Husband insists on "dieting" right now

He Did this with my first too. It's driving me crazy! I eat healthy and have only gained 5 lbs so far. but I'd like if he didn't have to talk about his diet all the time. To make matters worse - he's now talking about how much weight he's lost. 
Like come on, can't you be a little supportive and not shove it in my face when I can't be there with you? I'm totally supportive of him being healthy, but instead of doing it together (like after my first was born and I ran a marathon and he gained 15 lbs) he has to do it right now. It's just messed up and I feel like he's doing it on purpose because I can't do it. 
We already had one row about it. He totally didn't get it and just kept saying I didn't want him to be healthy. Obviously that's not it. Just explain to me why it has to be right now when to be honest I'll be gaining 20-25 lbs total and can only watch the scale go up.