ok - dumb ass question time!
If i'm doing 3 days normal eating (watching my macros) and 24 hr fast, then 3 days normal eating - i'm guessing that i dont need to make any changes to my macros for the 3 days to compensate for not eating for 24hrs?
If your goal is fat loss, you need a calorie deficit. So if you're doing 3 days eating, 1 day fasting, over that 4 day cycle you need an overall deficit, and a healthy one at that, since progress is going to be much slower than if you were running a daily deficit. (This is why I think 24hr fasts are sub-optimal for those looking to get lean reasonably fast).
My goal is fat loss and lean muscle mass gain - which is why i'm trying this and not bulking and then cutting (i've been on a bulk for 4 months).
Unfortunately
some IF'ers have perpetuated this idea that it's possible to do both of these things at once as quickly as people doing one or the other, and the reality is it doesn't work like that. Even Martin Berkhan no longer does -20/+20 type recomps with clients, from what I've read, just a heavy emphasis on one goal or the other (so -40/+10 sort of thing on a cut).
If you want to lose fat, cut sensibly enough that weight is going down but gym performance isn't suffering, then worry about bulking later, otherwise it just leads to a lot of wheel spinning for most people.
My plan was to eat normally on the days i'm not fasting and make no changes based on the fact that for 24hrs i wont be eating - or should i eat more the day before i fast to compensate?
You'll just slow fat loss or even cancel it out overcompensating on your non-fasting days. Doing all sorts of calorie zig-zagging is just overcomplicating things. If you're going to 24hr fast 2 times a week rather than run a straight deficit, ensure your non-fasting days are definitely around maint. level and on your 24hr fast day, the meal you have to break your fast (e.g. at dinner time after fasting since dinner the day before) isn't essentially maint. cals in a single meal, since this misses the point entirely, e.g.
Day 1 = 2500cals (maint.)
Day 2 = 2500cals (maint.)
Day 3 = 2500cals (maint.)
Day 4 = 1000 cals (deficit)
4 days maint = 10,000 cals, actual intake over 4 days = 8500cals, so a 1500cal deficit which would in theory be the same as having a daily deficit of 375.
Most people run around a 500 cal deficit when doing fulll time cut, sometimes more, so obviously you can see which one will yield quicker results (as most people in the game want to spend a much greater ratio of time strength/size gaining vs losing fat).
The whole fasting thing is the icing on the cake - which was the point of Leangains in that 16 hours fasted was a decent amount of time to get the theoretical benefits of fasting combined with a regular approach to intake.
Stream of consciousness ramble blah blah.
