I kind of felt like that when I started (10 months ago). I'm still a bit overweight, though no longer a clyde (getting ready to break 190 in the next week or so at 5'10"). I really think that feeling, however, was self induced and probably more created by the fact that I didin't know ANYTHING about bikes. The first place I went tried to send me a hybrid where I was sitting upright saying that if I was comfortable I'd ride further. I'm sure that's true to an extent. But not what I wanted. The second place wanted to sell me a Kona Dew. I passed on that as well and got a mail order Ibex flat bar road bike. It's really a road bike without the drops (which I wish I had now)
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Since, I have been to the second bike shop for tune ups and asking about bikes and wheels etc. They even invited me back to watch them overhaul my bottom bracket this weekend. We started talking about a new wheel set and bottom bracket and as we talked they recommended that I don't bother upgrading anything on my cheap bike. Just keep it serviceable and save up for a new bike. They have done good work and have been very friendly and helpful. He suggested a Jamis Quest and I am intrigued. About in the right range for $ I'm willing to spend for my next bike.
Now, just trying to figure out how to pay for it
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So, short story long, maybe it's your own insecurities you are feeling and if you make an effort to reach out to them your experience may be different. Or maybe not...