So I’d suggest keeping a record of BMI, weight
and
waist
measurement – and then choosing a single goal to focus on. You could express
that as a BMI, a goal in pounds or kg, or a waist measurement ratio.
For example for me, my goal weight is
9 stone 13
,
which is a) in single figures when it comes to stones, just (!) and b)
represents a BMI of 23.83…
Your goal may be less clear if you’re not aiming to lose
weight, but it’s worth doing these, particularly if you’re lean already. You
don’t want to slip into the underweight category as that too can have negative
health implications. If you monitor your weight, you can make adjustments to
how often you fast, e.g. moving from 5:2 to 6:1 with just one fasting day a
week.
Diet calculations: how to
reach your goal
How many days a week can you fast/calorie
restrict?
The diet is called 5:2 by many people because the ratio of 5
‘normal’ days and 2 ‘diet’ days works really well for most people - it offers weight
loss, but it’s manageable in terms of finding quieter days when it works to eat
less, and also means you don’t feel like you’re on a diet most of the time.
But other options for weight loss include 4:3 (with 3 Fast
Days) or Alternate Day Fasting (ADF). Here’s a selection of how the choices our
dieters have made suit them.
Every other day - 500 calories.
Sally, 49
I follow standard 5:2, but probably consume 7-800 calories
on fast days (but I'm tall and exercise a lot).
James, 43
Two days and I aim for about 600 calories
a day as I don't need to lose weight.
Nina, 52
Two days. 300 calories.
Sarah, 37
Of course, the more often you fast, the faster you’ll lose.
For those mainly seeking the health benefits, without weight loss, 6:1 seems to
be the preferred option.
How much should you eat on this diet?
Fast Days (the 2 in the 5:2 diet) are when you are
restricting your calorie intake to approximately 25% of your daily calorific
requirement (DCR).
I’ve outlined how to calculate your DCR below, because I
wanted to do that myself, but since the first edition of the book, I’ve
realised most people prefer to stick to the averages, which is much easier and
works very effectively for most people.
The average active woman needs approximately 2000 calories
per day - or what we know of as calories: most food labels list kcals or kilo
calories but the term ‘calories’ is used interchangeably in most diet books,
including this one. So your goal intake for Fast Days is 500.
Active men need on average 2400 calories a day so they get
an extra 100 cals or a goal intake of 600 calories.
Still want to find your own precise goal? It’s easy as ABC
and may give you a higher goal, particularly if your BMI is very high and you
have a lot of weight to lose.
Stage A: what a girl (or guy)
needs
Begin by working out your Basal Metabolic Rate - how many
calories someone of your size, height and age needs for survival without weight
loss. That is, to keep your most basic functions going. There are two different
formulas: the Harris Benedict and the Mifflin St Jeor: the latter takes age
into account so that’s the one I’ve included.
Mifflin St Jeor:
Male: BMR = 10×weight in kg +
6.25×height in cm - 5×age + 5
Female: BMR = 10×weight in kg
+ 6.25×height in cm - 5×age - 161
It’s
much
easier to use an online calculator,
especially if you work in pounds and feet because it’ll do the conversion for
you without any extra steps. For example, a fifty-year-old man, 5 feet 10 tall,
and weighing 14 stone (196 pounds) has an estimated BMR of
1755 calories per
day
Stage B: factor in your
activity level
The BMR sounds low – so now we factor in how active you are,
to give a truer estimate of your actual Daily Calorie Requirements.
Little/no exercise:
BMR x 1.2 = Total Calorie
Need
Light exercise:
BMR x 1.375 = Total Calorie
Need
Moderate exercise (3-5
days/wk):
BMR
x 1.55 = Total Calorie Need
Very active (6-7 days/wk):
BMR x 1.725 = Total Calorie
Need
Extra active (very active
& physical job):
BMR x 1.9 = Total Calorie Need
You can use online calculators
for this too, but it’s a simple calculation. Our male dieter takes limited
light exercise, so we multiply his BMR by 1.375:
= DCR of 2413 calories
Stage C: Lower, lower!
