After years of being told we must eat three meals a day, fasting is now the accepted way to diet or maintain our weight. And, discovers Victoria Woodhall, going hungry could make you happier and healthier, too.
Imagine a ‘magic bullet’ that would enable you to lose weight where any number of faddy diets had previously failed. A bullet that could ‘reset’ your immune system and reverse the symptoms of numerous age- and lifestyle-related health conditions including arthritis, type 2 diabetes and cardiovascular disease. A bullet that could improve mental clarity, encourage your body’s cells to regenerate, and even slow down the ageing process.
Believe it or not, that magic bullet exists. It is available to nearly all of us, and it is totally free. That bullet is called fasting.
Petronella Ravenshear used to maintain her slim physique and the energy she needed for her PR job by eating only once or twice a day. Before the term had gained traction in wellbeing circles, Petronella – now a renowned nutritionist – was practising intermittent fasting. ‘It just suited me,’ she says. ‘At that time, in 2000, when I trained in nutritional therapy, the advice was to eat five times a day. So I made myself eat breakfast and had snacks between meals. But the more I ate, the hungrier I felt. Sure enough, I put on weight.’
A few years later she came across the Metabolic Balance programme, which advocates a five-hour fast between meals. ‘It worked like a dream – my clients lost weight and enjoyed higher energy levels, improved digestion and sleep,’ she says.
Fast forward another couple of years and the evidence for intermittent fasting was stacking up – and not just for weight loss. ‘Studies were showing that calorie restriction and intermittent fasting enhanced health in a number of ways, including reducing insulin resistance, inflammation and risk factors for cardiovascular disease, plus improving brain function and DNA repair. So I happily went back to eating just once or twice a day.’
After years of being told we should eat at least three meals a day, science has given us permission to fast. As a religious and cultural practice, fasting has been around for centuries. It’s also something our bodies are adapted for, says Dr Françoise Wilhelmi de Toledo, who runs the Buchinger Wilhelmi therapeutic fasting clinics in Spain and Germany.
In order to survive periods of scarcity, our bodies have evolved to switch from ‘external’ nutrition (from food) to ‘internal’ nutrition (from fat reserves). ‘However, we now have a permanent abundance of food and don’t use our fasting mechanisms,’ she says. ‘It’s a pity because so many of us are overweight and have metabolic problems that fasting can help or even eradicate.’ In fact, the latest research demonstrates that important repair processes in the body only happen when we fast.
Fasting has entered the wellbeing lexicon – anyone with a healthy body weight can now skip meals or drastically reduce calories for a time, without necessarily raising red flags about our psychological welfare (fasting is not recommended for those with eating disorders; however there is no evidence that one leads to the other). In fact, periods spent abstaining from food have been shown to make us mentally sharper. ‘People commonly report a heightened sense of clarity when they fast,’ says Petronella. ‘In our caveman days, the feeling of hunger would be equated with danger (ie, of starving to death), so we had to be focused in our search for food.
Fasting increases brain-derived neurotrophic factor (BDNF), a protein that interacts with the neurons that affect memory, learning and higher cognitive function. It promotes the growth of new neurons and the development of synapses, while low levels of BDNF are linked to many conditions including Alzheimer’s, depression and premature ageing.’
Dr Michael Mosley’s bestselling The Fast Diet caught the public imagination in 2013 because the rules were simple – five days of normal eating and two fast days of 500 to 600 calories. Experimenting on himself in the BBC documentary Eat, Fast and Live Longer, Dr Mosley – who was pre-diabetic with high cholesterol – lost 20lb in 12 weeks and his blood sugar and cholesterol levels returned to normal.
A 2011 Manchester University study on overweight women had already shown that following a strict diet for two days a week was more effective than conventional low-calorie dieting: ‘The 5:2 dieters saw improvements in insulin sensitivity; they lost twice as much fat and were much more likely to stick to their diet,’ he says.
The reason why fasting is more powerful than other diets is that we’re not constantly pumping out insulin in response to food. ‘Insulin is not only a fat-storage hormone, but a cell growth accelerator strongly linked with a number of cancers,’ says Dr Mosley.
