Will you try the new (easy) fast diet?

Most of us don’t have the discipline to fast for two days a week. Now you can lose weight by fasting for only five days a month

Valter Longo first drove into our lives four years ago in a bright red vintage Ferrari convertible. His passenger then was Dr Michael Mosley, who had come to California in search of a scientific way to live longer and defy the effects of ageing — and in the process create a documentary for the BBC’s Horizon: Eat, Fast and Live Longer.

The dark-haired, good-looking Italian chauffeur wasn’t just eye candy. He was the professor of gerontology and biological sciences at the University of Southern California and an eminent figure in the study of the complex mechanics that control ageing and diseases associated with it such as diabetes and cancer.

The car, though, was a gimmick — the 44-year-old professor used it to explain how high levels of a hormone called IGF-1 encouraged the body to burn fuel like a sports car, prompting cells to replicate rather than repair themselves, leading to weight gain, increasing the potential for disease and decreasing life expectancy.

Under Longo’s guidance, Mosley embarked on a three-day fast the results of which were to halve his levels of IGF-1 and reboot his health. Inspired by this, Mosley went on to co-write The Fast Diet, a book credited with popularising intermittent fasting, whereby twice a week you cut your calorie intake to minuscule amounts — the 5:2 diet, the fast diet, call it what you will.

Everyone I know has tried the diet. Its appeal has always been its simplicity: cut your calorie intake to tiny amounts twice a week and you can relieve yourself of dietary starvation the rest of the time. For that my male friends have loved it as much as women do and we have all relished not just the accelerated and sustained weight loss, but the promise of improved health and a longer life.

Yet in practice for some people on-off fasting has taken its toll. Friends tell me they grew tetchy of the relentless weekly cycle — “It made me dizzy and dehydrated,” says one woman I know. It transpires that even Longo, although not critical of 5:2 dieting, could see that continued, intermittent fasting had its shortfalls. “Strict fasting is hard for people to stick to and intermittent fasting with low calories is a lot for people to handle,” Longo tells me when I call him in Los Angeles. “People cheat; they feel it’s too hard.”

Now Longo has come up with a new diet, the “fasting-mimicking diet” (FMD). It is in essence a cheat’s fast, which involves cutting your calorie intake for just five consecutive days a month, but which achieves similar effects to the 5:2.

The diet’s creator, Valter Longo, says that there are shortfalls in strict intermittent fasting

Unusually for a man who promotes denial as a means to healthy living, Longo loves his food. He grew up in Molochio, an Italian town known for the longevity of its inhabitants, on a diet of pasta, vegetables and olives. He says he wouldn’t want to stick to a regimen that was so restrictive it made him miserable. He wants to “enjoy eating normally” as much as he can.

Even the most reluctant dieter can get their head round the rules of FMD: consume 1,100 calories on the first day and 750 calories for the next four and you’re done. For the rest of the month you can eat pretty much what you like. Longo tells me that you could lose up to half a stone in the process. More importantly, his recent research suggests that it could have a dramatic medical impact — it may prove to be a cure for type 2 diabetes, a condition affecting three million people in the UK.

In a trial published in the journal Cell, Longo and his team showed how the five-day diet appeared to “reboot” the bodies of mice with types 1 and 2 diabetes, both of which are characterised by problems regulating blood sugar levels due to difficulties in producing or responding to insulin. “The cycle of fasting meant we were able to demonstrate how non-insulin-producing cells could be regenerated into insulin-producing cells,” he says. Even mice in late stages of the condition saw cells reprogrammed so that they functioned effectively.

Other researchers have shown similar benefits fasting has on the prognosis of type 2 diabetes and, with larger trials planned, the evidence seems ever more convincing. Longo stresses that it’s not without risks: “No diabetes patient should self-administer a fasting diet and it should not be tried even with the help of a doctor since most doctors may not realise that its combination with insulin and other drugs could be very dangerous,” he says. Nevertheless he is confident it has uses for diabetes and other medical issues.

In another trial published last month, Longo and his colleagues randomly divided 100 healthy adults, only a small number of whom had significant weight to lose, into a control group and another that followed FMD. All of the participants underwent a battery of tests, with the five-day fasters showing improvements in a range of metabolic markers linked with ageing and diseases, such as reduced blood sugar levels, cholesterol and blood pressure. Additionally, their levels of IGF-1 and C-reactive protein, a risk factor for cardiovascular disease, had gone down. Longo’s lab is embarking on further trials looking at the effects of the diet on cancer and MS patients and the immune response to the influenza vaccine.

“Over the last 20 years, a tremendous amount of work has shown that, by reducing food intake to trigger a drop in levels of certain hormones, the body responds by regenerating healthy cells and getting rid of damaged or unhealthy ones,” Longo explains. He likens our bodies to steam trains that burn fuel to the very bottom of supplies to enable maximal refueling at the next station. “By emptying our body’s reserves occasionally, we are able to rebuild cells so that they are stronger and better able to withstand disease.”

If you have excess weight to lose, the drop will be greater

For those who are more concerned about their waistlines, the good news is that weight loss was a welcome side-effect on all of Longo’s research programmes, with participants shedding an average of 5.7lb in one to three months. Total body fat, trunk fat, BMI and waist circumference are also significantly reduced on the plan. “If you have excess weight to lose, the drop will be greater,” Longo says. “If you don’t, then it’s more about maintaining weight and improving health.”

Such is his faith in FMD Longo has commercialised the findings in the form of a five-day meal plan to be launched in the UK next month. ProLon — it stands for PROmote Health and LONgevity and not, as I presumed, Professor Longo — will provide daily supplies for a mini fast in a box delivered to your door for about £225. Its combination of soups, crackers, health bars, supplements and energy drinks is formulated with precision to be low in sugar but relatively high in complex carbs and healthy fats.

If you want the specifics, that means 10 per cent protein, 56 per cent fat and 34 per cent carbohydrate on day one, then on days two to five the mix is 9 per cent protein, 44 per cent fat and 47 per cent carbohydrate coming in at about 750 calories. A book is to follow this year and, given Longo’s pedigree, it’s an odds-on bestseller. None of this is likely to make him a millionaire. “I’ve committed all my shares to a nonprofit organisation that I started called Create Cures, so we could continue to research and learn about fasting,” he says.

The format has been tested on almost 4,000 people and Longo says the approach is popular not just because of fat-shredding, but because it’s less risky and hardcore than a full-blown fast. “We still don’t know how safe long-term fasting is,” he says. “We do know that there are some risks, such as gallstones, with frequent fasting of more than 12 hours’ duration, but there may be other side-effects we don’t know about yet.”

For those with 5:2 fatigue, the FMD certainly seems more forgiving. “We are not even saying that people should fast strictly for five days every month,” Longo says. “For a normal-weight person with no health issues, the benefits of a single five-day fast can extend to several months. Repeating the diet every three to four months is enough.” If you are looking to annihilate your body fat, a monthly fast is probably optimal. “But don’t put pressure on yourself to repeat it at a certain time,” Longo says. “If you are on holiday or away with work when you planned to fast, postpone it to the following week. It should not be stressful.”

It strikes me that the diet is eminently doable, more so even than the 5:2. If you managed the pitiful 500 daily calories it permits, then 1,100 or even the 750 allowed on the most extreme days will seem a feast. It’s also deliciously short-term. See it through the five days and you are effectively off-duty for weeks, yet you will still see your dress size dropping. Who could fail to be won over?