Meeting up with a friend (35M) who gained a lot of weight help me (35F) not say something stupid

I (35F) have been thinking about reaching out to and hopefully meeting up with an old friend (35M) that I used to be really close to but lost touch with. I hate that I'm asking advice on this because it's so superficial, but as someone who's had too many a foot-in-mouth moment, I think I could use it. Basically: he's gained a bunch of weight, and if it comes up when we meet, I don't want to say something stupid. Sure you might say it's not going to come up, but he was a total gym rat who really cared about how his body looked, like to the point where it would come up in conversation all the time. If I'm dealing with the same person (and maybe he isn't that guy anymore!), it's gonna come up. I'm not a complete idiot and I won't be the one to mention it, but if he were to say something like I know I don't look the same, how would I respond? Someone must have been in this situation before; a ton of people look really different after their 20s.