As the time is the constraint for you and you are very busy in your work the best exercise is skipping for 20 minutes everyday in the morning and jogging, running or swimming for an hour on weekends.
Select an exercise for 20 minutes on workdays before you shower which will sweat you out and you will be able to lose some 200-300 calories, start it slowly and with increasing stamina and endurance you will be fine. Have a healthy breakfast and carry salads and fruits to your work place for snacking and avoid fast foods and junk food.
I have a workout training video, where you have to put in stats and it guides you through appropriate workouts. Do you think this is going to help?