Life Health & Wellbeing

Sunday 20 January 2019

The fast way to lose weight, live healthily and fight ageing

Intermittent fasting has become a worldwide phenomenon since Dr Michael Mosley expounded on the 5:2 diet in a book and a TV series. Here he explains how calorie restrictions on just a couple of days a week can bring health benefits and also focuses on a Dublin group's experiences when combining the diet plan with short bursts of high-intensity exercise.

All these people have embraced the 5:2 diet. Only Ireland tested it - and it works!
All these people have embraced the 5:2 diet. Only Ireland tested it - and it works!
Dr Michael Mosley
Liv Tyler

Dr Michael Mosley

A patient came into my wife's clinic the other day (my wife is a doctor) and dramatically announced, "my husband's beating me". Fearing the worst, my wife asked the woman what was going on. "We've both been doing the 5:2 diet. I've lost 13 lbs (6 kgs) but he's beating me; he's lost 22 lbs (10kgs)".

It's been two years since I made a documentary called Eat, Fast, Live Longer for the BBC, which I followed up with a book, The Fast Diet. Together they made intermittent fasting into a worldwide phenomenon.

I've been astonished by how well it has gone down, not just with the general public but with doctors. Many medics are not only doing it themselves but also recommending it to their patients. Some have initiated their own studies.

A research group in Stockholm, for example, is halfway through a study following 40 Type 2 diabetics on the 5:2 diet, while a group in Dublin (see pages 6, 16 & 17) has recently created and tested a novel 12-week programme, iFAST, which combines 5:2 dieting with a High Intensity Training (HIT) programme

So what is intermittent fasting?

Scientists call it "intermittent fasting", but it's not fasting in the sense of going without food altogether. A more accurate description would be "intermittent calorie restriction", because what you are doing is cutting back on your calories a few days a week.

Simple though this sounds, there is mounting evidence that intermittent fasting not only leads to steady weight loss but also triggers a cascade of changes within the body that can reduce your risk of a range of diseases. A recent review article published in the scientific journal Cell Metabolism, "Fasting: Molecular Mechanisms and Clinical Applications", found extensive evidence that short periods of fasting reduces many of the things that encourage ageing ("oxidative damage and inflammation") while increasing the body's ability to protect and repair itself.

The article concluded that fasting "helps reduce obesity, hypertension, asthma, and rheumatoid arthritis. Thus, fasting has the potential to delay ageing and help prevent and treat diseases"

Although there are many different types of intermittent fasting, 5:2, a term I use to describe my own approach (cutting your calories for two days a week down to 500 calories for women, 600 for men) is the one that people seem to find easiest to do.

While doing 5:2 I personally lost 9 kgs of fat and managed to reverse my borderline diabetes. The TV presenter, Phillip Schofield, told me that it had become a way of life for him.

It's a diet that has been embraced by celebrities like Beyonce and Benedict Cumberbatch ("you have to, for Sherlock"), Liv Tyler, Ben Affleck and Christy Turlington. The UK Chancellor of the Exchequer, George Osborne, is a fan, as is SNP leader, Alex Salmond , who has lost 3 stone on it and attributes his extra campaigning energy to the diet.

So why does it work?

I think one reason why the Fast Diet has been so successful is because you aren't on a constant treadmill, dieting all the time. As One Foot in the Grave star Richard Wilson, who lost 12lbs (5 kgs) in just five weeks, told a newspaper, "The great thing is that the fasting days are tough but you know that the next day you can eat."

I certainly find it easier to resist the temptation to eat chocolate by saying to myself, "I will have it tomorrow". Then tomorrow comes and maybe I eat it. But sometimes I don't.

Intermittent fasting also teaches you better ways of eating. If you follow recipes in the Fast Diet Recipe Book and satisfy your hunger on fasting days by eating vegetables and good protein, then over time you'll discover that when you get hungry you are more likely to crave the healthy stuff. There is also good evidence that intermittent fasting shrinks the stomach, meaning you are less likely to want to gorge on your non-fast days.

Another reason it works is because it is, at least initially, quite challenging. When we are stressed, at a cellular level, hundreds of protective genes spring into action.

Going without food for short periods of time also switches on a process called autophagy, allowing the body to clear out old damaged cells, making way for new ones.

A few months ago, Professor Valter Longo of the University of Southern California's Longevity Institute discovered that short periods of fasting can boost the body's immune system, leading to the creation of new, more active, white cells. "We could not have predicted," he said, "that fasting would have such a remarkable effect."

