I am on the brink of diabetes and I'm over weight please help ????

see when i was 13 they gave me a pill that within the year i gain 50 pound (it was antidepressant ) and now that i'm about to be 17 i want to lose all the weight and get to down 160 i just weigh at 205 . i'm 5"5 , so does anyone have a diet plan i can use to lose all this weight and be back to be skinny again ????