How do I bulk up with OMAD?

It's purely going to be a reflection of your workout. You're going to have to work out with heavier weights, less reps to the point of fatigue, and that way you can maintain the muscles. You can't grow your muscles by not exercising. Exercise is the only way you're going to be able to actually enlarge your muscles. But here's the cool thing. When you do keto and you do intermittent fasting, it protects the loss of muscle. There's certain things that protect the loss of muscle, which is a kind of a survival mechanism. So if you do this and you add a good workout program where you actually really stimulate those muscles with the intensity that is needed. Muscles will enlarge, and especially you have to feed them the right things too.