I've probably outstayed my welcome here, but...

At the risk of becoming a serial forum stalker, I would appreciate a little more advice please..

I've come up with what I think is a very funny little piece about how we view people with really fat beer bellies. Now I'm pretty blobby myself, so it's not a cruel bit of monologue, but if I were to joke about, for example, obese women and there just happens to be some in the audience, do I just look mean and cruel and lose the audience sympathy? Or is that something that a comic just doesn't consider when preparing a set. Obviously I wouldn't be actually targeting the poor lady, but just the fact that she was there, would it make my joke fall flat?

I think this really depends on what you have written and how it's delivered, if it's funny you can get away with saying pretty much anything, but I would avoid anything that may alienate your audience.

I used to do a joke about English girls not being pretty, it used to get a laugh, but as sometimes people don't realise I am a character and it was tongue in cheek I just started getting a sharp intake of breath from the audience and a few groans, so I changed it up and still use a similar line but now make it more self depricating towards me.

You can see my act when I still did it here: http://www.youtube.com/watch?v=I7cWdZFsP-Q