Is he a big man himself? I think that he may be insecure about his wife becoming more skinnier and more attractive (not trying to be shallow, but our world looks at the size of our tummies as a factor to gauge how attractive we are). He probably takes solace in that you'll just plump right back up.

My wife gives me crap about Atkins sometimes...but she's pregnant and has gestational diabetes, thus she is self-conscious about her belly getting bigger. Which she has only gained 10 lbs. and she's 35 weeks along. I think that she is genuinely happy for me that I am losing the weight, though. The crazy thing is, I've lost weight both times that she has been pregnant.