I am a huge fan of intermittent fasting, I’ve even co-written a book on it, so I just might be a little biased (!) but I do pride myself on being balanced, measured and evidence based. I’m also curious, sceptical and just sometimes a little painful. I’m the annoying child in the class who is always asking ‘but why’?!
My job is to review the evidence so any nutritional advice I give is impartial and firmly based on research and scientific reviews. With intermittent fasting there’s an increasing body of research to demonstrate that it is not only effective for weight loss, but also for our long term health. This is in stark contrast to many other diets which may be effective for fast initial weight loss, but certainly not sustainable or even good for us in the longer term.
So what is intermittent fasting?
The key word is ‘intermittent’ or not eating all the time! Quite simply having longer periods between meals means that once the body has used up its immediate energy supply, it has to then move onto burning its fat stores. Think of it like this: constantly grazing means that you never run your fuel ‘tank’ on empty and for weight loss you actually need to refill your ‘tank’ from your body stores, not from food.
Once the body has used up its immediate energy supply, it has to move onto burning its fat stores
Ah – but you’ve heard that you need to eat little and often to maintain your energy levels and burn calories? This theory has now been thoroughly disproved (unless you are a child, an elderly person or a rabbit!). The average healthy adult does not need to be constantly eating.
There are different ways of doing it. You may have heard of the ‘16/8’ or variations on this whereby people skip at least one meal, in order to have a longer period of time without eating.
For example, if you eat your supper by 8 pm and then skip breakfast, not eating until 12 noon the next day, this is a 16-hour period without food (hence the 16 hours) while you eat within an 8 window, with lunch at 12 and supper by 8 pm (hence the 8).
The other intermittent diet is the 5/2; eating normally 5 days a week and having 2 days a week where you don’t eat much, around 25% of your normal daily calorie intake.
Why is it effective for weight loss?
Whether it’s the 16/8 method, the 5/2 method or some other variation, you are eating less which (in theory) results in weight loss. But where intermittent fasting seems to have the edge, is that it seems to burn more fat while maintaining muscle mass. When dieting the aim should be to lose fat while preserving as much muscle mass as possible. As to how the body manages this (and I was hoping you’d ask that question!), the longer time periods without eating mean the body simply has to dig into its fat reserves.
A further advantage of this approach is that it seems to help people manage their appetite better in the longer term. You can get used to feeling hungry and rather than panicking about it, learn to wait it out until the next meal. Of course, it can also backfire, getting so hungry that you binge or eat too much when you refuel. The aim should be to eat normally at the next meal, not stuff your face! This sometimes takes practise……!
Other positive points about the intermittent fasting approach? It’s flexible, so that a) we don’t feel we are on a constant diet and b) can fit the diet into our lifestyles relatively easily, we can choose the days where we skip or reduce our food intake according to our social and work calendars.
What are the other health benefits?
Here’s another image for you. Our cells are constantly working 24/7, receiving, processing and then transporting nutrients in and out of cells. During intermittent fasting these cells actually get a mini break, where they can look around, give themselves a spring clean and reorganise themselves.
The cells tend to become both more efficient and effective and this is possibly the reason for intermittent fasting showing benefits in cell function. Which in turn means better control of cholesterol and blood glucose as well as other metabolic markers.
There’s also an anti-aging element. The body (understandably!) finds not eating slightly stressful and this stress stimulates the cells to break down and regenerate (a process known as autophagy) and these ‘young cells’ work harder and faster than the previous ‘old cells’.
Are there any contraindications (when it’s not good for us)?
So, are there any people who should not do this? An obvious category is children, pregnant women and the elderly who are in poor health. Having certain medical conditions such as type 1 diabetes also means that intermittent fasting should not be attempted, while type 2 diabetics on medication should discuss this approach first with their doctors.
I’d also add that anyone with a history of eating disorders should not follow this diet and, as intermittent fasting does put a slight (albeit positive) stress on the body, highly stressed or highly anxious individuals may find this diet is not suitable for them.
Final thoughts
If you are in good health and fancy giving it a go, here are a few expert tips for gentler forms of intermittent fasting to get you started:
- Tidy up your diet first and base your food intake around 3 meals a day with no snacking in-between.
- Push back breakfast till later in the morning and have a brunch, mid-afternoon snack and supper (it’s a 14/10 approach!)
- Have 2 days a week where you eat ‘light meals’ – for example an apple and 20g of nuts for breakfast, grilled fish and salad for lunch and a large bowl of vegetable soup for supper which comes in roughly at 800 calories. After a few weeks of this you can start skipping the fruit and nuts.
- Do remember the key advantage of this diet is its flexibility. If you start a day of intermittent fasting but then realise it’s not working for you on that particular day, you can simply try again another day.
And, a final reminder that you should always prioritise your health over your weight regardless of the diet you are doing. Eating for your health will automatically help with weight control. Find an approach which works for you and stick with it!
Charlotte Debeugny is a British nutritionist and published author, based in France. www.charlottedebeugny.com
