First of all the age should definitely not be an issue. The weight? Why don’t you go and see for yourself. That being said, you’re 26 and you haven’t gone out yet?! That is something that might be a strike against you. Don’t add any more strikes by being the guy that said no after saying yes, but before meeting.
If not for anything else, it’s time you get your feet wet. What’s the worst that can happen?