I think that if your anxieties centre around people's immeadiate perceptions of you (and to some extent this is the crux of all our problems) then perhaps improving your appearance would help, but I don't think that if you suddenly became a supermodel your worries would dissapear, its more complex than that.
PLUS supermodels (male or female) are not everyone's idea of good looking. What may be good looking in my eyes is ugly in yours...
In my case yes some small worries were about my looks, people always said I looked miserable and tired/ill because I have dark circles under my eyes and never smile. Generally improving my confidence has helped me smile more - and everyone knows that a smile is friendlier than a frown. So improving things from the inside-out has helped two fold: get confident with what you have, then you emit this confidence naturally through your general posture and facial expressions, then you may even gain more confidence when people assume you're already happy and confident when you're only halfway there. Does that make sense?
My sister recently had a nose operation because hers was slightly bent. When I met up with her I have to admit I didn't notice her nose was different at all, but I told her she looked happier and healthier because she was smiling SO much more, she refused to believe me of course. So yes, for some it works that way. Personally I'm happy with myself, even thought my nose sucks and is much worse than hundreds of people who 'fix' theirs. :roll:
If you've become unhealthily obsessed with certain aspects then changing those offer some relief sure, but its worth recommending less drastic options first.
So we all know that initial impressions do count, but only for 0.0000001% of your overall personality. Its the rest that matters more, IMO.