So to maintain his weight, our male dieter could eat up to
2413 calories. But he’s fasting to lose weight and for the health benefits, so
on Fast Days he needs to eat a quarter of his DCR.
2413 ÷ 4 = 603 calories
Is it worth it?
So… After all those sums, we’ve ended up very close to the 600
average goal for men. It’s up to you whether you want to do this yourself – as
I say, if you’re heavier, you may find this gives you a few extra calories to
play with. In my case, as I record in my diary, I ‘lost’ 30 calories as my goal
was 469 – but I suspect my weight loss would have been pretty much the same had
I aimed at 500.
If you make these calculations and then lose a lot of
weight, you’d want to recalculate, as your calorie requirement decreases as
your weight does – UNLESS you step up your levels of activity, which may well
happen as you find you have more energy and confidence.
The sums are finished. Time to tailor the
diet to suit you!
Which day(s) do I fast?
Picking the right days will improve your chances of success.
The first time(s) you fast, you’re likely to feel hungry at
first, with possible other side-effects like headaches, or feeling cold or
slightly light-headed. Most of us become used to this very quickly, but it
makes sense to schedule your first couple of Fast Days for days when you have
fewer commitments and can afford to take it a little easier.
Though it’s best not to clear your diary completely – most
of us have found that staying busy is the best distraction from any hunger
pangs.
Choose days when you have no food-based social events, or
don’t have to be around people who might be sceptical or try to persuade you to
give up. If you are responsible for family meals, then try to build in days
when the meal is healthier and you can have a small portion without attracting
too much fuss. I like to do my Fast Days when my partner is working late or
socialising with friends because that way I won’t be tempted to eat what he’s
eating at home!
It can be useful to have regular days e.g. Monday and
Wednesday, because you can schedule around them. At first, I didn’t exercise on
Fast Days so scheduled around that. But it’s your diet - feel free to
experiment.
I definitely find it helps to mark the Fast Days on my
e-calendar and to-do lists – this way I feel that I have committed to them!
If a ‘whole day’ fast doesn’t work for you, some people fast
for part-days, but still for twenty-four hours. So you might eat a normal lunch
on Monday, then stick to 500 or 600 calories until a later lunch or early
supper on Tuesday evening.
When do I eat on my Fast Days?
You can choose to eat your calorie allowance in one, two or
even three meals, although evidence suggests that the health benefits may be
higher if you restrict to two or one meals, with as little snacking as
possible.
This is how Krista Varady’s study worked: with participants
having a single, larger meal at lunchtime on their ‘fast’ days. It makes sense
to me because it appears to give the body less to ‘do’ in terms of digesting
food, producing insulin etc. Dr Mosley, by contrast, decided that he would eat
two meals and it still worked for him, both in terms of weight loss and
reduction in IGF-1.
At the start, I could never have imagined a whole day
without any food. But five months in, I frequently eat only in the early
evening on a Fast Day, to try to maximise the health benefits, and I don’t find
it difficult at all.
Equally, if it’s cold and I want some soup at lunchtime to
warm myself up, I don’t worry too much. And neither should you if you want to
have three meals. You’re still doing something great for your body.
That’s the beauty of this diet compared to all the others
I’ve tried (and abandoned): you decide how to make the diet fit your life,
rather than the diet dictating how to live it. Here are how some other dieters
divide up their Fast Day calorie allowances.
No
breakfast. Porridge midday. Veg soup in evening. Couple of barley cups during
day and perhaps a rice cake.
Stephen, 47
One
meal in the evening with my family. Portions small except for green salad/veg. An
entire bag of salad is circa 40 calories (a single egg is circa 80 calories and
as for cheese or, god forbid mayonnaise…!)
Myfanwy, 49
I
can't do just one meal a day as I need the psychological feeling of having
three meals a day.
