How can a negative body image hamper exercise at a gym?

By embarrassment. People with a negative body image may feel embarrassed or intimidated by the "hard bodies" they see, leading to avoidance of the gym. Places, like curves, cater to older individuals trying to get in shape, and are not hang outs for hard bodies. Finally, swimming hides thi and can be enjoyed by almost everybody.
Camouflage. Use loose clothing. Long pants. There are lots of athletic gear that makes you look great. Avoid the tight clothing. Train your mind gradually. Is possible. Myself and many more are proof of it. Pma: positive mental attitude.