Dr Michael Mosley answers 11 key questions to help you succeed at the Fast 800 or 5:2 diet. Good news, it's surprisingly simple

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We know that 90 per cent of diets fail (or should we say dieters) but one science-backed plan that is bucking the trend is the Fast 800 , created by Dr Michael Mosely - himself a former type-2 diabetic who set out to discover the best way for most people to lose weight and keep it off. His channel four show Lose a Stone in 21 Days with Michael Mosley is currently airing on Wednesdays at 9pm.

Combining intermittent fasting 5:2  with time-restricted eating  and the principles of the Mediterranean diet , the Fast 800 is an eating plan that can be tailored to different lifestyles, curbs the urge to snack and allows the odd treat such as red wine and dark chocolate. Most people can report that the meal plans mean they do not make them hungry on fast days .

Dr Michael Mosley to explain why it works by tackling some of the most commonreport does not make them  questions and the dieting myths that can sabotage the best of intentions.

1. It is better to lose weight slowly and steadily, rather than rapidly?

"There is a widespread belief that if you lose weight fast then you will put it on even faster. But is it true? In a review article titled ‘ Myths, Presumptions and Facts about Obesity ’ in the prestigious medical journal, The New England Journal of Medicine, researchers put this claim firmly into the ‘myths’ category.

"After looking at numerous studies which have compared rapid with slow and steady weight loss, they concluded that you would do better to lose it quickly rather than slowly.

"A recent Australian study published in The Lance t backs up these claims. Researchers took 200 obese volunteers and put half of them on a low-calorie diet (less than 800 calories a day) for 12 weeks. The other half were asked to cut their calories by 500 a day, enough to lose around a pound a week. They were asked to do this for 36 weeks.

"There was a very high drop-out rate among the steady dieters: less than half made it to the end of the 36 weeks. Most said they gave up because they were frustrated by the slow rate of progress.

"By comparison, more than 80 per cent of those in the rapid weight loss programme stuck to it.  They were then followed for three years. Although both groups put some weight back on, the amounts were similar.

"Katrina Purcell, a dietician who led the study, said, “Our results show that achieving a weight loss target is more likely and drop-out is lower, if losing weight is done quickly."

Rapid weight loss isn’t suitable for everyone and if you do decide to lose weight fast you have to make sure you have the right balance of nutrients in your diet.

2. Is it advisable to set realistic weight loss targets or goals before you begin a diet?

"This is another of those very popular beliefs which simply isn’t supported by any science. In fact, it’s better to set a big goal rather than say, “I’ll try to lose a few pounds” according to the results from a study called ‘ Weight loss goals and treatment outcomes among overweight men and women

"They asked nearly 2000 overweight men and women about their goals before they started on a weight loss programme. They followed these people for two years and found that women who had ‘less realistic goals’ were the ones who lost the most weight. In other words, it was better to aim high. For men there was no link, one way or the other, between how realistic their goals were and how much weight they lost.

3. Which foods should I eat to feel fuller and stop sweet cravings?

"Have you ever wondered why it is so hard, once you have started eating junk food, to stop? Just as the right foods help you to feel fuller for longer, the wrong foods can do the exact reverse, throwing our brains into a cascade of craving. Abundant, energy-dense, hyper-palatable foods are an incredibly recent arrival in our food environment. In three million years of human evolution, nothing has prepared us for it. In consequence, our brains are completely unequipped to cope with the intense reward that such food delivers, and switch to ‘more-and-more’ mode after the first bite, especially if we take that bite when we are hungry.

"Junk food is trap food, designed to make you lose money and gain pounds. As a guide, the more aggressively it is advertised, the worse it probably is for you. If you want to feel fuller for longer, keep away from it. When you’re out and about, bring a packed lunch; likewise, if you have to keep a stock of high-calorie snacks in the house for children, keep it locked up and away from the kitchen. To feel fuller for longer, then, take a few simple steps – choose more of the right foods – especially good fats and fibre – avoid the wrong foods, eat protein, and eat it early in the day. Like happiness, fullness really is a gut feeling."

Try these delicious power balls  or rhubarb yoghurt dessert  for a healthy snack.

4. Do you need to eat regularly to keep your blood sugars up?

A: "Eating lots of small meals simply feeds your hunger. In the study I mentioned above they also measured the volunteers’ blood sugar levels. Although these levels did fall after three days without any food, they still remained well within the normal range. At the same time, the levels of fat in their blood shot up, showing that their bodies had switched into major fat-burning mode."

Which brings us to…

5. Is it better to eat several small meals a day or a couple of large ones?

A: "A common belief is that if you spread out your food into lots of small meals this will increase your metabolic rate, keep you less hungry and help you lose weight. That’s not true. In a recent study, researchers at the Institute for Clinical and Experimental Medicine in Prague decided to test this idea by feeding two groups meals with the same number of calories but taken as either two or six meals a day. Each group ate around 1,700 calories a day. Despite eating the same number of calories the ‘two meal a day’ group lost, on average, 1.4kg more than the snackers and about 1.5inches more from around their waists. They also felt more satisfied and less hungry than those eating little and often."

MORE GLOSS: 10 meal plan ideas for 5:2 Fast Days

6. Is eating breakfast important if you want to avoid putting on weight?

A: "We are often told that eating a good breakfast is a simple way to control your weight. If you skip breakfast, then you will get hungry later in the day and snack on high-calorie junk food. Eating breakfast revs up your metabolism, preparing you for the day. It seems a plausible suggestion but is it true? To test this idea researchers took 300 overweight volunteers and asked those who normally skip breakfast to eat breakfast, while those who routinely ate breakfast were asked to skip it. They weighed the volunteers beforehand and 16 weeks later.

