I agree - 20 grams is just a limit to maintain ketosis.
Macros do not work well with IF/OMAD.
The hope (if someone is truly fat adapted) is that if you normally eat:
- 20 grams of carbs, 100 grams of protein and 200 grams of fat (2280 total calories)
on a regular keto day that then on an OMAD day you would eat:
- 20 grams of carbs, 100 grams of protein and 60 grams of fat (45% of 2280=1026 calories)
and your body would happily go get the other 140 grams of fat from your body.
Simplistic but the point is that you would still want your 100 grams of protein versus just 45.
Not a doctor - this is my understanding of how this all works.
I guess as a byproduct of this, you want to keep it in mind for your meal planning. If you have some keto casserole you normally eat on your 2280 calorie days - you wouldn’t want to just eat a 45% portion on an OMAD meal - not enough protein (i.e. you might not want to just eat 45% or your usual menu).