Hello!
Good to know that you have calculated your BMI and want to lose 50 pounds. You need to go to a dietician and plan a neat diet chart with a balanced diet with predominant protein, fiber rich carbohydrates and complete restriction to sugars, chocolates, desserts, ice creams, deep fries, junk food and fast food.
I would suggest you to do a sustained cardio for 30-45 minutes continuously along with it and change in lifestyle like extra walks, errands to grocery, walking while talking on phone, walking and moving while cooking etc.
With sustained proper diet and intensive continuous cardio you will lose weight over a period of time.
Take care!
Oh by the way i have been using my treadmill to exercise. 15 minutes at 3m in the mornings afternoon and evenings. Plus i have been getting myself more active in what i do, like going for extra walks when i can, carrying stuff around on errands and basically trying not to say at one place too long.