Recent scientific studies have not only highlighted the benefits of intermittent fasting, they have also debunked some long-standing dieting myths. These are a couple of the more persistent ones:

Myth. When you stop eating your metabolic rate slows down as your body tries to conserve your fat stores

Many people fear that if they fast they will go into "Starvation mode". This myth seems to be based on the Minnesota starvation experiment, a study carried out during World War Two in which young volunteers lived on extremely low-calorie diets for up to six months. The purpose of the study was to help scientists understand how to treat victims of mass starvation in Europe.

After prolonged starvation there was a drop in body temperature and heart rate, suggesting that their basal metabolic rate (the energy burnt by your body when you are at rest) had fallen. This, however, was an extreme situation.

A more recent experiment on the effects of short term calorie restriction, "Resting energy expenditure in short-term starvation", published in the American Journal of Clinical Nutrition, produced very different results.

In this study, done at the University of Vienna, they took 11 healthy volunteers and asked them to live on nothing but water for 84 hours (four days). The researchers then measured the volunteers' metabolic rate at the end of days one, two, three and four. What they found is that the volunteer's metabolic rate actually went up. After four days without food it was 12pc higher than it had been at the beginning.

One reason for this may have been the significant rise in a catecholamine called noradrenaline, which is known to burn fat.

If they had continued the experiment then, I'm sure, the volunteers' metabolic rates would eventually have fallen, not least because they would have begun to lose significant amounts of weight. But, certainly in the short term, there is no evidence that starvation mode exists.

When you think of it from an evolutionary perspective, "starvation mode" makes little sense. Our remote ancestors often had to go without food for a longish periods of time and if, every time this happened, they had become less active and waited for pizza to be delivered they would have gone extinct. Only during periods of prolonged famine would it make sense to slow the metabolism down, wait for better times to come.

Myth. If you stop eating for a while then your blood sugar will fall dramatically and you will faint

In the trial I mentioned above, they also measured the volunteers' blood glucose levels. They found that their blood glucose levels did slowly fall over the three days, from 4.9mmols/l on day one to 3.5mmols/l by day four. These, however, are the sort of levels you might expect to see in a healthy individual who had their blood taken before breakfast. They are not, in any sense, abnormally low.

At the same time the levels of fatty acids in their blood shot up, showing that their bodies had switched into major fat-burning mode.

Your body evolves to cope for periods without food. Intermittent fasting can be tough, but there is no evidence it is will cause you to faint.

Another claim I've heard from dieticians who should know better is that intermittent fasting lead to muscle breakdown and protein deficiency. If your protein intake is adequate, and we actually recommend an increased protein intake on fasting days, then you are not going to get "muscle protein breakdown". In fact the evidence from human studies points towards intermittent fasting being better than standard diets when it comes to muscle preservation

Myth. It's best to eat lots of small meals a day

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. Researchers at the Institute for Clinical and Experimental Medicine in Prague decided to test this idea by feeding two groups of Type 2 diabetics meals with the same number of calories (1700 a day) but taken as either two or six meals.

The group eating two meals a day ate their first meal in the morning and their next meal between 12pm and 4pm. The others ate at regular intervals throughout the day.

Despite eating the same number of calories the "two meal a day" group lost 1.4kg more than the snackers, and 4 cms more from around their waists.

The volunteers eating their 1700 calories spread out as six meals a day also felt less satisfied and hungrier than those sticking to the two meals.

How to make intermittent fasting work for you

These are a few of my tips for making the fasting days more successful

1 Drink plenty of water, black tea, peppermint tea, coffee. People sometimes confuse thirst with hunger, so you can end up eating lots of extra calories when what all you really need is fluid. A hot drink on an empty stomach is also remarkably soothing.

On fasting days, you will need extra fluid because we get a lot of water from food. Your body will also be burning its way through its glycogen stores, and as it does so you will also be losing the water that binds to the glycogen. If you don't drink enough fluid then you may well develop headaches and constipation.

How much is "enough"? The magic figure that is often quoted is two litres or eight cups of water a day. This is something of a myth and probably dates back to the 1940s when researchers calculated that this was how much water someone's body used in 24 hours. However, the researchers also said (and this gets ignored) that drinks such as coffee and tea also count, despite what many people believe.

Drinking eight glasses of cold water a day will also help you burn calories because your body will use about 70 calories raising it to body temperature.

2 Drink more soup. Drinking water has very little effect on how hungry you feel a couple of hours later, but it can help you lose weight if it comes in the form of soup.

