I realize this is just my experience and I don't know if there's any scientific data behind it but in case this might help someone I wanted to post it.
I apparently have become castrate resistant and have restarted Abiraterone about 4 months ago. This is my second time I've been on Abi and this time my SE's are much less severe than the first, expect for fatigue. I found that I was increasingly feeling fatigue to point I was having urges to take multiple short naps per day.
So, I started some investigations into this and landed on my prednisone dosage. I found that one reason prednisone is given with Abi is because Abi blocks cortisol production and prednisone is given to help replace that lost cortisol. One of the effects of low cortisol can be increased fatigue.
My MO had me on 5 mg/day which is what I had before when I was castrate sensitive but I saw that the normal dosage when castrate resistant is 10 mg/day. So I messaged my MO about this, who replied almost immediately (I love how responsive my MO is) that I should give it a try and start with the 10 mg. I started feeling noticeably more energetic very quickly, to the point I almost feel like my old self, albeit a 65 yo self. I relayed that to my MO and he's now bumped up my prescription to 10 mg. I don't know why more prednisone may be needed when castrate resistant or what my MO's thinking was to keep me on 5 mg. But I definitely feel more energetic. I'm actually back out getting in some runs on a regular basis now.