Nina, 52
Minding the Gap
There’s another way to try to maximise the health benefits –
and that’s by being aware of the gap between the last meal on Feast Day and the
first on Fast Day. And then doing the same when it’s Feast Day again. I do
this, as it seems to make sense to increase fasting time. For example:
Monday Feast Day:
Eat dinner at 6pm
Tuesday Fast Day:
Eat main meal at 6pm (no
breakfast or lunch)
Wednesday Feast Day:
Skip breakfast, eat lunch late
e.g. 2pm
Some 5:2 dieters do go for a ‘full’ fast, where you only
drink water or herbal teas. If the ‘gap’ planning above is taken into account, you
could fast completely for 44 hours, but there would only be one day where you don’t
eat.
Monday Feast Day:
Eat dinner at 6pm
Tuesday Fast Day:
Fast completely
Wednesday Feast Day:
Skip breakfast, eat lunch late
e.g. 2pm
Bear in mind that total fasts can be harder to stick to,
but there are many alternatives, such as compressing your mealtimes into a
small ‘window of eating’, so you avoid food for twenty hours and limit eating
to between, say, 1pm and 5pm. Again, this may maximise the benefits.
I
try to postpone eating all day so I can eat in the evenings but I'm not sure
this helps much. It probably does re: the metabolic changes needed for fat
mobilisation and brain growth, because the longer we go, the better it is, but
it might undermine the repair at night side of things. The research suggested
eating at mid-day but I fear once I start eating I would want more.
Linda, 52
The truth is that there isn’t a study I’ve found comparing
different fasting configurations. I am sure that will come, but in the
meantime, experiment to find
your
best approach.
Consecutive or non-consecutive?
Most people schedule the days non-consecutively as the
hunger pangs can be stronger and a two-day fast can become an ordeal rather
than a ‘mini-break’. This risks making it less sustainable than the
non-consecutive option. Some doctors would also be wary of someone undertaking
a fast for more than twenty-four hours without being checked thoroughly
beforehand, and maybe being supervised.
WHAT will I eat on my Fast Day?
Exactly what you like… so long as it doesn’t exceed your
calorie limit.
500 or 600 calories isn’t a lot to play with. But, take it
from me, you
can
still make satisfying choices.
Banana
for breakfast. Apple and yoghurt for lunch. Chicken and salad for dinner.
Karl, 49
Loads of cups of tea with a little milk,
nothing till supper, then a normal family supper with few/no carbs.
Julia, 50
Only water!
Rob, 42
All home-made food so it's hard to work
out the calories. I'll avoid carbs and alcohol and have a small helping of
chicken or fish and lots of vegetables - a bowl of home-made soup and fruit for
the other meal. I'm aiming to only eat between 12 and 6, too, on most other
days.
Linda, 52
I stick to fruit and veg, beans on toast,
soups, Weightwatchers ready meals.
Jane, 49
There are plenty more sample menus and food ideas in the
third section of the book. I do recommend planning in advance - the very last
thing you want to be doing on your first Fast Day is going into the
supermarket…
Obviously, it also depends on how many meals you’re planning
to have - it’s very easy to find ready-meals with 400-500 calories if you’re
only having a single meal, but it gets slightly harder if you want two or even
three. That’s where soups come into play - they tend to fill you up for longer,
with fewer calories.
I am also more careful to remember to take a multi-vitamin
during the fasts: not because I think a day or two of eating less will do
serious damage, but it’s a good insurance policy.
HOW will I monitor what I eat on Fast
Days?
Studies suggest that dieters who keep a record of what they
eat tend to be more successful, and it will help you pinpoint where you might
be going wrong if you need to amend your habits or consumption. You can either
do that electronically, or jot it down in a notebook.
The brilliant thing about 5:2 is that most of us only need
to record what we eat on Fast Days – so much less hassle. If you’re eating ready-made
meals, recording your consumption can be very easy. They all have the
nutritional information on the packet or just scan the barcode if you have MyFitnessPal
on your phone. Online sites allow you to keep your diary completely private or,
if you find it helps to keep you motivated, share it with others.