I disagree.
I am totally for weightlifting. A toned physique is more attractive than being too thin, or worse, obese. However, I know a ton of guys who are cut like you wouldn't believe, and they have NO success with women. Conversely, I know guys who are not cut...mostly thin but some are a little hefty, and these guys bag some of the 9s and 10s we all clamor over.
THe most important thing is confidence. One way to build confidence is finding something you're good at and sticking to it...enjoying it. If you don't enjoy weightlifting and are in ok shape as it is I wouldn't do it. Do something else. Last time I heard musicians got more girls than bodybuilders....although both got more than lump lazy guys who do nothing.
Just find something you enjoy. As was said before on another thread, the key to attraction is charisma, and the key to charisma is being happy. Be happy doing what you like.
The rest will follow.