The FastDay Forum

Im Fasting today, and have a spin class after work. Im wondering does anyone ever go over their calories on a fasr day when they are exercising? if you went over approx 50 would this be the fasting day destroyed??

50 cal - no that is not going to break the fast to pieces! Just keep it as low as you can.

If you read further into 5:2, you'll find 500 cal is kind of an arbitrary number - 1/4 the cal an average woman should eat. Those who are above average weight/height could actually eat a bit more based on their TDEE, but as you lose weight, you find that number can actually go below 500!

According to Dr.Michael Mosley in his book the answer to your question is that you don't earn extra portions by exercising and he explains why. But as Debbie says it is an arbitrary number
I have just started the diet and had a great number of questions being diabetic.

[Moogie]

Simply put, no you don't 'earn' extra calories for your fast day by exercising. However, going over by a little won't ruin the fast. I allow +/-10% and don't stress over it. During the Christmas break I pigged out most of the time and had my fasts on about 650-700 cals (including a choc or two!) and came out half a pound lighter on the other side after the 2 week break!

Think of the exercise a s a bonus. If you cave calculated your TDEE it will have asked you what your exercise level was. The TDEE will then give an amount based on that level of exercise so I'm afraid its already calculated in.

[carieoates]

I often have 500-600 cals on a fast day as My TDEE is 2357. 575 is a quarter of my TDEE. your TDEE takes into account your activity levels however I do find it difficult to eat 2357 on my feast days unless I have wine and I'm not a chocolate and sweets kind of a gal.

I shall differ from those above - if you are exercising hard (and I don't know how hard spinning is, I'm afraid) I would recommend having a post-exercise feed of at least a good proportion of the energy burned available to supply nutrition to damaged muscle tissues and replace some glycogen - otherwise you might start losing lean tissue mass. If you save all your fasting calories for after your spinning session you will probably be ok, but you might not be able to work as hard as you are used to during the session.
Longer, multi-hour, sessions I tend to treat as extending the fasting period because energy stores, hopefully including fat, are being depleted at an enhanced rate. I personally allowed for this by increasing my fast-day intake and it seemed to work - but your experience might differ. Do the experiment & report back! Good luck...

Thanks for all your replies, with my TDEE being around the 1600 mark - I think I will stick to 500! spinning was extremely difficult, but I feel more energetic on fast days when exercising! Which sounds strange! But it's good as keeps me busy! Also have had plenty of water and green tea which has eased the hunger! In fact, don't even feel hungry! It's great! Thanks again!

I don't think you should count exercise calories on fasting days, but as someone else said, consider it a bonus. I like to do mild to moderate, but not strenuous exercise on my fasting days as it tends to decrease my hunger. This might be psychological rather than physical as it's something to do that takes your mind off food. I often do about 200 calories worth of walking on the treadmill or outdoors on a fasting day, but that doesn't mean I allow myself 700 calories instead of 500. Keep up the fluids especially if you exercise.

Mary99 don't substitute cals for your fast days. I did and it doesn't work - you might as well be just on a low cal diet then. I do my marathon runs by keeping my 500cals until about 90mins before I'm due to run. I then eat 2-4 jellys to give me a slight sugar boost as I had one bad experience of nearly passing out with low sugar levels. THen cup of tea and to bed. I have a TDEE of similar to you when not exercising but if I put in moderate exercise 3-5 times a week it raises to 1800 which means that I should only have 450 or so on fast days but I'm usually around 500-530 and I still lose