It was only a few years ago that 5:2 diets swept the nation and revolutionised the way we thought about dieting thanks to Dr Michael Moseley’s BBC TV programme, Eat, Fast and Live Longer, and his subsequent book, the Fast Diet. But another form of fasting is grabbing headlines: 16/8 diet.
It doesn’t seem like a year goes by when a new diet is invented. We know that all diets work so long as we stick to them and follow them by the letter. The main problem with diets is they don’t tend to work long term. That is, many people put the weight back on, and often more!
The best diets are the ones that permanently change our way of thinking about food, ones that we can stick to and make part of our lifestyle.
The thing is, if we’re overweight, then we’re prone to being overweight. And so we have to adopt measures that stop us from getting that way in the first place; or to keep ourselves from expanding any further.
And I’m one! At my worst, I am 95kg. So I am officially overweight, but not obese. That’s because my body mass index (BMI) fluctuates between 25 and 27. It could easily go much higher if I don’t discipline myself not to go back for seconds!
What is the 16:8 Diet?
One of the benefits of the diet is that it appears to be easier to follow
The 16:8 diet is another intermittent fasting diet, but this one doesn’t restrict calories. The problem with the 5:2 diet is that, whilst the fasting days are only limited to two per week, and you could choose whichever two days you like, it is very challenging on the fasting days because you cannot consume more than 500 or 600 Kcals.
And for a lot of people, that just makes them hungry, moody, tired and irritable. Your body can adapt over time, making the process easier – but too many people struggle with this in the long term and give up after only a matter of weeks.
The principle behind the 16:8 diet is that you simply have a “feeding window” and a “fasting window” – everyday.
As you know, there are 24 hours in a day; now if you restricted your eating to just within an 8-hour window, and take nothing but water in the other 16 – you’ll both lose weight and maintain it.
At least, those are the claims.
Where did it come from?
It’s uncertain who first came up with this principle, but certainly Martin Berhan and his Leangains programme had championed 16:8 intermittent fasting way back in 2010.
David Zinczenko published his book, The 8-Hour Diet in 2013, which is based on the principle of 16:8 diet.
However, intermittent fasting has been around for thousands of years – often practised for religious reasons, particularly in Hinduism, Buddhism and Jainism – but probably most widely known in Islam during Ramadan.
But fasting specifically for weight loss is probably more recent – and certainly still popular judging by Google search statistics.
All fasting diets are based on the idea that, whilst we’re not eating, our bodies are forced to dip into our fat reserves – and putting us into what is coined as a ketogenic state. It basically means that we use ketones rather than glucose for energy.
It’s the same principle behind very low carb diets.
Does it Work?
To make a statement about any type of diet working, you need long-term studies. They just don’t really exist for this type of diet.
However, very recently a study was published that hit news headlines:
The 16:8 Diet Might Actually Help you Lose Weight: Women’s Health
Daily Fasting Works for Weight Loss: UIC Daily
The study was based on 23 obese participants that had an average age of over 45 years. Over a period of 12 weeks, they were given instructions to consume food only between the hours of 10am and 6pm – but that was the only restriction.
Between those hours, they could eat whatever they liked and in whatever quantities. Outside those hours, only water or calorie-free drinks were allowed.
The results were compared to another historical group who used the alternate day fasting method of dieting.
They found that, despite being allowed to eat anything, most people ate 350kcal less, lost 3% of their body weight and had lower blood pressure as a result!
High blood pressure is a risk factor for heart disease, strokes, kidney and eye damage. So to have improved blood pressure without dramatic weight loss was a surprising find.
One of the benefits of the diet is that it appears to be easier to follow, as the only thing to remember is the time you can start eating and the time from which you must stop. The rest is fasting – and because half of the fasting time is spent asleep, it doesn’t seem so difficult to maintain.
The fact that much fewer participants dropped out of this study is a good indicator that complying to the rules is easier for a lot more people.
For me, any diet that improves cardiovascular risk factors such as blood pressure is going to grab my attention.
This does not, by any means, suggest that one single small study is a game-changer in dieting history – it simply means that it may work for some people – but much much larger studies are required.
Nor do I think it’s sensible to eat whatever you like and in whatever quantities. If you follow this diet, the same healthy eating principles must remain.
I do try to discipline myself not to eat after a certain time. I like to give my body a rest from digestion for as long as I can, by eating my last meal early and my first meal late. I haven’t actually achieved 18 hours though, I average about 15. But then, I’ve never tried!
The reason I do this is mainly to encourage the best balance of gut bacteria, which I know will protect me against a number of diseases as I age. Fasting improves the type of bacteria ratio we have (in terms of firmicutes vs. bacterioidetes).
But then, so does what we eat – particularly a good range of dietary fibre from vegetables and grains.
Keeping my blood pressure low is also important to me as I get older. So extending my fasting hours is certainly something I will consider quite seriously – and I’m not one for diets at all! I prefer just to eat healthily.
I think it’s important that we continue to eat a good range of fruit and vegetables, reduce meat, increase fish and pulses and definitely introduce some sort of fun type of exercise (such as walking, cycling, or running about the park with the dog).
But restricting food in a time frame? Why not, it makes some sense to me.
If you look back in our history, the human body is well-adapted to fasting. It’s really only since mass food production began have we indulged in so much food – largely because it’s so much more freely available than it ever was.
And this has encouraged us to eat around the clock – particularly snacking!
What we must be careful with, is any message that makes binge-eating in any time-frame seem acceptable. I would whole-heartedly discourage following a 16:8 diet if it meant bad eating habits in the eating window.
And we should also follow diet books with care – the authors of these are driving a message, and are highly prone to what we call in science confirmation bias. That means they pick and choose their science to back their message.
Yes, I’m afraid even those with PhDs and medical degrees! So I personally wouldn’t just buy a book just because the author appears highly educated.
Pixabay – DeepKhicher
Seb is a writer and blogger of food and nutrition. He holds a bachelors and a masters degree in nutrition science, and has studied sports and exercise nutrition at postgraduate level. He specialises in plant-based nutrition and believes passionately that we can all live with a little less meat.