My Son Is 22. He Has Gained Roughly 48 Pounds

My son is 22. He has gained roughly 48 pounds since graduating high school in the spring of 2012. He has not tried seriously to lose weight and now we noticed he perspires a great deal when doing simple activities, standing around or even while eating. In his last physical exam his heart and blood pressure were normal, his liver numbers were slightly elevated but no other concerns. He is on medication for ADHD, switched from Intuniv to Vyvanse in the spring. The perspiring has us concerned along with the excess weight. He is 5-9 and weighing 210.