Dietitian Juliette Kellow explains how to work out the best way to lose weight following the principles of fasting – while taking a healthy approach to eating
until recently, the idea of fasting to lose weight was treated as a ‘fad diet’ (at least by health professionals) and considered something to avoid. But increasingly, dietitians and doctors are recognising that fasting may offer a suitable solution for some people who need to lose weight for the sake of their health.
Dr Michael Mosley is largely credited with bringing the idea of fasting for weight loss to the UK. His first book, The Fast Diet, written with Mimi Spencer, introduced the 5:2 diet in January 2013. Followers would eat normally for five days a week and ‘fast’ (taking in 500-600 calories a day) on two days a week.
Seven years on, as the popularity of fasting has grown, new variations have emerged to suit different lifestyles and preferences. All of these use the principle of controlling calories, so it’s useful to have a bank of calorie-counted, nutritious recipes to call on for your fasting and
non-fasting days. That’s why HFG has put together this collection of dietitian- approved dishes to take the guesswork out of intermittent fasting and help you lose weight effectively and healthily.
Why might fasting work?
The concept isn’t new. Our hunter
gatherer ancestors were probably exposed to lengthy periods when food was in short supply,
stores when it was more plentiful. Ancient philosophers such as Hippocrates and Plato reportedly recommended fasting for health and healing. And, of course, fasting is an important part of some religions. For example, as part of the Muslim faith, believers fast between sunrise and sunset for a month during Ramadan. In more recent years, though, for most
people fasting has been linked with shaping up and slimming down.
Intermittent fasting, in particular, has become hugely popluar.
This is where periods of normal eating are interspersed with short periods of food restriction (and therefore drastic calorie reduction). Advocates of intermittent fasting suggest
that constantly switching calorie intakes prevents changes in our metabolism that cause weight loss
to slow down and even stop – known as hitting a weight-loss plateau.
Is it backed by science?
A 2015 review of research concluded there was no evidence to support this view. And a 2017 study confirmed that intermittent fasting didn’t stop our metabolic rate falling or our muscle mass decreasing (both things that
IS INTERMITTENT FASTING THE RIGHT CHOICE FOR EVERYONE?
- You like the idea of a part-time diet, where sometimes you restrict your intake, but at other times you’re able to eat normally.
- You have an ‘all or nothing’ approach to dieting. Since you only restrict your intake for short periods, you’re more likely to have the willpower to sustain your fast and are less likely to fall off the wagon.
- You find it difficult to stick to diets because you lack time to think about what to eat, or find diets interfere with your lifestyle.
- You get bored with the day-m, day-out monotony of most diets.
- You’re permanently hungry when you’re trying to lose weight. Intermittent fasting means you’ll only be hungry for short periods.
SEEK ADVICE FROM YOUR DOCTOR BEFORE STARTING IF…
- You have an underlying major health problem.
- You’re taking any medication. This is very important as severely restricting food intake may affect the absorption of some medicines.
- You have type 2 diabetes and are on medication or take insulin. This is essential as your healthcare team will need to provide you with specialist support to prevent potentially dangerous hypos.
YOU SHOULD AVOID INTERMITTENT FASTING IF…
- You’re currently pregnant, breastfeeding or undergoing fertility treatment.
- You’re a child or a teenager.
- You have a history of, or currently have, an eating disorder.
- You’re depressed or suffer with other psychiatric conditions.
- You’re unwell, frail or recovering from surgery.
typically occur when we diet) any more than other calorie-restricted diets.
However, that’s not to say intermittent fasting hasn’t been shown to result in weight loss. In 2017, the British Dietetic Association (BDA) Obesity Specialist Group came to the overall conclusion that intermittent fasting was as effective at helping adults – including those with type 2 diabetes – to lose weight as more traditional diets that restrict calories every day. The reason? Quite simply, it creates an overall calorie shortfall or deficit. Contrary to what many assumed would happen, people don’t tend to follow fasting days with feasting days that undo all the good work.
Champions of this type of diet, such as Michael Mosley, also suggest that intermittent fasting may offer advantages over other forms of dieting as it helps us burn fat more efficiently. When we fast, the first thing our body does is turn to its carbohydrate stores
(the glycogen in muscles and liver) for energy. When these stores are depleted, usually 10-12 hours after eating, our body switches to burning fat for energy.
As fat is broken down it produces ketones, which the brain uses for fuel, a state known as ketosis (this is the same theory used to promote low-carb diets, including Atkins and Keto).
In simple terms, when we eat regularly, we replenish our carbohydrate stores before our body has a chance to burn fat; if we’re fasting, once our carb supplies are used up, our body switches over to burning fat.
