I am overweight. With my DD, I only gained 15 lbs.
I am 4'10" and alternate between 155/160. At the beginning of my pregnancy with DD I weighed 160, and just before she was born (5 days in fact was my last OB appt) I weighed 175. One week after DD was born I weighed 155.
I was a borderline gestational diabetic, and my doctor thinks insulin reistance came into play. DD was born a healthy 6 lbs 15 oz. So no problems with her. In fact my Ob was expecting her to be larger and take a toll on my body. She was so small though, that we had to run out and buy preemie clothes and newborn clothes to clothe her for the first month, because all of her other clothes were SWIMMING on her. She is now three and has finally caught up, mostly in size, except for her waist, which is a size below (tops/dresses are a #t or 4T and pants are a 2T/24 months). However, for two years I got double useage out of most of her clothes, espically if they were Gymboree which runs a little large.
I was tested for Gestational Diabetes EARLY (around week 12 due to my family history) so for most of my pregnancy I watched what I ate (however that did not stop me from having a mint chocolate chip kid's cone from Baskin-Robbins once a week). I wasn't perfect, but I watched what I ate.
I never had morning sickness, however my appetite went way way down. I used to joke that my husband was the one "eating for two" because he'd often finish my meals.
ETA: For most of my pregnancy I gained NOTHING. I started having biweekly appointments earlier than most, due to the gestational diabetes thing and my OB had me see a high-risk OB as well. So every week I was seeing either my reg Ob or the high risk OB. Anyway, every week the weight stayed the same. Until the last month and a hlaf when it climbed up. We actually cheered when I went up 1 lb.