The FastDay Forum

Hi! I just finished my second fast day yesterday and it hasn't been too bad!

In the way of providing some background before I get to the actual question, I am 59 years old, female, started a calorie restriction diet about 7-1/2 weeks ago and have lost about 12 lbs so far. My starting weight was 182, and I am 5'6". I have been pretty consistently limiting my calories to about 1000/day (calories eaten - exercise calories burned = net calories). It has been working for me and I believe I can continue with it long-term to reach my weight goal of 130. I decided to incorporate intermittent fasting NOT for weight loss, but for the potential health benefits. So now to the question:

If I continue eating the 1000/day net calories on feast days, will my body recognize the 500 calories on fast days as enough of a reduction to actually consider it a "fast" day (since 500 is still 25% of my TDEE )? Or would I need to reduce the intake even further to just 250/day (for 25% of what it now thinks of as "normal" caloric intake)?

I hope that made sense and thank you!

Hello Ahroo and welcome to the forum!

I'm a bit unclear about your real calorie intake and your TDEE. I think you are saying that your TDEE is 2000 calories allowing for your exercise which is let us say 300 calories, but you are restricting yourself to say 1300 calories intake (i.e. 1000 calories net of your exercise).

If your TDEE is 2000 then I think 500 is the right level for your fast day.

The health benefits of 5:2 fasting, considered separately from weight loss, are a vexed area because it is all so new. So it even harder to say whether you will get the (unproven) health benefits of 5:2 fasting when you are continuing to restrict on feed days. Personally, I think there will be proof in due course of real health benefits from 5:2 (aside from weigh loss) and that you would still get those benefits in your situation, but that's just my opinion!

[carorees]

Another consideration is that you say that you are eating 1300 cals until you get down to your target weight. I wonder if you are aware that your body will try to regain the lost weight once you stop eating such low amounts. Because your metabolism may have slowed by eating such a lot below your daily needs. Unless you are planning on eating around 1300 cals a day for at least 5 years, I think you need to up your metabolism. Eating up to your TDEE on non-fast days plus the two fast days will, hopefully, do this. So my recommendation is not to restrict calories on non-fast days and to try to average your TDEE over the week's non-fast days.

Thank you both very much for taking the time to reading and reply to my question.

Yes, dominic, I am actually consuming usually around 1000-1200 calories per day. With the added exercise (as calculated by the Lose-It app - not sure how accurate it is; WAY off from what my exercise bike calculates, but pretty close to what my rowing machine calculates), that keeps me at or usually just slightly below 1000 net per day. Using the various TDEE calculators I have found online, my TDEE is currently between 1960-2230, depending on the activity level I select (I seem to fall right on the "crack", so I think using 2000 as a ballpark figure isn't too far off). For the most part, in terms of counting calories, I don't obsess about it. I don't worry if I'm several calories too high or low, I just want to be sure that I'm in the general range of 1000 net calories per day on average. So far, it has been working great for me and I am a little worried about switching plans right now - "if it ain't broke, don't fix it!"

Carorees, your comment about metabolism, though, has me really thinking about this! I had pretty much decided to just continue with what I am doing for the present (i.e. calorie restriction every day, and no fasting) and switch to one day per week fasting once I reach my weight goal for maintenance and the health benefits. But now I'm not so sure. I will have to do some more research on metabolism, to try to figure this out. Thank you for pointing this out to me as I certainly don't want to do all this hard work of losing weight, only to have my body's changed metabolism undermine my efforts!

[carorees]

Yes, I recommend you read up about why we regain weight after dieting. Here is a thread which I started after reading some of the science about it:
viewtopic.php?f=10&t=395
It's fascinating stuff!

[janeg]

Hello Ahroo,
Caroline and Dominic have pretty much covered the sciencey bit! From a personal point of view, I started off 5:2ing with having 1200 cals on feed days.Worked that out with some calculator thing that said to lose 1lb a week that's what my daily cal intake should be. Nothing wrong with that and I lost some weight. Exotic holiday ( not great food though) Christmas and New Year intervened and back on 5:2 in Jan. This time with no real restriction on feed days. What do you know?- weight still coming off at the same rate!
And I can have Nutella and marzipan and other wee nibbles.
Happier Jane and more likely to stick to 2 days.