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5 2 diet – An insider’s guide to intermittent fasting!

5 2 diet – An insider’s guide to intermittent fasting!

Diets, Featured, intermittent fasting, Nutrition, Weight Loss and Dieting

The 5 2 diet is a type of intermittent fasting which become extremely popular in the UK in 2013 following the release of ‘The Fast Diet’ by Michael Mosely and Mimi Spencer, based on promising nutrition research. Michelle Harvie, a research dietitian published two studies in 2010 and 2013  which concluded that intermittent fasting was as effective as calorie controlled diets for weight loss for women as well as being possible more effective in terms of fat loss and blood sugar control ( a win, win, win!)

What is the 5 2 diet?

It is a combination of intermittent fasting and calorie restriction.  You eat ‘normally’ 5 days a week while restricting your calorie intake to 500-800 calories on the other 2 days, which are known as ‘fast’ days.

Though these 2 days are called ‘fast’ days, you do not have to fast completely, you can eat light meals provided you consume less than 500-700 calories.

Why is there a limit of 500-700 calories on the 2 fasting days?

It is a question of maths!   Reducing your energy intake to 500 calories on 2 days of the week is equivalent in energy reduction to consuming 25% less energy every day. The weight loss effect of eating less just 2 days a week, is similar to the weight loss effect of eating less on a daily basis.

A recent change has been increasing the number of calories you can consume on a fast day from he 500 calories to 800 calories. This makes the fast days a little easier (!) and consuming up to 800 calories is still effective for weight loss.

The advantage of the 5 2 diet is that you only need to eat less on 2 days a week, which can make the diet easier to follow in the longer term than struggling to eat less every day.

How much weight can you lose?

A similar weight to any other diet, which is on average 2-3 kg a month, though this can vary according to individuals.  We are all wonderfully unique and weight is strongly associated with genetics, hormones, diet history, medications…….The objective is a healthy weight loss which works for you.

Is the 5 2 diet more effective than other diets for weight loss ?

This really depends on your definition of effective!  The weight loss is similar to other diets, but one of the benefits  of the 5 2 diet is that some people find it easier to follow. They just need to diet  2 days a week while eating their normal diet on the other 5 days.

It might also have a slight edge to other diets in terms of fat loss and other health markers, but more studies are needed to confirm this.

Some people have found that this method of dieting helps them to better control their appetite on the non-fasting or normal days.  The fast days help them to adapt their portion sizes, naturally eating smaller portions during the week.  So, the 5 2 diet might help support long term behaviour change with less snacking and better portion control.

Do the 2 fast days need to be consecutive?

You can choose the 2 fast days to suit you and they do not need to be consecutive.  You can vary the days according to your work and social agenda. The key word is flexibility!  I tend to do my first fast day of the week on a Monday and then do a second fast day either on Wednesday or Thursday and this works very well for me.

What should I eat on the fast days?

There are no fixed rules!  Given though that you only have an ‘allowance’ of 500-800 calories to spend, it makes sense to spend it wisely!  Focus on foods which are digested slowly and help you to feel full such protein rich foods (such as meat, fish, chicken, eggs, lentils and beans) in moderate quantities.

You can then add bulk in the form of green and leafy vegetables – you can for example eat a field of spinach for 10 calories 😊 (a slight exaggeration, but you get the idea!).  So, the aim is to fill yourself up with high-volume low-density foods to manage hunger pangs.

Fats will need to be moderated on fast days.  A teaspoon of oil is a whopping 50 calories, so add fats cautiously, through you can certainly give yourself a small allowance for cooking and dressing your meals.

How many meals should I eat on the fast days?

Again, this is your choice.  Some people prefer to graze, eating little and often.  Others prefer to have just 1 or 2 meals.   I prefer to skip breakfast and split my calorie allowance over 2 meals, but this is my personal preference  The most important objective is to ensure your calorie intake stays below 700 calories.

What about the other 5 days?

This is a good question! On the other 5 days you eat ‘normally’.  This means in terms of energy intake, roughly 2000 calories for women, so no more and no less.   The fast diet will not work if you overeat on the other 5 days!  I’d recommend tweaking the quality of the foods you eat on the normal days, if necessary, to ensure you consume all the nutrients you need, particularly as it is difficult on the fast days to consume all the nutrients you need with the calorie limit of 800 calories.

The aim for the non-fast days  is a Mediterranean style diet with lashings of vegetables, good quality protein, unsaturated fat and whole grains.

You can certainly enjoy a moderate intake of alcohol and added sugar, but this should be moderate, roughly 1-2 a week, no more!

Can I exercise on the fast days?

Yes you can, but I’d recommend beginning with gentle exercise as opposed to planning to run a marathon on a fast day! So possibly start with yoga and walking and see how you feel.  I would also suggest having some fruit/dried fruit to hand just in case you need some additional energy after an intensive exercise session.

Is there anyone who should not try the 5 2 diet?

The 5 2 diet is generally suitable for healthy adults.  It should not be followed by children, during pregnancy or if you have any condition that requires regular meals (such as diabetes type 1).

It is also not appropriate for anyone with a history of eating disorders.  So, do check with your doctor if you have any doubts.

How can I sustain my weight loss on the 5 2 diet?

This is the million-dollar question!  Weight loss is not just about losing weight.  It is about then being able to keep the weight off.  Some people continue to follow the 5 2 diet but just fast one day a week (a 6 1 diet! 😉) while others manage by ‘eating normally’ but with the awareness of portion sizes which they learnt while following the 5 2 diet.

Charlotte’s comments

I do like the 5 2 diet, although I struggle to eat less than 800 calories.  I love the flexibility of this diet and the fact that you do not have to ‘diet’ every day.  I tend to split the 800 calories over 2 meals and skip breakfast.  I have also found that it is easier to control my appetite if I include a protein rich food at both these meals.  Soups are also a good choice, as they are a great example of a high volume but low energy meal.

I like to save some of my calories for a light snack before bed, as I find if I go to bed too hungry, it is impossible for me to sleep.

So, a typical day for me is:

Breakfast:  Tea or coffee  ( I have a dash of milk)

Lunch:  100 g of chicken or fish and a very generous serving of green vegetables (broccoli, spinach) as well as a handful of other vegetables of my choice.  1 tsp oil for either cooking or seasoning

300 kcals

Snack:  A fruit of my choice

60 kcals

Supper:  A large bowl of ratatouille with a poached egg

300 kcals

Before bed:  An oat cake with 1 tsp low fat cheese cream or a natural yogurt with a drizzle of honey and an herbal tea

@ 80 calories

Total calories = 740 for the day 



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