What can i do or take to gain weight?

Exercise: Eat a healthy diet and do resistance training (weight lifting) to build lean muscle mass. Muscle weighs 4 times more than fat--so lay off the sugar and diet sodas. Avoid the desire to overheat and just get fat! too many health risks! if still having problems, consider talking to your pcp about potential endocrine (thyroid?) problems. Good luck. (lol-the picture shows one other way...).