"So what actually happened? Well, the breakfast skippers who had made themselves eat breakfast lost an average of 0.76kgs. While the breakfast eaters, who had spent 16 weeks skipping breakfast, lost an almost identical amount, an average of 0.71kgs. The researchers concluded that, contrary to what is widely believed, a recommendation to eat breakfast “had no discernible effect on weight loss in free-living adults who were attempting to lose weight”.

MORE GLOSS: Dr Michael Mosley: why a low carb breakfast will help you lose weight

7. Why is eating within a particular time window (time restricted eating) important for weight loss?

A: "Time-restricted eating is very straightforward. You simply ensure that for at least 12 hours within each 24-hour period, you do not consume any calories. Some people prefer to shorten their eating window further to ten or even just eight hours, although recent research by Dr Satchitananda Panda’s team shows that a 12-hour period away from food is enough time to give your body significant benefits.

"Most adults eat for about 15 hours through the day, which does not leave enough time for cell repair pathways to engage to their fullest extent. The long-term health effects of this can be disastrous, loading the body with chronic physiological stress. Time-restricted eating is a simple and manageable step that can put all of this into reverse – and the test results prove it.

"In an early experiment, Dr Panda divided mice into two groups: one that ate food freely around the clock, and one that could also eat freely, but within an eight-hour window only. Both sets of were fed high-calorie, sugary and fatty food.

"His results were astonishing. The mice that had gorged on a sugary, fatty feast had, as expected, put on huge amounts of weight, particularly a dangerous type of abdominal fat called visceral fat. They developed high cholesterol and high blood sugars and showed signs of liver damage.

"However, genetically identical mice, eating the same food but in an eight-hour window, were protected from these changes. They put on far less weight and suffered much less liver damage.

"In one of the first human trials of time-restricted eating, carried out with the help of the University of Surrey, two groups of healthy volunteers ate the same food, but the group on a time-restricted eating plan (eating breakfast 90 minutes later than usual, and dinner 90 minutes earlier each day) replicated the mouse studies. They lost body fat and saw bigger falls in blood sugar levels and cholesterol than the control group."

8. Is juicing a good way to lose weight?

A: "There are juice diets out there promising that you can lose ‘seven lbs in seven days’ and on a pure juicing diet that can certainly happen. But most of that weight loss is going to be water. The reason is that your body keeps a special store of emergency fuel locked up in your muscles and liver in a form called glycogen. This also binds water. When you stop eating your body burns through the glycogen stores, releasing the water. Not surprisingly, once you start eating normally, your body will replenish its water and glycogen stores and much of the weight will come back on."

9. Are low-fat diets the most effective way to shed pounds?

A: “Go on a low-fat diet” has been the advice of dieticians and doctors for the last half-century, despite remarkably little evidence that such regimes are effective.

"The Women’s Health Initiative, for example, was a massive study that began back in 1991. Approximately 48,800 women were randomly allocated to either a low-fat diet or to a control group (‘stick to what you are doing’).

"At the end of eight years those on a low-fat diet were just 0.88 of a pound lighter than the control group and there was no difference in rates of heart disease or cancer. So what should you eat?

"Choose a Mediterranean diet , rich in fruit and vegetables, but also olive oil, nuts and the occasional glass of red wine. It’s a far better way to lose weight and reduce your risk of heart disease than a low-fat diet."

10. Do I need to do lots of exercise to lose weight?

A: "It seems incredibly obvious. Do some exercise, burn some calories, lose weight. But that isn’t what actually happens. Part of the problem is that fat is very energy-dense. You would need to run for about 36 miles to burn off a single pound of fat. The other problem is that people often reward themselves for doing exercise by having a treat. If you run for a mile you will burn about 120 calories; but if you then decide to eat a small bar of chocolate, you will consume 240 calories. There are lots of benefits to be had from doing exercise, but losing weight is unlikely to be one of them. That said, exercise is a great way of stopping you putting weight back on once you’ve lost it.

11. Why is 800 calories per day the magic number for weight loss?

A: "Most rapid weight loss studies are now based on 800 calories a day, which is high enough to be sustainable and give the nutrients you need, and low enough to lead to rapid weight loss and other beneficial health changes.

"You might worry about getting hungry but most people who do the Fast 800 say that within a very short time your hunger passes. Rapid weight loss encourages your body to switch over to fat burning. It also reduces insulin levels, increases growth hormone and boosts levels of a hormone called BDNF in the brain, which helps improve your mood.

"The Fast 800 as a weight loss plan is based on cutting-edge medical research. It works! It’s not so much a diet, as a bespoke weight loss planner, designed to fit around your own needs. It embraces time-restricted eating and the Mediterranean principles of consuming a diet rich in healthy proteins and vegetables and lower in carbs. Healthy fats such as olive oil and nuts are encouraged and the occasional glass of wine or bite of dark chocolate is allowed, so that people eat well, remain sated and don’t feel deprived. It comprises of three 'tracks' or otions and is combined with advice on planning, exercise and mindfulness.

1.   The Very Fast 800, a 12-week very low calorie (800 per day) plan for rapid weight loss

2.   The New 5:2, which counters insulin resistance with regular two-day fasting regimes, where you consumer two meals with a total of 800 calories per day.

3.   The Way of Life, which works either as a great maintenance plan for those who have achieved their goals, or as an entry-level plan for those considering their next options

Life is about much, much more than calorie counting. So why condemn yourself to years of struggling with pointless weight-loss regimes, when a focused and structured intervention can switch your cravings off for life?

The Fast 800 i s an approach to healthy living and weight loss based on the latest scientific research. The Fast 800 online programme has been developed in conjunction with Dr Michael Mosley to offer support and guidance for achieving long-lasting health.