If you drink water with your meal then the food itself will be kept in your stomach for your digestive juice to do their bit, while the water passes straight through the stomach and into the intestines, where it is absorbed.

If you take that same food and blend it with the water then the stomach will stay fuller for longer, staving off hunger pangs.

In head-to-head comparison studies, volunteers eating soup reported feeling full for up to an hour-and-a-half longer than when they ate the same calories, but consumed as food and water.

3 Keep an eye on the amount of calories that you are drinking. Smoothies have a reputation for being healthy because they are based on fruit, but unfortunately by the time you get rid of the fibre and the peel you have lost many of the potential health benefits.

You are left instead with a lot of calories (well over 200 calories in a small bottle) as well as a big sugar hit. In a survey published last year, researchers revealed that out of 52 commercial smoothies, 41 had more sugar than cola and all had more calories. They are also acidic and the bits cling to your teeth, so dentists are not keen. An apple a day may keep the doctor away, but not when it's peeled, blended, mashed and packaged.

The same, sadly, is true of fruit juice. You can drink a lot of fruit juice, at over 100 calories a glass, and it will have no impact on how much you eat at your next meal. I rarely drink it and never have it in the house.

Alcohol is another way of consuming a lot of calories without noticing. A large (175ml) glass of red wine contains about 120 calories, while a pint of Guinness clocks in at around 170.

I have no intention of giving up entirely, but a couple of days a week without an alcoholic drink is good for your health as well as your waist.

4 Empty all the junk food out of your house. Getting rid of temptation means you are far less likely to cheat on fast days, but also that you are less likely to indulge in mindless eating on other days. Unfortunately will-power is grossly over-rated and if you know the treats are close at hand you will almost certainly eat them. I do.

A particularly difficult moment is at the end of the day, when you are relaxing. If you sit down in front of the television with a tub of ice cream or a packet of biscuits anywhere nearby you will probably scoff them without even noticing.

We are particularly prone to eating mindlessly when we are in front of a screen. In one study, where they provided cinema-goers with a big box of popcorn, the popcorn was eaten despite the fact that it was stale. When volunteers were offered the same popcorn outside the cinema they rejected it on the grounds that it "tasted disgusting".

Another trick which is surprisingly effective is to use smaller plates. This helps the portions look larger, but also means you are less likely to go on eating once you are full, simply because you feel you should finish what is on your plate.

5 Don't give up all treats. One of the things you have to be wary of is being in a constant state of self-denial. It is fatal to declare too many foods "off limits", as this often leads to guilty, rebound overeating. I try to limit my consumption of chocolate by buying small amounts (if I buy a big bar, I will eat the whole thing, whatever my original intentions) and by making sure I walk to the shops, which are a mile away, when the compulsion is strong.

If I have to snack (and some days I do) I try to snack on things like fruit or carrots. I also find high protein snacks like nuts or a small bit of cheese satisfying. Nuts are really good for the heart, but I have to buy packets of nuts that I only want to eat a small amount of, such as almonds or walnuts. If I buy salted peanuts, I can easily eat the whole pack.

6 Make sure you fill up on protein and vegetables on your fasting days. Protein is very satiating and you can eat a lot of vegetables for very few calories. There are lots of recipes in The Fast Diet Recipe book and my website, has a friendly forum where people offer help and support.

7 Become more active. Many of us spend up to 12 hours a day sitting on our well-padded bottoms looking at computer screens or watching television. Prolonged sitting not only contributes to obesity but leads to a sharp reduction in the activity of an enzyme called lipoprotein lipase which breaks down fat. This reduction in enzyme activity leads to raised levels of triglycerides and fats in the blood, increasing the risk of heart disease. Extended sitting has also been shown to cause sharp spikes in blood sugar levels after meals, creating the perfect setting for Type 2 diabetes. So if you do spend a lot of your work life sitting down, find an excuse to get up and move - every 30 minutes.

Fast Exercise

If you want to live a long and healthy life, then as well as being more active you also need to do exercise that pushes up your heart rate, creates a bit of stress. The trouble is that few of us are prepared to do the 150 minutes per week of moderate exercise that is routinely recommended.

That is why, a while ago, I began looking into a radically different approach to exercise called HIT, High Intensity Training. The idea is that you can get many of the important benefits of exercise from a few minutes of HIT a week.

Jamie Timmons, Professor of Precision Medicine at Kings College, University of London, is one of the world's leading experts on HIT.

