<human>: Can you give me the gist of the text in a nutshell?

I've (21F) been dating my boyfriend (20M) for almost 9 months. I love him very much, he's quite special and I intend to spend a long time with him etc etc. He is 5'7 and I assume well over 200 lbs. I am 5'6 and 125 lbs. All of his weight is in his belly...and at his age it doesn't seem healthy for him to have such a round, outward beer belly. He has HORRIBLE eating habits and does not exercise. That is what ticks me the most about the situation. 

Sometimes I lose physical attraction towards him, like when the belly is pressed up in my back (lol). I know personality is key but physical attraction is definitely important too. I just don't want to see him continue to gain weight, and I think it's a big insecurity of his so I don't know how to mention it. Or should I not mention it at all?
<bot>: BF has big beer belly/is overweight which he is insecure of but does nothing to fix it. Want to help him get to where he wants to be but don't know how to talk to him about it.