I just switched from running to cycling and I have found the weight loss to be profound - mostly because I like biking a lot more and have a harder time finding excuses not to ride. I can bike after a big meal, I can have a glass of beer at 4 and ride at 7, I can ride at 6 in the morning. All of those would have been excuses for me as a runner. Anyway - I would ride as much as your schedule allows and track your progress on the scale. I try to go for an hour at minimum, but do what you have time for. And as the OP suggested - watch your diet as well. Good luck!!