I was told it doesn’t make a difference as they are actually measuring your uterus hence why they measure from your pubic bone and feel for the baby
If you’re hungry before then definitely eat :) it won’t make a significant difference, and keeping yourself fuelled is definitely more important x
I don’t think it really matters, the bump measurement is really not accurate at all and such an old method. I measured on 55th centile the whole way through my pregnancy from when they started to measure bump but ended up giving birth to a small baby below the 5th centile, the scan was the only semi-accurate way of picking it up x