Fatigue on Tirzepatide

I took my first shot last week, and have been fortunate to feel some appetite suppression as well as minimal side effects, just a little nausea day one and two. I have seen many posts/comments about fatigue while on tirzepatide, and my question is this: Is the fatigue feeling drowsy or sleepy after taking the shot? Like a response directly to the medication injected?

Or, is the fatigue more a sense of low energy resulting from low calorie intake over the following days? I know people say they struggle to get 600-700 calories in, others barely making 1000-1200. I've been lower energy for the last few days, and I think it's due to lower calorie intake in my case. I can stay awake fine, but I don't have the energy to exercise. I'm curious what fatigue has felt like for others and how you've managed it.