42y, lifting for over 16yrs, OMAD for over 8 years. For health benefits but also to keep body fat in check i’d like to do 1 longer fast once a month (and OMAD during the rest of the month). What would be the best duration of such fast assuming i want to do it every month?
There is general no-issue with fasting and lifting. Meaning when you do reasonable fasts your muscle do not eat themselves(as generally believed). Lifting while fasting is certainly not going to cause muscle growth and if you’re 48hours into a fast your lift strength will be noticably reduced. But once you eat normally gain your strength comes back in full force especially if you been lifting fasted.
As long as you do some form of working out (I usually do some HIIT training on a rower for about 30 minutes), you shouldn’t see any muscle loss during a prolonged fast.
I know a lot of guys that are cutting up for shows that do a 5 / 2 (5 fasting, 2 non) or 4 / 3 split when gearing up for competition.
Since you’re not taking in any protein you’re not capable of building any muscle, but you’ll start to roll into ketosis about 48 - 72 hours into your fast and start to use your fat as fuel.
If you’re already doing OMAD you could always switch to a ketogenic diet for a few weeks and see how that makes you feel. Generally shorter fast benefits are more so getting you into ketosis, and kind of resetting your digestion.