There are few things in this world that bother me as much as people who complain but are not willing to make a change to fix whatever it is that is the issue. If you aren't willing to put forth any effort or make any adjustments, then you do not have the right to complain about the situation you're in. Effort breeds positive change and change produces character and quality.
As someone who has always found comfort in the gym, on the court, or doing something active, I know I take for granted the complete comfort I feel doing those activities. I'm not saying that some of the physically demanding activities don't burn or hurt my muscles, but, mentally, I'm comfortable doing what I'm familiar with. It makes sense that some people would feel uncomfortable or out of place doing these activities because A) maybe they've never done them before, or B) maybe their body isn't prepared for the physical exertion.
In regard to point B listed above, it's tough. I know it's intimidating to walk into a gym full of perfectly sculpted bodies, both men and women. It's scary to be the weakest one there, the skinniest, the chubbiest, or maybe the most uninformed. It takes a lot of mental toughness to walk into a gym, know that you need help, and not be afraid to ask for it. First of all, half your battle will be to learn how to effectively work out in your specific body. Second, you'll have to block out everyone else there and stop worrying about what they're thinking. If you feel as if they're watching you, they probably aren't. They most likely want the rack you're working
I saw a post online this week about a body-building couple who have been criticized for spending too much time in the gym and too much time spent counting their nutritional intake. It really goes to show that both ends of the spectrum of physical fitness will be criticized. You're never going to be the perfect size, weight, or have the right amount of strength to please everyone, so find one that you are comfortable with for yourself. Being comfortable in your own skin and not hating the body you live in every day, is in your control. It won't be easy, and it's not for anybody who won't make a healthy lifestyle a priority. But the first step is to stop the verbalization of your discomfort by complaining, and start to making a change. Actively working to make a positive change in your life is completely worthy of respect-- complaining and doing nothing about it, is not.