Do you lose weight if you are snusing/snuffing?

Not particularly. Nicotine does have some appetite suppressant effects, but it is not a weight loss product. People who become dependent on it do have a problem with eating more and gaining weight when they try to stop. It is not healthy and is associated with mouth, tongue and throat cancer. If you have a weight problem, proper diet with reduced calories and increased exercise remains the best way to lose weight.
Maybe. Maybe you will but you're still at risk for oral, laryngeal, and esophageal cancers which if you get cancer will definitely help with the weight loss.