Does marijuana affect you from building muscles or losing weight ?

Maybe: Males who use marijuana have increased levels of circulating estrogens, which of course, compete with endogenous (your own) androgens for binding sites in tissues. If you're serious about body building and weight training, you should want to be as healthy as possible, so using drugs is not a good choice. Of course, the "munchies" usually result in carbohydrate excess, which isn't always good.

Yes: Initially there is interference to growth hormone production and testosterone which will interfere with muscle building in addition unless appetite is controlled and nutritious foods are consumed instead of junk foods, bodybuilders and fitness models who use marijuana may find that they are constantly involved in a battle of the bulge.