What days should I fast — and will the weight stay off?

Q: Should I start by doing 800 calories every day?

The first decision you need to make is whether you want to start on the fast-track 800 calories-a-day diet, or the new 5:2 plan of 800 calories on two days a week.

The answer depends on your motivation levels and how much weight you want to lose. The advantage of the fast-track option is, of course, that the weight loss will be dramatic, and that can be very motivating — but you need to be sure that you are comfortable about trying it.

I suggest that you commit to this stage for two weeks, then reassess.

Q: How do I choose my 800-calorie days?

I am often asked whether it is better, when doing the 5:2, to do your 800-calorie days back-to-back or split them up.

When I started out, I didn’t think it would make any difference which days I fasted, so I opted for Tuesdays and Thursdays. This was mainly a process of elimination. I didn’t want to curtail my social life by choosing Fridays or weekends. Monday fasts struck me as an unappealing way to start the week.

When I initially tried doing my fasts back-to-back (Tuesdays and Wednesdays), I found it inconvenient, but it is a pattern I tend to follow now.

In theory you may be better off keeping fasting days back-to-back if you can, because that helps you get the maximum fat-burning benefit of two days of calorie restriction, and your body should stay in fat-burning mode (ketosis) for the whole of the second day. Some people also find it more convenient to get their fasting over and done with in one go.

You may, however, prefer to split your days. Just find a solution that works best for you. My only advice is that when you have chosen your days, try to stick with them week after week. Being flexible about your fast days could mean you are less likely to complete them.

Q: When should I eat on an 800-calorie day?

Everyone is different. When I’m doing the 5:2, I prefer to use up the majority of my calories in just two meals and put aside a few for a small snack.

I have a late breakfast, skip lunch and aim to eat early in the evening. As you’ll see in this week’s pullouts, including today’s, our menus offer a huge choice.

You can have three smallish meals — breakfast, lunch and dinner — or spread the calories over two larger meals. Try each approach until you the find one that works for you.

Q: If I lose weight rapidly, will I put it back on as soon as I stop dieting?

No. Studies that have run for more than a year show weight regain was no more a problem for those who lost weight rapidly than those who lost it gradually.

In fact, rapid weight-loss dieters lost, and kept off, far more weight. An Australian study which put 200 obese volunteers on an 800-calorie rapid weight-loss diet for 12 weeks found that not only did they lose more weight than steady dieters, but four years later they were still leaner.

Q: Does it matter what I eat if I stay under 800 calories?

I strongly recommend you eat a Mediterranean-style diet rather than making up a diet for yourself. Please don’t even think about one of those crazy cabbage soup or green juice diets.

Even though you’ll be eating less, you won’t be getting a good balance of nutrients.

The menus in this series have been created to be safe and sustainable. Whatever you eat, it is vital that you get enough daily protein (at least 50-60g a day), otherwise you risk losing muscle. You also need to be sure you have a balanced mix of all the other essential nutrients.

Q: Won’t my metabolism crash if I go on a rapid weight-loss diet?

Fear of going into ‘starvation mode’ is one of the reasons so many people think diets, particularly rapid weight-loss diets, don’t work. This myth is based on the Minnesota Starvation Experiment, carried out during World War II, in which slim young volunteers lived on a low-calorie diet (about 1,500 calories a day) consisting mainly of turnips and potatoes. After six months on this very low-protein diet, when their body fat had fallen to less than 10 per cent, their metabolic rate (the amount of energy your body uses to keep itself going) crashed. But this was an extreme situation. More recent experiments on the effects of short-term calorie restriction have produced very different results. In fact, it has been shown that shortterm fasting can have the opposite effect and actually boost your metabolic rate.

Q: If I do put the weight back on, will I be worse off than before?

No one who goes on a diet intends to put the weight back on, but it happens. When I asked Susan Jebb, professor of diet and population health at Oxford University, if that matters, she said, emphatically, no.

‘The harmful effects of obesity come from how big you are and from how long you’ve carried that extra weight. Even if you have a few years where you are lighter than you would have been, that brings very substantial health benefits,’ she says.

She adds that you should weigh yourself regularly and, if you find you are regaining pounds, you should act quickly to stop it progressing. A few pounds can soon turn into a lot of pounds.

Q: Should I avoid exercise on 800-calorie days?

There is no reason to stop exercising just because you’re fasting. Exercise can help to burn fat and preserve muscle mass. But I wouldn’t recommend prolonged intensive exercise on fast days.

I find doing press-ups and going for short runs is both possible and usefully distracting when I’m fasting.

Being active is a great way of taking your mind off food, and will boost your mood into the bargain.

Q: Can I do this diet if I’m a vegetarian or vegan?

The abundance of vegetables and legumes in the recipes in this series make this diet ideal for a vegan or vegetarian lifestyle. Many of the dishes are suitable for both. Where possible, we suggest tips and swaps for vegetarians.

However, do be aware that some vegan alternatives, such as coconut yoghurt, might be higher in calories than their dairy counterpart.

Q: Do I need to take a vitamin supplement?

The menus in this diet plan are designed to ensure that you get all the necessary minerals and vitamins.

Nonetheless, you may, as a precaution, want to try a reputable brand of multivitamin and minerals, particularly on fast days. You might also want to take fish oil supplements from a decent brand.

In normal circumstances I’m not a big fan of either, but it’s better to be safe.

Q: How long should I spend on the fast-track before switching to 5:2?

If you choose to kickstart your weight loss with my fast-track plan, it is entirely up to you when you move on to the new 5:2. You might find a couple of weeks of rapid weight-loss enough, or you might want to stay in the fast-track stage for longer. It depends on what you’re trying to achieve, and how you’re getting on.

Either way, you should notice your hunger levels and cravings will be greatly reduced. You should also find you are feeling more energetic, lighter and brighter — and people will have begun to comment on how well you are looking!

Switching over is straightforward and can be done at any point which suits you. ADAPTED by LOUISE ATKINSON from The Fast 800 by Michael Mosley, published by Short Books at €11.99. Find information, support and advice at thefast800.com. For more information on Dr Michael Mosley and for live dates see michaelmosley.co.uk.