"Barstars"...OK, this is why I LOVE this site...I learn something new every day...
I could devote a month of my time discussing "barstars"...but to stay on topic.
I learned this from years of experience - it makes no difference what you look like or dress like, when you walk into a bar, half the guys wont care for you anyway (this is usually the half you find hot and attractive)and the other half will care for you (usually the half you have no interest in). But then not always.....
I know that the younger you are, the more important material things sometimes seem to you and to those who you perceive to be interested or "should" be interested in you.
If you walk into a bar and are unsure about yourself you project that every image to every person in the bar.
Some general advice - whenever you wonder why guys do or do not approach you in a bar ask yourself this "would I approach me?" based on what I was wearing/looked like/behaved. You have your answer right there. If was overweight I doubt I would want to wear a spandex bodysuit. Likewise if I spent hours in a gym and on the field getting a smokin' body then I prb would want to show it off if I wanted to attract attention or not.
If you feel good in designer clothes, then wear them. If you feel good in a white T and jeans wear that. When you feel good about yourself you definitely project it to others. One of the most attractive qualities I find in a guy at a bar (regardless of what he looks like) is the one who is smiling/laughing - not standing in the corner with his arms folded with a scowl on his face.
Some good advice has already been offered on this topic. The more you time you spend worrying what others think of you the less time you have to worry about YOU and what you want. Be yourself and if you dont' attract those who you think should be attracted to you, it's their loss and you they don't deserve you anyway.
If you don't like the way you look, then do something about it. My ex was a doctor, worked 6 days a week and still found time to train over 2500miles in three months to do the Hawaii Ironman.