Actually laxative abuse can cause the body to hold onto to more fat and fluid (edema). It severly alters the electrolyte levels. Potassium can be lost in great quantities (harmful to heart & kidney). People usually suffer from dehydration. One famous Laxative abuser I just learned of in a recent Historical Film was Hitler. He actually had a lot of GI Tract problems and used laxatives daily.
I would not use laxatives. You can try Psyllium husk fiber to keep you regular. Liver strengthening herbs and olive oil can help your liver to release enough bile to move the stool and keep you regular.
Those are just a few suggestions, I do not know if you are at all constipated. If you are just curious about laxatives, I would say, no, they do not help one to lose weight in the long run.