Masturbation will cause you to lose weight if you expend a lot of calories, by doing it for hours. If you stop masturbating you will eventually have a "wet dream".
From your question I assume you are a teen or close to it. Anyway, as time goes by your nocturnal emissions will become less and less and probably stop altogether. If you have them very frequently, you could have a medical condition which should be addressed.
Let me have your comments.