When we first met he assured me that just three minutes of HIT a week improves the body's ability to cope with sugar surges (metabolic fitness), and how good the heart and lungs are at getting oxygen into the body (your aerobic fitness). Nobody really knows why, but these two measures are great predictors of future health.

The version I do is very simple. I get on an exercise bike, warm up by doing gentle cycling for a couple of minutes, then pick up the pace. At the same time I increase the resistance on the bike, pushing the dial to one of the highest levels, so I'm going flat out against almost maximal resistance for 20 seconds.

I then cycle gently for a couple of minutes, long enough to catch my breath, then do another 20 seconds at full throttle. Another couple of minutes gentle cycling, then a final 20 seconds going hell for leather. And that's it.

I do three sessions of HIT a week, plus a simple strength and flexibility regime (you can find out more from my book, "Fast Exercise" or get a free Fast Exercise app from the App Store).

Is it safe?

If you are frail or extremely unfit it would be wise to have a medical check up before starting any form of exercise, but don't use that as an excuse not to start. The benefits greatly outweigh the risks. You can do HIT by yourself, but studies show it is likely to be more effective if you are supervised and do a tailored programme.

©Michael Mosley

The recipe for weight loss



Mackerel fillets

Smoked salmon

Half-fat hummus, low-fat yoghurt, half-fat crème fraiche

Feta, cottage cheese and low-fat mozzarella

Spring onions


Fresh herbs

Non-starchy veggies: cauliflower, broccoli, peppers, radishes, cherry tomatoes, celery, cucumber, mushrooms, lettuce, sugar snaps, mange touts, salad leaves, young spinach, carrots

Fruit: Lemons, strawberries, blueberries, apples


Tinned tuna in spring water

Tins of beans - cannellini, borlotti, flageolet - and chickpeas

Cherry tomatoes

Tomato puree


Onions - red and white

Mustard - Dijon and English

Vinegar - balsamic and white wine; try balsamic spritzer on salad

Olive oil

Cooking oil spray

Spices, including cumin and coriander

Chilli flakes

Nuts - unsalted are preferable; eat with caution as they are generally high in calories

Pickles - guindilla, jalapenos, cornichons, capers

Marmite, Oxo cubes, stock cubes, miso paste

Sea salt and freshly ground black pepper

No-sugar Alpen

No-sugar jelly

Shirataki noodles


Root ginger - it is best grated from frozen

Stock - in empty (clean) soup and milk cartons

Soup - home-made or shop bought, in single portions

Blueberries (strawberries don't freeze well)



Breakfast. If in doubt, eat an egg. A two-egg chilli and spring onion omelette has 180 calories; scrambled eggs with 80g smoked salmon has 300. If you need carbs to start the day, go for porridge - perhaps with chopped pear and cinnamon (286 calories)

Supper. Max out the veg and minimise the carbs. You need protein too; white fish, shellfish and chicken are best. Add flavour rather than calories with lemon, cumin, chilli, lime, ginger, onion…You can have curry, but if you're short of calories, go for fish or prawns instead of meat. Dahl is an ideal choice.

Takeaways. Sashimi boxes are great for a hit of protein (avoid sushi rice). Soup is good too - but go for clear, veg-laden broths, not the heavier, meaty, cheesy alternatives.

Snacks. Not really part of the plan. But if you must, have a handful of almonds, or strawberries, blackberries, or an apple. Include the calorie count in your quota. Also liquorice root to chew, sugar-free jelly pots, cherries, 1 tbsp hummus, 25g Edam, 1 hardboiled egg, 2 hardboiled quail's eggs, 1 tbsp cottage cheese, miso soup sachet, handful frozen grapes, carrot sticks, celery sticks, cherry tomatoes, raw pepper, radishes.

Drinking. Stay hydrated. Alcohol is 'empty' calories (a 550ml beer racks up 250). If you must, vodka has the fewest calories; soda and lemon juice are the best mixers.

Sample menus for under 500 cals.

Breakfast: Poached egg and ham, 170 cals. Supper: Sticky salmon with ginger, 335.

Breakfast: Yoghurt, berries, almonds, 264 cals. Supper: Tuscan bean soup, 178.

Breakfast: Poached eggs, 180 cals. Supper: Aubergine curry and brown basmati rice, 250.

Breakfast: Two boiled eggs, asparagus, 180 cals. Supper: Gazpacho, 113, courgette, pea and ricotta salad, 181.

Adapted from Fast Cook, Delicious low-calorie recipes to get you through your Fast Days by Mimi Spencer (Short Books €14.30)


Sunday Independent

Editors Choice

Also in Life