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Fasting / 5:2 diet

Talk about intermittent fasting and 5:2, including what’s worked for others. Mumsnet hasn't checked the qualifications of anyone posting here. You may wish to speak to a medical professional before starting any diet.

5:2 thread 104: Here's to FAST-ening those jeans!!

265 replies

harriethoyle · 10/03/2026 19:38

Welcome to the continuing thread for those following 5:2 or other forms of IF (Intermittent Fasting) such as 4:3, ADF, etc.

Basically it is 2 very low cal days ("fasts") per week - which need not be consecutive - and eat "normally" to maintain on the other 5 days.
For those who have dieted or maybe overeaten for years, eating "normally"
means roughly the number of calories your body needs to maintain - NOT reduce - its weight (see TDEE calculator below).

IMPORTANT
If you have had past diagnosed Eating Disorders or serious MH problems you should NOT do 5:2 or any other kind of fasting.

JARGON alert
16:8 is a different type of fasting, which can be combined with 5:2.
Daily zero-cal fast for 16 hours and eat within an 8 hour window. To lose weight, this needs a weekly calorie deficit as well
b2b (optional) back-to-back / consecutive fast days, each with an increased allowance of 650 calories instead of 500
BMI (Body Mass Index) healthy range is 18.5 - 24.9 for Caucasians. Upper limit may be 22 for some of Asian origin.
FD = single Fast Day: aim for 500 calories (600 for men or 25% TDEE whichever is higher) or 1000 cals for BF
No alcohol or junk on FDs
Even if you exercise strenuously, do NOT increase FD cals to allow for exercise
MFP = My Fitness Pal, a useful App or website to track food & drink calories
miniFD = MiniFD, tel:850-1000 850-1000 calories, no alcohol or junk
NFD = Non-Fast Day, averages around TDEE
NSV / LSV = Non Scale Victory / LifeStyle (change) Victory, e.g. compliment, smaller waist, clothes size
SV = Scale Victory
TDEE = Total Daily Energy Expenditure, the average number of calories you burn in a day, is calculated from your current weight, height, age, activity level.
Aim to average about this for NFDs.
WOE / WOL = Way Of Eating / Way Of Life. We say this instead of "diet", to emphasise that we must make a permanent change in how we eat, to maintain our new healthy weight long term.

Jump in and say hello!!

OP posts:
harriethoyle · 10/06/2026 10:27

I'm back. I'm as fat as a barrel. Turns out 4 gym sessions don't work out 14 hours of all inclusive a day. Who knew?!

So I am knuckling down. Fasting today and Friday. No booze this weekend.

3 x FD next week, and will keep that up until I am back to my fighting weight. Luckily have got some fairly quiet weeks and, more importantly, weekends coming up. So am going to knuckle down before the next period of indulgence!

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harriethoyle · 10/06/2026 20:09

Kitchen closing on 681. Today has not been easy. Mainly the sobriety!

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harriethoyle · 10/06/2026 21:33

Sooo hungry - had to have some tuna. New closing total: 777.

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harriethoyle · 12/06/2026 09:34

Attempting a Friday fast... will be a loose one as travelling tonight and so tea will be whatever I can forage at the airport which isn't catastrophic but I will stick to FD lunch and hope for the best!

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harriethoyle · 15/06/2026 08:44

Morning all! 1/2 kg lost over the weekend which I’m convinced is due to cutting back on the booze. Only drank on Saturday and stayed dry Friday and Sunday…

signing in for the first of three FD this week. Want to get my holiday weight off asap.

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MadMazie · 15/06/2026 18:33

I did a fast day today after an indulgent weekend. I'm toying with the idea of doing a back to back this week.

Are they ok? Do they feel harder after a day of fasting?
Can I have 800 calories tomorrow if I do this?

harriethoyle · 15/06/2026 18:36

Kitchen closing here on 579.

so for a b2b @MadMazie you get 1300 across the two days. So tomorrow I’ll have 721 to spend. Deduct whatever you ate today from 1300 and that gives you tomorrow’s total.

see you tomorrow if you go for it! I like a b2b at the beginning of the week, it sets me up well.

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MadMazie · 15/06/2026 19:12

I'm a bit scared but I might just try and get it over and done with. I'll see how I feel tomorrow.

@harriethoyle do you find that you're really hungry on the second day?

harriethoyle · 15/06/2026 19:55

Yeah @MadMazie but it’s worth getting two out of the way - gives you way more flexibility for the rest of the week imo

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MadMazie · 16/06/2026 08:59

I'm attempting my first back to back but have decided to bail if I get too hungry.,

harriethoyle · 16/06/2026 09:48

I'm with you @MadMazie - we've got this! Don't go in feeling defeated already - tell yourself you've got this 💪Make sure you've got lots of sugar free drinks, or tea with skimmed milk or black coffee to hand, I find they all help massively.

Check in with me later and tell me how you're getting on!

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MadMazie · 16/06/2026 12:11

I'm pretty hungry now so will be having my meagre lunch soon. I had lost a bit of weight this morning so I'm using that as my motivation not to fall face first into a Gregg's pasty.

MadMazie · 16/06/2026 13:32

I'm now starting to feel a bit dizzy and I can't do my work so I'm going to postpone this fast til Thursday. My period is due tomorrow which isn't helping!

HLBug · 16/06/2026 18:38

I missed my FD yesterday as we were off on the public holiday given due to Scotland qualifying for the World Cup. It was a much needed holiday, despite what Susanna Reid (Good Morning Britain) might have said Grin, as it was an extremely riotous weekend!!! Fasting today though, and closing on 591. Won’t manage a B2B tomorrow as I’m out tomorrow for work drinks. Was going to attempt a Friday FD but it’s the Morroco match that night so I think I’m going to be one and done this week!!

harriethoyle · 16/06/2026 20:19

Closing on 818 - happy enough with that for a b2b and I’m back on Thursday for FD3. Will try and be relatively virtuous tomorrow albeit not fasting 😇

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