What the obesity experts say
Does this mean intermittent fasting results in faster or greater weight loss, or helps us lose more body fat than other diets? Well, we don’t yet know. There’s not enough good-quality research in this area. Certainly, some studies have shown bigger reductions in body fat and a trend towards greater weight loss, but as trials have generally only included a small number of adults, it’s impossible to draw any firm conclusions. For now, the BDA Obesity Specialist Group says the evidence suggests intermittent fasting may be as effective as other diets for weight loss.
What it comes down to is personal preference. Like all diet plans, it may offer a good solution for some people, but it’s not for everyone. If you have a lot of weight to lose and are looking for a diet that will offer you long-term results, we would always recommend
seeking personal advice from a health professional.
Is fasting good for our general health?
Much research has
focused on how fasting might increase lifespan and combat the effects of ageing. However, most of these studies have involved animals rather than humans, again making it difficult to draw any firm conclusions. There have been human studies, though, that have shown that intermittent fasting may help
reduce inflammation and improve conditions such as raised blood glucose, blood pressure and blood cholesterol, all of which are major risk factors for conditions that cut lives short. And there’s increasing evidence that intermittent
fasting may benefit those with signs of developing, or already suffering from, type 2 diabetes, as it improves insulin sensitivity, which in turn helps to
improve blood sugar control.
Potentially good news for your brain – and your gut
Intermittent fasting has also been linked to better cognitive function and protecting against dementia and
Alzheimer’s disease, although, once again, research is largely limited to lab-based studies involving animals.
In these, fasting seems to shock the brain into making new nerve cells and strengthening connections between them. Whether this also happens in people is harder to ascertain.
The latest research (again mostly involving animals) is looking at the impact intermittent fasting may have on gut health, where it seems to help boost the diversity of gut bacteria. In particular, time-restricted or overnight fasting (see p10) seems to have the biggest impact on changes in gut bacteria.
This is because our gut bacteria have a circadian rhythm and are affected by day and night body patterns. An overnight fast seems to help re-establish disrupted circadian rhythms, improving gut health and, therefore, overall health.
TIPS FOR FAST DAYS
- Eat foods that are high in fibre to help fill you up. Vegetables are great choices as they’re also low in calories
- Include protein-rich foods such as white fish, canned tuna in water, shellfish (such as prawns and mussels), chicken and turkey breast ean beef, egg whites, beans and chickpeas. Protein is satiating, so it will help keep hunger at bay for longer
- Choose foods that need a lot of chewing the longer food is in your mouth, the more satisfied you’ll feel
- Eat foods that give you big quantities for few calories – try lettuce, salad leaves, cucumber, celery, radishes, cauliflower, broccoli, kale, spinach, hom em ade vegetable soups, melon, raspberries and strawberries.
- Dilute sugar-free squash with sparkling water and freeze it in lolly moulds for a virtually calorie-free treat when you fancy one.
- Drink calorie-free drinks Water is, of course, the top choice, but you could also add sugar-free squash to it or have sugar-free fizzy drinks. Black tea anc coffee, and fruit and herbal teas are all fine.
W hat’s on the menu on a fasting day?
It’s important to choose a version that fits your lifestyle. Whichever style of intermittent fasting you want to try, you can mix and match the recipes in this collection to add up to the number of calories you’re aiming to have on any given day.
You eat normally (but healthily) for five days a week and fast on two days a week, eating around 500 or 600 calories. How these calories should be split (for example, into two or three meals), and whether you should fast for two consecutive days or separate them out, can vary.
IS IT FOR YOU?
Essentially, this is part-time dieting. Restricting food for just two days a week seems manageable to many. Prepare to feel hungry on fast days, though, as you’ll go for 36 hours on just 500-600 calories.
(If your last ‘normal’ meal is at 7pm on Sunday, you fast on Monday and don’t return to eating normally until 7am on Tuesday.) However, knowing you can eat the next day may see you through.
This involves one day of eating normally followed by one day of fasting, repeated over and over. Plans vary, but some recommend having around 500 calories on fasting days.
IS IT FOR YOU?
his is a stricter version of the 5:2 plan, with more fast days during the week. It may work better if you prefer a set plan and want faster results. But, because you spend more days fasting, you’re more likely to be short on nutrients and will spend more time feeling hungry. Because it’s quite extreme, you may find it harder to stick with.
This is a 24-hour fast. You eat just one meal a day – for example, dinner. One popular version is the Eat- Stop-Eat diet, which recommends whole- day fasting once or twice a week.
IS IT FOR YOU?
This works to significantly restrict calories because it’s difficult (although not impossible) to pack a full day’s worth of calories into just one meal, so you end up with a large calorie deficit. You’ll need to be prepared to feel hungry during the day.