But it is the type of fat that fasting targets – the visceral fat around the middle – that gives it the advantage over other regimes. ‘Fasting, like exercise, is a stress to the system,’ explains Dr Mosley. ‘It produces adrenalin and growth hormones that target visceral fat.’
And it’s this fat that is associated with a higher risk of health conditions such as type 2 diabetes, heart disease, breast cancer, colorectal cancers and Alzheimer’s.
Nutrition experts agree that, as an entry-level approach to fasting, cutting out snacks is one of the biggest improvements we can make to our health. Leaving several hours between meals encourages fat burning (the hormone glucagon, which tells the body to break down fat, only appears a few hours after eating), is anti-inflammatory and allows our gut microbes to get on with important repair work.
‘One particular microbe, akkermansia, helpfully prunes the lining of the gut, thus strengthening it, but this only happens when we fast,’ explains Petronella. ‘So-called leaky gut allows pro-inflammatory cytokines to enter systemic circulation and, as most of our modern so-called lifestyle diseases including heart disease, depression, allergies and metabolic syndrome have inflammation at their core, this is something we should try to avoid.’
The evidence in favour of fasting means that we are having to let go of nutritional pillars we thought were unassailable. Most recently, breakfast has been knocked off its perch as the most important meal of the day with Professor Terence Kealey’s book Breakfast is a Dangerous Meal.
The clinical biochemist was diagnosed with type 2 diabetes in 2010 and advised to eat three meals a day, starting with breakfast to keep his blood sugar stable. But he noticed that his blood sugar was ‘hazardously’ high after breakfast and set out to challenge the commonly held beliefs such as people who eat breakfast ate less and were less hungry later in the day.
Fellow breakfast-skipper Petronella says many clients are relieved to hear that breakfast is not the be-all and end-all. ‘The first week or so of eating better and less frequently can be hard but soon, although people are eating smaller amounts and less frequently, they are no longer on a blood-sugar rollercoaster and hungry all the time. The 4pm slump becomes a thing of the past. They experience higher energy and better digestion and sleep, as well as improvements to mood and motivation.’
Professor Kealey’s ‘no food before noon’ approach is one of a raft of ‘time-restricted feeding’ fasting styles that involve eating either just one or two meals a day, or eating only within a specific window of time – usually eight hours. Ori Hofmekler’s book The Warrior Diet and Dr Xand van Tulleken’s How to Lose Weight Well both involve eating just an evening meal (the previously overweight Dr Van Tulleken lost six and a half stone by doing this), while the Bodhimaya Method and 8-Hour Diet both deploy the 16:8 (16 hours of fasting with an eight-hour window within which you can eat) approach, popular because it’s relatively simple and won’t compromise your social life.
Daniel O’Shaughnessy, nutritional therapist and co-founder of the Bodhimaya Method, explains: ‘If you eat between noon and 8pm, for example, then fast for 16 hours, the bulk of no eating is done while you are asleep.’ Obviously, you can vary the eight-hour eating window to suit your lifestyle. Fasting researcher Dr Krista Varady of the University of Illinois at Chicago found that ‘time-restricted feeding’ may even produce better biochemical markers than intermittent fasting diets such as the 5:2 and her own ‘alternate-day fasting’ approach.
These extended periods of digestive rest are of interest to longevity scientists because they may improve our healthspan – the number of years we live in good health – as opposed to simple lifespan. If we go without food for long enough – at least 12 hours at a stretch, according to Dr Mosley – it puts the body into a repair state called ‘negative protein balance’ or ‘autophagy’.
‘Your body starts to hoover up all the rubbish,’ he explains. ‘It’s equivalent to taking your car to the garage rather than hammering it down the motorway all the time. It’s the accumulation of debris in your cells that really leads to ageing and age-related diseases. Arthritis, type 2 diabetes and other chronic conditions are linked with the build-up of what I would describe as cellular debris. If you can clear that debris on a fairly regular basis, you are more likely to stay healthy.’
During autophagy, explains Dr Wilhelmi de Toledo: ‘The body’s cells are genetically programmed to switch from full activity to protective mode, where they stop growing so fast and repair themselves.’
