Avocado baked with eggs. Wooden background, fresh parsley, ground pepper.

For years I’ve been told the best way to lose weight and keep it off is to eating a little less and moving more creating a deficit. The “healthy” weight loss being 1-2lb a week. I know this because there isn’t a diet out there that I haven’t tried over the past 50 years! Some worked short term but the weight just insidiously creeps back on!

Now it seems the science of weight loss is changing, and there’s good, strong research from university professors to suggest that eating just 800 calories a day could be the answer. Research conducted by Professor Roy Taylor* of Newcastle University, and Dr Susan Jebb of Oxford University, suggests that this low-calorie approach is a safe and effective means for rapid weight loss and good for many aspects of your mental and physical health.

Avocado baked with eggs. Wooden background, fresh parsley, ground pepper.

The Fast 800 combines all this latest thinking using 800 calories per day, and time restricted eating, for a motivating rapid weight loss. For time restricted eating you start on 12 hours for your overnight fast, eating within a 12 hour window during the day. This fasting time can be extended to 14 or even 16 hours, but that’s pretty tough.

Author and doctor Dr Michael Mosley published the popular 5.2, six years ago. The diet in which you reduce your calorie intake to just 500-600 calories per day on two ‘fasting’ days and eat a Mediterranean diet for the other five. This new Mosley publication (Fast 800 £8.99) slightly increased the calories, to 800, but for 2-12 weeks. As well as the book, a website programme (£99) supports you on this 12-week journey. This gives you the necessary online support, tailoring the recipes to you, and access to a forum of health professionals who offer coaching and advice.

After the initial 800 stage, you can move to the 5:2 stage still eating 800 on two days and a healthy Mediterranean diet, lower-carb, rich in fish, nuts, olive oil, fresh fruit and veg and low in red meat, refined sugar and saturated fat for 5 the rest of the week.

Portobello mushrooms stuffed with mozzarella and cherry tomato

In the final phase, the maintenance period, you’re no longer calorie counting but you continue to follow a Mediterranean diet, upping your wholegrain intake and increasing your activity. Keep an eye on your weight and make quick changes if you weight creeps up. Either cut back a bit, or do a one day 800 fast.

Mosley has dispelled a lot of dieting myths: The idea that your body will go into starvation mode and crash your metabolism (and stop burning fat) is also a “popular myth,” he says. In more recent studies on intermittent fasting, on entering a metabolic chamber the first reaction is that a respondent’s metabolic rate actually goes up.

I’d recommend both the book and the website. The latter, especially if you are looking at the 800 for 12 weeks, as you will need that help and support. Having tried so many diets I think the main thing is choose one that you can maintain and enjoy. I adapted it for the rest of the family, giving them bigger potions and adding healthy carbs i.e. farro, brown rice, quinoa. The recipes are tasty and varied, just smaller! You will also initially have to give up snacks, alcohol and sugary drinks. Always check with your GP first. This diet is not suitable for under-18s, or if you’re breastfeeding, pregnant or undergoing fertility treatment. Nor is it for those who are underweight, have an eating disorder, psychiatric issues, suffered from recent heart problems, uncontrolled heart disease or high blood pressure.

Dr Michael Mosley’s Fast Tour: Michael will be doing his first ever live UK tour in February and March. For details, visit  michaelmosley.co.uk

*Professor Taylor’s 12-week DiRECT (Diabetes Remission Clinical Trial) trial, which was published in the Lancet in December 2017. It involved 298 participants who had been previously diagnosed with Type 2 diabetes, half of whom received standard diabetes care from their GP, the other half of whom followed a diet of 800 calories a day for three to five months. Almost half of patients following the low calorie diet were able to reverse their diabetes. Remission was found to be closely related to weight loss. Over half (57 per cent) of those who lost 10-15kg were able to stop their medication, along with a third (34 per cent) of those who lost 5-10kg. Meanwhile, only 4 per cent of the control group achieved remission.