You restrict eating to a set period of time each day and then fast for the remainder of the day. In the 16:8 diet, for example, you limit eating to an eight-hour window and fast for 16 hours, once or twice a week.
IS IT FOR YOU?
Most people trying this type of fasting will end up eating smaller portions or fewer meals. The real advantage of this style of fasting is flexibility – you can plan your eight hours of eating to fit around work, social activities and family life. It’s a good option if you haven’t seen results with overnight fasting (see right).
As the name implies, this means you avoid eating for 12 hours overnight and do most of your fasting while you’re asleep.
IS IT FOR YOU?
This is one of the easiest ways to fast, and is especially good for those used to snacking or drinking in the evening after eating dinner. A large glass of wine and a packet of crisps can have 400 calories, so this plan can be a great way to cut out unnecessary and often nutrient-poor calories. If you tend not to snack in the evening, however, it probably won’t make much different to your normal eating habits.
AND ONE TO AVOID…
Spontaneous fasting involves simply missing a meal if you’re not that hungry or don’t have time to cook or eat. We wouldn’t recommend this approach as it’s not part of a structured plan. Skipping meals in an unplanned way can leave us unprepared for the resulting hunger, so we’re more likely to grab the first thing to hand – and, of course, that won’t necessarily be a healthy choice.
A diet that includes intermittent fasting
Dr Michael Mosley’s latest book, The Fast 800, gives an example of how intermittent fasting works in practice. It’s divided into three stages:
- STAGE 1
A rapid weight-loss phase lasting two to 12 weeks depending on how much weight you need to lose.
You have just 800 calories a day and, preferably, a 12-hour overnight fast each day. It’s essentially a low-carb diet.
- STAGE 2
Basically the 5:2 diet (see far left), with a Med-style diet on non-fasting days.
However, you have 800 calories instead of 500-600 on fasting days and you increase your overnight fast from 12 to 14 hours.
- STAGE 3 This stage is about achieving weight maintenance by following a Med style diet. You will continue with a 12-14 hour overnight fast and stick to just 800 calories one day a week, if needed.
Taking a balanced view
Intermittent fasting can be an effective way to lose weight for some people, but it’s worth remembering it’s not a magic bullet for shifting those pounds. If you struggle to function well when you’re hungry, the chances are intermittent fasting won’t suit you. But if the idea of a ‘part-time’ weight-loss plan appeals, it may be worth giving it a go.
Remember, too, that intermittent fasting doesn’t give better results than weight-loss plans that focus on a more moderate daily calorie restriction – it’s simply a different way to reduce your calorie intake below your needs over a period of time so that your body turns to using its fat stores for energy.
For example, with the 5:2 diet, in a week you have five days of 1,900 calories and two days of 500 calories, which adds up to 10,500 calories. With a more traditional weight-loss plan that allows 1,500 calories a day, you’ll also have 10,500 calories over the course of the week. The restricted calorie
intake is the same – it’s just achieved differently! Both result in a calorie deficit that should allow for a loss of around 1 lb a week.
It’s also important to remember that your intake of nutrients – protein, fibre, vitamins and minerals, for example – may be low on days when you’re fasting. As a rule, the more restricted your diet, the lower your nutrient intake. This means it’s vital to make sure you choose nutrient-packed foods on both fasting and non-fasting days.
However you choose to control your calorie intake, the recipes in this Essential Guide will help you plan healthier menus. As always, our advice is to lose weight with a healthy, balanced diet and a moderate calorie restriction. Many people find intermittent fasting offers a kickstart for achieving this.
If you’re unsure whether it’s for you, consider discussing it with a health professional for advice.
HOWTO STICK TO IT
Adopt a few strategies to help you su cceed .. .
- Be realistic fasting isn’t a magic diet – you’ll still neec willpower and commitment.
- Expect to feel hungry some of the time The gooc news is it won’t be all the time.
- Understand you need to eat healthily around fasting days You can’t follow fasting days with feasting days. Reassuringly, some studies have shown people eat 20% fewer calories than they usee to on non-fasting days.
- Take a vitamin and mineral supplement as a safeguard, as fasting limits nutrients as wel as calories.
- Only weigh yourself once a week That way, you’ll see an overall downward trend rather than the daily fluctuations that occur with fasting.
- Keep exercise gentle on fasting days A brisk walk, for instance, rather than a gym visit.
- Limit exposure to food on fasting days These are not the days to do the weekly food shop or eat out with friends!
- Enlist the help of medical professionals especially if you have type 2 diabetes. A registered dietitian can monitor progress and help ensure your diet is nutritionally balanced.