Fasting, weight loss and understanding why 5:2 alone may not always work for everyone!!

Let me introduce a fictional friend to you, I’ll call her “Samantha”.

Samantha is aged 45, has a sedentary lifestyle (little or no exercise, desk job). She’s 5ft 6 inches tall and weighs 12 stone. TDEE = 1,709 calories. BMR is 1,424 calories. BMI is 27.1

For more explanation on TDEE, BMI, BMR see the link to the TDEE calculator.

Many people seem to get disheartened about small losses, staying the same or… re-gaining weight lost following a Fasting day a day later!

In order to lose 1lb in weight, you need to create an approximate deficit in your calorie intake (so over the TOTAL calorie intake or total TDEE calorie total for the week) of 3,000 calories. Clearly, there are other things that will affect this figure – how active you are, age, etc. Fasting (2 days per week @ 500/600 calories) will create a deficit.

Using Samantha’s TDEE, she’d need to eat 11,963 calories a week to maintain her weight. Because she’s reducing the calorie intake on 2 days a week (2 x 500 = 1,000) she has created a 1,209 deficit on one fasting days – or 2,418 calories over 2 days. If she eats up to her TDEE on the remaining 5 days (5 x 1,709 calories) she’s consuming just 9,545 calories in a week – 2,418 calories BELOW her TDEE for the week (11,963 – 9,545 = 2,418).


BUT if Samantha completes two successful 500 day fasts and on the remaining days eats OVER her TDEE, then she’ll soon start eating into the 2,418 calories she’s “saved” through her fasts. She may just have a couple of things that take her over her TDEE on each non-fasting day – half a bottle of white wine at 635 cals and a Magnum (280 cals) = 915 calories! She may not do this every day…. But if she did, then potentially she may have completely negated the fasting days. Over 5 days, her wine and Magnum have totalled 4,575 calories!!! She’s actually eaten 2,157 calories OVER her TDEE.She probably believes that she’s doing ok, as she has absolutely no idea of how many calories are in a Magnum (she doesn’t count calories on non-fast days) and alcohol – well, there aren’t many calories in it are there? It was only half a bottle (she used to drink a whole bottle before 5:2) and…. it’s a non-fast day so she’s not counting calories…..

I am posting this, a

2.5 years and 4.5 stone….

s someone who started off with logging food and calorie counting – 5:2 hadn’t been heard of in 2012…. At 50 years old, I weighed 14 stone. Was a size 24 and am just 4ft 9 and very sedentary because of a physical disability which severely impacts on my mobility. I use an electric wheelchair outside of the house.

It took me 3.5 years to reach my goal weight of 9st 7lb. During the second part of my weight loss journey, I used (and still use) 5:2 as a “tool”.

I have during the whole of that time continued to log all the food I eat.

I’m posting this, because it may be that some people do need to “number crunch” and look a bit more closely at what they eat on non-fasting day – particularly the calorie count. Examining some of the calories in food (especially high calorie foods and alcohol) enables you to start making better food choices… “Is that 400 calorie slice of cake really worth it?”

You will also need to develop huge willpower to resist temptation! That lovely crisp warm sausage roll may smell nice and taste delicious! However, is eating it knowing that it may mean that you don’t see a loss at the end of the week really worth it? The feeling that you have “failed” stays with you much longer than a few moments and the more you experience that feeling of “failure”, the more likely you are to give up altogether.

The TDEE comes down as you lose weight, so it’s important that you regularly check your TDEE calories. Yes, the beauty of this way of life is that it’s easy, it’s sustainable and for many, it works successfully. BUT sometimes it may be helpful to study exactly what a non-fasting day looks like and work out if this might be contributing to the lack of movement on the scales…..

I am hoping that if you’ve made it this far in my post – it’s been helpful! 🙂

More than anything, stay strong…. it’s not a race. You can get there in the end, and it will be sooooo worth it!

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