How do I go about this

So me and my partner celebrated 3 years on Jan 1st. Hes gone out tonight and come back cold and I've cuddled him to warm him up as he was moaning. Next thing he said just shocked me?

" I'm glad I've got a fat girlfriend to keep me warm but I cant wait for you to lose it so you look good again "

Like I've put a couple extra pounds on the last few months so I'm already insecure about it ( working on losing it and what not now)

But it's just knocked me? Like I understand about being honest and he already knew that I knew I was gaining weight but theres better ways to go about it isn't there?