The FastDay Forum

Lots of talk here about eating to TDEE on feed days. Now I have watched Eat Fast Live Longer and I have read the Fast Diet book and I have looked at the 'official' website for 5:2 and nowhere do I see a reference to TDEE and counting calories on feed days. Is this something that has come about from this forum/experience or is this a recommendation from some scientific trial or from Dr Mosley? I don't count calories on feed days as I was attracted to this 'diet' by the fact I didn't have to diet 7 days a week & this is what I have read in the Varady research & the Fast Diet book. Can someone enlighten me

[Moogie]

The original 5:2 method is based around eating a normal amount of calories on your feed days, with the average 'normal' being accepted as around 2000 calories. For some folks however 2000 calories is more than what their body needs to maintain weight, often due to activity level or other factors.
TDEE is basically a reading for your own 'normal' calorie requirements.
It's not so much about calorie counting on feed days but learning what your energy needs are and how to judge that automatically without strictly counting.
It also serves as a reminder that as you lose weight your energy needs decrease and continuing to eat to your old energy needs may result in a plateau or reduction in loss.

It's true, you don't HAVE to count calories on your non-fast days, but you do need to eat 'normally'. The problem is that a lot of us don't know what 'eating normally' is, otherwise we wouldn't be here in the first place.

One way to found out what eating normally means is to find out how many calories your body needs every day to do the things you ask of it. This is your TDEE. If you consume too many more kcals more than your TDEE on your non-fast days you won't lose weight and you might even gain weight.

If you are losing weight by not counting on your non-fast days, then that's great, and keep doing what you are doing. Your BMI is in the normal range anyway, so maybe you have a better idea of what 'eating normally' is than some of the rest of us.

Some people have found that counting calories on their non-fast days for a couple of weeks has given them an indication of what 'eating normally' looks like and after a few weeks this has enabled them to re-educate themselves into better eating habits.

At the end of the day, this is a totally flexible WoE and you have to find what works for you. If knowing your TDEE and eating to it works for you, that's great. If it doesn't, don't do it!

I would endorse what Moogie and Jemima have said.

I didn't really understand all the talk on here about tdee either. I didn't/ don't monitor what I eat on non fast days or consciously try to restrict. I found after about a month I just started to eat less on non fast days without thinking about it.

However, I know some people struggle not to overcompensate on non fast days and end up bingeing so using the tdee to keep an eye on what they eat is very helpful.

The trouble is most of us over ate before doing 5:2 so Dr Mosley's advice to eat 'normally' isn't necessarily helpful if you haven't eaten normally for years. So tdee tracking gives a bit of help in that direction.

No need to calorie count, assuming that you eat sensibly/as much as you need to maintain.

Moogie aren't u sposed to be on holiday
Yes I understand all that - so it is something that this forum has found works rather than coming from Dr M? However my query is not so much WHY TDEE but whether any of these scientists or Dr M have suggested it.

I think that Dr M was a bit vague regarding the eating habits of a non-fasting days...

I know that if I ate 2000 cals each non fast day, I would be HUGH! First post, but I do watch my tdee. I have lost over 20lbs.

For just a few weeks I have been logging calories (my fitness pal) on normal days just to see what my mind thought was normal. I found that my calorie count was going way above my recommended TDEE. This has "re-educated" me over time and I am truly more aware. (Age, lost weight and moderate activity factored in).

E.g. Yesterday after a 3 course meal provided at a workshop weekend, plus my normal breakfast and lunch at home and with NO fanatical counting, I have just logged the approx calories for the day and I am just above my TDEE. With two fasting days at 403 cals my weekly average was kept below TDEE and I have lost weight again. Feel pleased to be "winning" and to be happily relaxed about it all. That is surely the idea behind 5:2.

I would agree with tweaking what one thought was normal.

GMH - this forum didn't invent TDEE (if you google it you'll find it on hundreds of dieting/ bodybuilding sites) but it certainly has raised everybody's awareness of it. I had not heard of it before I joined this forum and I'm sure lots of others hadn't either. TDEE is a ball park figure but it's far more accurate than believing that every woman can maintain a perfect figure on 2000 cals a day - that is complete rubbish.

Chutneymaker - welcome to the forum! That's a fantastic weight loss! How long have you been doing 5:2?

Yes I understand all that - so it is something that this forum has found works rather than coming from Dr M? However my query is not so much WHY TDEE but whether any of these scientists or Dr M have suggested it.

All of the clinical trials use estimated energy requirements (ie TDEE) for example ADF protocols using 25% / 125% of TDEE.

Dr M I believe says something along the lines "a quarter of recommended calorie intake" and uses "standard" figures of 2000 (f) and 2400 (m) to come up with 500 and 600.

A typical Varady study says....

Before commencing the 8-week ADF intervention, each subject participated in a 2-week baseline weight maintenance period where they consumed either the HF or LF diet (providing 100% of their energy needs). Energy requirements were calculated using the Mifflin–St. Jeor equation.

All subjects consumed 25% of their energy needs on the fast day (24 h period), and 125% of their energy needs on the feed day (24 h period). Subjects were provided with 3 calorie-restricted meals on each feed day and one calorie restricted meal on each fast day.

I had heard of TDEE but I didn't know it was called like that. We called it "maintenance calories".

PhilT, can I hijack here to ask you about you - I really value your scientific contributions to the forum but I haven't seen you comment on your own experience. I don't mean this in a challenging way, I'm genuinely interested. Are you doing 5:2, what variation and have you lost weight? Or are you just interested in the science of it all. I'm assuming from your learned contributions you're a medic - or maybe just all round smart guy?! Anyway, thanks for the objective advice on all things 5:2!

In the words of Mr Micawber in David Copperfield,

"Annual income twenty pounds, annual expenditure nineteen [pounds] nineteen [shillings] and six [pence], result happiness. Annual income twenty pounds, annual expenditure twenty pounds ought and six, result misery."

See calories in the same way. Daily TDEE 1500 calories, expenditure 1499; result, happiness. Daily TDEE 1500 calories,expenditure 1501, result fat.