunches to help define and tone. You may be tempted to do more but don’t - the point here is quality not quantity, and you don’t want to burn out.

MORE GLOSS: What we learned from Michael Mosley's Lose a Stone in 21 Days