Dont worry you will definitely lose weight. I mean your going to be in an extreem calorie deficit be careful. Also with something like that your body is going use some of your muscle mass. Dont you think something like alternate day fasting would be better or just 48 hours every week?
I do rolling 46s and every single day I have a giant 20 oz coffee with 100-120 calories of grass fed butter, occasionally a 100 calorie spoon of coconut oil also and I use half and half plus truvia.
Losing plenty of weight and I am able to get over 30,000 steps in plus weight training 4x a week.
Do not complicate it. Just fast. If some one wants to tell you a single 100-300 calorie coffee a day is not a fast then who cares. You’ll lose weight.
I have never tried it, but theoretically, if there is no sugar in your oatmilk, I do not think it would effect much except possibly autophagy (but I have heard even black coffee can effect that). There is a video somewhere of Dr. Fung saying not to panic if you accidentally eat a bite of food while fasting, because the insulin response will be so minute, that most people will be back to their fasted state within a few hours. I would imagine the oat milk would be similar, although if you are constantly intaking small amounts of calories throughout the morning, it might make the fast a lot harder. I am just hypothesizing though. Lots of people drink bone broth throughout a fast, which also has small amounts of calories.
Sounds like it could make the fast harder and could even interfere with the release of all that extra Human Growth Hormone beyond day four. That right there is what protects you from losing muscles. It may end up working like OMAD with extreme caloric restriction.
Just my hunch, but sure you can do that and you’d probably see results. Not sure it would be easy. For me, I suffer from the ‘appetizer phenomenon”. If I eat only a little it just makes me more hungry and harder to continue.
So in that way, have you looked into the 500cal style short term plans? They usually put an emphasis on protein and it helps if you’re also wanting/needing to workout.