The Fast Diet – Does 5:2 Intermittent Fasting Work?
The word “fast” in fast diet doesn’t mean speed. This isn’t a rapid weight loss plan.
It’s about fasting 2 days out of every 7.
And it’s not a fast in the sense of eating nothing.
It’s actually a reduction in your calorie intake to around a quarter of the regular amount.
So on fast days, women will be eating around 500 calories and men around 600 calories.
Does the fast diet work?
Yes!
There have been lots of case studies as well as reports from people who’ve bought the book and followed the ideas that it does work.
My initial thought when I started using the fast diet (something I still use regularly for reasons we’ll go into a bit later) was that I’d compensate for the two low calories days on the five unrestricted days.
But that doesn’t seem to be the case – and I’m not alone in that. Most people find they maybe eat slightly more than before on the non-fast days or maybe eat what they would have eaten. Maybe because our stomach contracts over time, so we feel full earlier.
It does require a bit of planning but not too much.
Is the fast diet safe?
Again, the answer is yes.
It’s maybe even better than safe.
We’re not genetically engineered to binge on food day in, day out.
When we were hunter gatherers there would have been days when our prey didn’t want to be preyed on. So we’d have gone hungry.
There would have been days when the birds and beasts got to the fruit, nuts and berries before we did. So we’d have gone hungry.
It’s in our makeup to fast.
But the science is even nicer than that…
The fast diet helps to repair us
When we’re eating less calories than normal, our bodies go through several different stages – they eat up the “easy” food reserves first and then move on to the harder reserves.
But at the same time, our immune system sets about getting rid of the damaged cells that we’re carrying around with us.
In normal times, we’d just let these passengers hitch a ride.
But when calories are scarce, that’s a luxury we can’t afford.
So our body has a clear out.
OK, there’s a lot of technical details going on behind the scenes (the book goes into these in some depth) but that’s the executive overview.
With fasting, lots of healthy white blood cells get produced.
If you can fast for 3 days you’ll kick start the diet even more and regenerate your entire immune system.
But regular 2 days on, 5 days off has a similar effect.
A weird fast diet tip
Reading the book, I was surprised by one of the studies.
Scientists like having control groups – ones that just carry on as before.
This time, they gave both the control group and the test group a diet to follow.
One group did what most Westerners do – they basically grazed.
Their calorie allowance was eaten over 6 different times of day – the main three meals and some snacks.
The weight loss group ate the same amount of calories but were more regimented. They split it between two meals a day.
So…
Same calories.
Just a different eating plan.
Surely the weight loss would be the same? After all, they’re eating the same amount of food.
This is where it gets weird…
The two meals a day group lost more weight.
Which could be why those “skip breakfast” diets work.
Part of the logic for this is that the body is kind-of fasting every day if you only have two meals a day.
Let’s say you have lunch at noon and your evening meal around 6pm.
Which probably isn’t much different from the times you currently eat those meals.
What that means is that between your evening meal and your next meal (lunch), there’s around 18 hours of fasting.
So the body starts to think “oh no, not again” and question your ability to catch your next meal.
The fast diet in a nutshell
For two days a week – any two days, your choice – eat a quarter of your normal calorie intake.
That means 500 calories for women, 600 calories for men.
Either eat your allowance all at one meal (that’s what I do and once you get used to it, it’s easy) or split it over 2 meals.
If you’re going to split it, lunch and evening meal is best but breakfast and evening meal or breakfast and lunch work as well.
The other 5 days a week, eat normally. No restrictions.
Obviously if you can incorporate healthier food into that regime then that’s even better.
A quick way to do that is cut out as much processing as possible.
And read the ingredients list on the foods you buy.
Or, if you’re feeling lazy, look at the length of the ingredients list – any more than a handful of ingredients means be careful.
Fast diet side effects
Any diet has side effects.
The one I’ve found most regularly with almost any diet – and the fast diet is no exception – is headaches.
For me, headaches normally crop up if I’ve had too much caffeine (coffee is my favourite delivery package for caffeine) and chocolate in the preceding days.
If that happens to you, wean yourself off caffeine and chocolate rather than going cold turkey on them.
Or just tolerate them, maybe with the help of a painkiller.
They will pass.
And they’re your body’s way of telling you that something nasty is being dealt with.
I’ve cut down my caffeine intake – most days no more than one or two cups of coffee – and found that for me that’s a good balance between not getting headaches if I cut out caffeine completely for a few days and enjoying drinking coffee at other times.
Another rather nice visible “side effect” is obviously the weight loss.
500/600 calories is a bit of a struggle at first.
But you get used to it.
Personally, I find the recipes in the main book a bit fiddly.
Some of them are a bit “cheffy” but once you’ve cooked them once you’ll know which steps you can combine or miss out completely.
They’re calorie counted, tasty and filling.
And they work very nicely with having just one meal a day although there are some that you could use “as is” on two meals a day. Or you could just divide the portions.
But that doesn’t seem to be the case – and I’m not alone in that. Most people find they maybe eat slightly more than before on the non-fast days or maybe eat what they would have eaten. Maybe because our stomach contracts over time, so we feel full earlier.
