Discover how to stay lean and live longer by introducing some easy-to-follow ‘weight loss windows’ to your eating routine.
Perhaps you did it yourself, a friend or family member tried it, or you simply read about it. A couple of years ago there was no ignoring the popularity of 5:2 – the diet where you significantly cut calories for a couple of days a week to reap the benefits of fasting. And while that diet might not be all over the news any more, there’s still plenty of research going on to say that waiting longer between meals – this time for hours rather than a day – is a reliable way to keep you looking and feeling young.
And reducing your eating window – the number of hours in a day during which you consume food – could not only help you slim more quickly, but also increase your brain function, heart health, and resistance to disease. The idea is to give your body a rest from digesting food so it can perform other, longevity-increasing tasks.
What usually draws people to some variation on a fasting diet is the prospect of getting leaner. You could lose up to eight per cent of your body weight in an average of six months, and shave seven per cent off your waist measurement, according to a study from the University of Illinois. But, these slimming gains aren’t just down to giving yourself less time in which to eat and therefore reducing your calories – it’s a whole lot cleverer than that.
‘Increasing the amount of time between meals can induce ketosis,
a metabolic process that encourages you to burn fat stored in your body as its primary energy source, rather than glucose from carbohydrates,’ says Kim Pearson, ambassador for the fasting plan ProLon.
This helps to reduce excess body fat, including the stubborn bit around your belly. While you’re eating this way, it also helps your metabolism. ‘When you restrict how much you eat for a period of time and then follow that with a period of normal eating – i.e. intermittent fasting – you can stimulate your metabolism by as much as 14 per cent,’ says genetic nutritionist Kate Llewellyn-Waters.
What’s more, while you’re having a break from processing food, it releases several hormones that help you to gain energy from your stored body fat. One of these is human growth hormone (HGH) which helps burn body fat and crucially build muscle at the same time. And the more muscle you have, the more calories you naturally use on a day-to-day basis.
Stay younger longer
And there’s even more to be gained from eating windows than just a slimmer silhouette. ‘On fasting days your body uses stored energy from body fat and glycogen (sugar), this obviously aids weight loss, and also improves your blood glucose and cholesterol levels,’ says Kate. ‘Studies have shown that intermittent fasting helps reduce “bad” LDL cholesterol, whilst increasing “good” HDL cholesterol. It also decreases your blood pressure and improves insulin sensitivity, which reduces your risk of
type 2 diabetes.’
The long-term anti-ageing benefits of fasting happen because when your body doesn’t have food to fuel itself, it has to look at what resources it already has at hand to keep you going. ‘It starts to recycle old, faulty and diseased cells, in a process called autophagy,’ says Kim. ‘This makes way for new, healthier cells to grow in their place once you start eating again.’ It’s this process that the experts believe leads to an increase in longevity and a decrease in your risk of developing diseases such as cancer.
Pick your weight-loss window
There are lots of different ways to get the benefits of this idea, each one requiring you to go without food or reduce your calorie intake over a different period of time. Which one you choose depends on the results you’re after, and your lifestyle.
The 12-hour window
This involves you only eating during a 12-hour period in 24 hours – something you might find you’re doing already. For example, if you eat breakfast at 8am, you’ll have your last meal at 8pm – making it ideal if you tend to eat with your partner or family in the evenings. Most people on this plan don’t count calories, but if you want results then eat veg, lean protein and wholegrains. It might not have the longevity benefits of longer periods of fasting, but it’ll keep you trim, and reduce your diabetes risk.
‘One study found that women who didn’t eat or drink anything (other than water) for at least 12 hours had better blood sugar control than women who didn’t fast that long overnight, regardless of how many calories they ate during the day,’ says Kate.
The 16:8 window
If you go without food for 16 hours per day, for example have your last meal at 7pm, then don’t eat until 11am the next day, it can provide quicker weight loss – even if you just do it a few times a week.
Many people find they’re not overly hungry in the morning, especially once they are used to the routine. However, when your body knows food is on the cards again once you break the fast, it often asks for more. Filling up on fibre, protein, and plenty of water can offset this, and you can always work your way from 12:12 to 16:8 over a few weeks.
After 16 hours without food, ketosis really starts to kick in and your body will be burning fat fast. This causes fatty acids called ketones to be released into your bloodstream. These are a great source of energy for your brain, which helps reduce inflammation and reduce your risk of memory problems in later life, according to research by the National Institute on Aging, US.
Light breakfast 11am
Your usual lunch 2pm
Your usual dinner 7pm
Made popular by the 5:2 diet, this plan sees you reducing calorie intake to just 25 per cent (around 500 calories for women and 600 for men) for a couple of non-consecutive days a week. You’ll get the benefits of a longer-term fast without going too hungry. On your non-fast days, eat as you normally would – being careful not to overeat sugary, fatty foods or you could undo your fast-day calorie deficit. On your fast days, you could stick to one main 500-calorie meal in the evening, or spread out the calories. Your body will still be burning stored fat for energy, and autophagy will begin. ‘Periods of fasting like this have been shown to improve life expectancy and decrease your risk of diseases such as Alzheimer’s and cancer,’ says Kate. ‘Fasting for this length of time puts mild stress on your body, but this positive stress encourages it to improve its cellular defences and helps it fight back against molecular damage and repair itself.’
Some experts suggest that to get the full range of health benefits you need to fast for
a few days in a row once a month – something that some cultures have practised for thousands of years. ‘The most significant transformations occur after 48 hours with little food,’ says Kim. ‘This is when your body really starts to break down and replace old cells, reducing your risk of age-related health problems.’
If you want to do a fast like this, ask your GP for advice on how to go about it.
You can now look to your DNA for a personalised fasting plan. The What IF Plan (£229) tests 32 genetic variants that affect how you lose weight, such as your sensitivity to carbs, saturated fat and caffeine, as well as your levels of gluten and lactose intolerance. ‘Eating a genetically appropriate diet could help you lose 287 per cent more weight over 12 months than a non-genetically-appropriate diet,’ says Kate.