Autophagy, she continues, literally means ‘eating yourself’ (after all, there’s nothing else to eat when you fast) and we’re not talking proteins required for cell building, repair and muscle mass. The body is clever, she says; it homes in on the damaged, old proteins from cells, recycling what can be reused and eliminating waste (she likens the process to humans needing firewood – you wouldn’t chop up your front door, but you might use the broken old chair).
‘Research from the University of Southern California [USC] shows that fasting cycles shift stem cells from dormant to an active state where they regenerate tissue. This is why, if you fast on a regular basis, you can regenerate your bodily structures.’ However, this stage can’t be accomplished with a simple overnight fast. It takes around four days of continuous fasting to start, which is why Buchinger Wilhelmi offers fasts of a minimum of four days, with adjustment days either side.
These programmes, taken by more than 5,000 people from all over the world every year, have been shown to benefit and sometimes even cure almost all chronic illnesses apart from tuberculosis, advanced-stage cancer and hyperthyroidism. Autoimmune, inflammatory and pain conditions such as fibromyalgia and migraine also respond well, as do depressive states – the mood-boosting neurotransmitter serotonin is more active during a fast.
Fasting is now being employed alongside cancer treatment. It has been shown to reduce the side effects of chemotherapy, a phenomenon writer Decca Aitkenhead experienced during her treatment for breast cancer in 2015. She had heard about the research by Valter Longo, professor of gerontology and biological sciences at USC, on how fasting for three days before chemo had led to a reduction in side effects in patients.
Having been felled for a week by her first round of chemo, she tried Longo’s approach prior to the second round. When the next chemo was administered, Decca prepared for a ‘toxic onslaught’ but it never came.
Fasting may even turbocharge the efficacy of chemo. Professor Longo’s studies in mice show that it puts healthy cells into protective mode while starving cancer cells, making them more vulnerable to chemo. If this can be shown to be as effective in humans, it will be revolutionary.
‘Science is always looking for the magic bullet,’ says Dr Wilhelmi de Toledo. ‘However, we already have that capability within us. Fasting is a magic shield: it protects healthy cells while the unhealthy ones self-destruct.’
It seems that we have unlearned how to leverage our natural capacity for healing and regeneration. And in the age of abundance, the idea of not eating is scary. ‘We have a natural fear of going without food and we need people to guide us to do it in a safe way,’ says Dr Wilhelmi De Toledo. ‘This is what we have been doing [in our clinics] for the past 60 years.’
Going without food for several days (some people fast at Buchinger for two weeks or longer) in a calm and managed environment is easier than it sounds, if testimony from guests is anything to go by. ‘Three days into a fast, the body adjusts to not eating and people experience a feeling of intense calm and serenity,’ says Dr Wilhelmi de Toledo.
The sympathetic nervous system – our go-go mode – gives way to the restful parasympathetic nervous system, our blood pressure drops, blood sugar stabilises and fat cells release their stores. ‘You become more responsive, you listen more, you have more time – you don’t have to prepare and digest food. It’s a state of introspection where you are more in touch with your intuition.’
With expert supervision needed over several days, regular or annual ‘cyclical fasting’ the way our ancestors did is still only within the reach of those who can afford it (a ten-day stay at Buchinger Wilhelmi costs from 2,440 Euros). A DIY approach is not advised – even at Buchinger, small amounts of food (around 250 calories) are given during fast days, exercise is carefully managed to preserve muscle, counselling and medical staff are always on hand and breaking the fast is supervised carefully.
So what is the alternative? ‘A good practice is to prolong the night fast,’ says Dr Wilhelmi de Toledo. ‘Go according to your hunger and satiety instincts: if you are not hungry in the morning, wait until you are. Most of the time you can go 12 to 14 hours comfortably without eating. During that period, some of the fasting processes will begin and if you do this every day, you’ll get a result that has some of the characteristics of the supervised fast. It’s so simple: eat less.’
The jury is still out on which of the fasting regimes delivers the greatest health benefits – most studies have been done only on mice and some of the diets have no science behind them at all. Dr Mosley is personally pro breakfast and anti eating late, especially if it’s your only meal. ‘The evening is probably the worst time of day to consume all your calories. Your blood sugar and blood fat levels are rising at that time of day, as your body is preparing you for being without food overnight.’ When he ate the same meal at 8am and at 8pm for a TV experiment, his blood sugar levels were raised in the morning, but soared in the evening.
