Do I need a vitamin boost?

Whether you’re wondering how many weeks you can survive on 800 calories a day or how to choose your ‘fast’ days on the New 5: 2, we can give you the answers.

Below, Dr Michael Mosley and Dr Clare Bailey tackle some of the most frequently asked questions about the programme.

QHow long is it safe to do the Fast 800?

A It’s entirely up to you whether you choose to kick- start your weight-loss programme with the fast-track 800 calorie plan — and also how long you choose to stay on this.

rapid weight loss for up to 12 weeks has been shown to be safe in several studies, as long as you follow recommendations and drink lots of water.

some people continue for longer but we advise that once you reach your goal or at three months, you introduce weekly non-fasting days.

QShould I drink more on 800-calorie days?

A BeINg dehydrated is the main reason people give up on fast days; it leaves you feeling feeble, light-headed and with brain fog — symptoms often mistakenly blamed on a low-calorie regime.

When you cut back on calories, not only do you miss the fluid in food, you also lose water as your body breaks down fat. Many people drink 1–1.5 litres extra each day.

QHow do I pick fasting days on the New 5:2?

A thIs Is a question we’re often asked. In theory, you may be better keeping your fasting days back-to-back as you get the maximum fat-burning effect of two days of calorie restriction and your body should stay in fat-burning mode (ketosis) for the whole of the second day.

however, you may prefer to split your days instead, keeping Friday nights or sunday lunchtimes free.

Our only advice is to stick with the pattern you choose: being flexible about fasting days may mean you do not do as many as you’d intended.

QA As A rule of thumb, the less processed the oil the better. Cold-pressed oils, such as extravirgin olive and rapeseed oil, are minimally processed, retaining their beneficial nutrients. Or, for a cheaper alternative, choose light olive oil. Peanut oil is good for stir-fries. We use coconut oil in baking and some Asian foods.

But olive oil is king. On nonfast days, when you are not worrying about calorie-counting, we would encourage you to be generous with it.

It tastes gorgeous, keeps you full for longer and has health benefits. Don’t worry about the ‘smoke point’ when frying, as olive oil is safe when heated at normal cooking temperatures.

QWhat kind of oils are best?

Do I need to take vitamins?

A We reCOMMeND taking a good- quality multivitamin on 800-calorie fasting days, to make sure you get the vitamins and minerals you need.

Although the menus and recipes in this diet plan are designed to ensure you get all the necessary minerals and vitamins, it’s better to be on the safe side.

QHow much meat should I eat?

A We Are reducing the amount of meat we eat for health and environmental reasons. We have done this by stealth, so the kids haven’t really noticed the change. And we are all thoroughly enjoying our meat-free meals.

however, on a fasting day, eating meat is an effective way to ensure you get enough protein. As for processed meats — eat these only occasionally and choose good-quality products.

Processed meats have been linked in several studies with an increased risk of diseases including cancer and heart disease. It often contains high quantities of nitrates and other chemicals not normally present in fresh meat, and is also high in salt.

QIs it vegetarian or vegan friendly?

A the diet is suitable for vegetarians and vegans, but you need to make sure you are getting enough high- quality protein. so, we recommend adding extra protein where possible, such as nuts or seeds, tofu, edamame, quinoa, lentils or beans — even if this takes you up to 900 calories on fast days — it’s worth it.

Adding high- protein meal replacement shakes can also help — see thefast800.com for veggie-friendly shakes.

Vegans may find it more difficult to get enough protein and nutrients on 800 calories a day. Making a fasting diet suitable for vegans requires careful planning, and is best done with professional support.

We recommend increasing the calories well beyond 800 to ensure adequate protein intake.

QShould I tell my doctor?

A It Is always best to tell health professionals about a major change to your diet, particularly if you have a medical condition and/or are on medication. Most health professionals will be supportive. You can print out a letter advising them about the diet, so they can monitor you. Find this at thefast800.com/healthcareprofessionals. Visit thefast800.com for a full list of medical conditions that may make you unsuitable for this diet.

SAFETY FIRST: The diet is unsuitable for teenagers, if you are breastfeeding, pregnant, frail, unwell, underweight, are undertaking endurance exercise, have an eating disorder, or are undergoing fertility treatment. The Fast 800 Recipe Book by Dr Clare Bailey and Justine Pattison is published by Short Books, £16.99. © Parenting Matters Ltd. To order a copy for £13.60 call 0844 571 0640. P&P is free on orders over £15. Offer valid until June 22, 2019.