I'm 36 weeks and have put on 8kg (started at 66kg). I've eaten when hungry but I've been lucky not to crave sweet things. I've exercised when I've felt like it. Sometimes 4 times a week, sometimes a big fat zero.
SIL is 20 weeks and already as big as me and she's not changed the way she eats and walks the dog every day.
So it just depends on the person I think and it shouldn't be an issue.
My Mum sometimes obsesses a bit about my supposed weight gain but she has issues on that score so I ignore her.
If you feel well and the baby is well then does anything else really matter? IMO.