I see a lot of exercise reccomended ITT, but just remember that it takes an hour to "burn" 300 calories walking, but under a minute to eat a donut. Dieting is your battle. Also, doing a little exercise (5 min walk) everyday that you can keep yourself doing consistently is WAYY more important than the 2 hour gym sesh you hit twice then get demotivated and never do again
(This is coming from someone with no experience losing weight, so take it with a grain of salt)
I go road cycling a lot. That burns more than 600 calories an hour. Just one 3 hour ride per week offsets almost as much calories as eating in one day does.