The best protocol is one that you can sustain for a longer period of time. If you’re having a calorie deficit and busting your ass at the gym (after not going for a while) you might be in a body recomposition fase. Take pictures to measure progress.
If that isn’t the case you must be eating too much calories during the OMAD, try tracking them or switch to healthier options.
Why are you doing it for 5 days a week, any specific reason? Perhaps an alternate fasting schedule will work better for you? Could throw in some 48/72 to accelerate weight lose if it fits with your schedule.