A nice balance between sophistic and serviceable recommendations in response to the OP.

To the OP, if you really think that your weight is a problem, then its best to consult at least a couple of medical professionals (both about your current health and any recommendations for change). I suggest a couple because you will find zealots on either side of the myriad "what's healthy" debate.

The only suggestion that I will assert is to stay away from simple sugars for the purposes of weight gain. First, simple sugars are not really efficient in meeting your goals and, second, they are associated with cognitive decline and affective maladies.