There are two sets, this one for the Slim Bodybuilder, and another using the same textures for the "normal" Bodybuilder. The two sets have different waist dimensions since the two forms of the Bodybuilder are of different sizes.
If it is the mesh itself that is causing the problem, the problem is probably with the top mesh you are using. An early version of the Slim Bodybuilder top mesh tended to cause this issue. Since Body Shop now includes body and hair meshes with packaged Sims, it is now an increasing risk that this old version will be proliferated. If you are running the PC version of The Sims™ 2, then run
Sims2Pack Clean Installer of
Delphy's Download Organiser and check for duplicate meshes.
It should also be noted than certain low-end video cards and drivers may also be causing this issue. Try increasing your in-game video settings to high, this may resolve the issue. If you have a low number ATI video chipset, such as the X200 or X300 series, it will most likely require installing a more modern and more powerful video card to over-come the bug.