Dr van Tulleken, meanwhile, takes a simpler weight-loss approach. Eating just an evening meal was something he could stick to – it took temptation out of his reach and restricted his calories. ‘It’s difficult to eat more than 900 calories in one meal,’ he says.
There is dispute, too, over what to eat during your fast. Professor Longo advocates a plant-based diet, the Bodhimaya Method revolves around a daily 1:7:2 ratio of carbs to veg to protein and Dr Varady’s book The Every Other Day Diet says you can eat what you like so long as you limit your calories on alternate days.
Dr Mosley acknowledges that not everyone gets on with fasting, and Bodhimaya caution against it for those with adrenal fatigue since fasting produces an adrenal response (it’s also not recommended for children, pregnant women or people with eating disorders, and those with medical conditions should seek advice).
What’s clear is that fasting is a free health resource available to all. However, it’s a challenge in the age of plenty – many of us have forgotten what true hunger feels like – and when there are commercial interests pinned on getting us to eat around the clock.
But remember, it’s OK to feel a little bit hungry – it could even be the very thing that keeps us alive.
● The Fast-Mimicking Diet ProLon is a carefully balanced meal box developed by Valter Longo, professor of gerontology and biological sciences. Used for five days every month, it mimics the effects of a ‘periodic’ fast of three or more days said to enable maximum rejuvenation benefits. prolonfmd.com.
● Bodhimaya Method also incorporates a Friday night to Monday morning fast every three months with only juices and soups and fasting retreats. bodhimaya.com.
● Buchinger Wilhelmi offers ten, 14 and 21 days of medically supervised fasting in a hotel setting. Stays include an initiation phase and at least four days of progressive refeeding. buchinger-wilhelmi.com.
For more on fasting, read Therapeutic Fasting: The Buchinger Amplius Method by Dr Françoise Wilhelmi de Toledo.
Fasting by numbers
5:2, published as The Fast Diet in 2013, is the brainchild of Dr Michael Mosley. It involves five days of normal eating and two ‘fast’ days of now up to 800 calories. Fans include Beyoncé, Benedict Cumberbatch and former chancellor George Osborne.
1:1, published as The Every Other Day Diet by Dr Krista Varady and Bill Gottlieb. Restricts eating to 500 calories every other day. Also called Alternate Day Fasting (ADF).
8-weeks The Blood Sugar Diet by Dr Michael Mosley involves three small meals totalling 800 calories for eight weeks and is aimed at preventing and reversing type 2 diabetes.
6:1 Simple and straightforward, you just go without food for one day a week. Coldplay’s Chris Martin is a fan.
Hugh Jackman favours The 8-Hour Diet. 16:8, published as The 8-Hour Diet by Men’s Health editor David Zinczenko and Peter Moore. Fast for 16 hours and consume all food within an eight-hour window. Advocates include actors Jennifer Love Hewitt and Hugh Jackman.
Olympic swimmer Rebecca Adlington follows The Bodhimaya Method. 16:8 + 1:7:2, aka The Bodhimaya Method. Eat within an eight-hour window and ensure your daily intake corresponds to an optimum nutrition ratio of 1:7:2 – one portion carbs; seven fruit and veg, and two protein. Rebecca Adlington is a fan.
The Warrior Diet by Ori Hofmekler involves only one evening meal, supposedly as our warrior ancestors ate. Actors Joanna Lumley and Nigel Havers attribute their slimness to one meal a day.
Metabolic Balance Programme, founded by Dr Wolf Funfack, is now offered by nutritional therapists around the world. A bespoke three-month programme involving five-hour fasts between meals. Adopters include Sam Smith and Jemma Kidd.
How to Lose Weight Well, Dr Xand van Tulleken’s regime. Eat one 800-calorie meal a day for rapid weight loss and intermittent fasting benefits. Or eat two healthy meals a day totalling 1,200 calories or three meals comprising up to 1,500 calories.