Exercise!
The two major behavior changes one can make to lose weight are to reduce calorie consumption and to increase calorie expenditure (aka “exercise”). The surgery only addresses the former. It’s silly to expend so much effort to change your eating habits only to neglect the other major method to lose weight!
Exercise does not have to be in a gym. Many people find working out in a gym or on exercise equipment to be boring and even punitive. However, the same activities, like walking and biking can be very enjoyable outdoors, especially when done with others. Activities like hiking, tennis, swimming and others are actually fun, and might not even seem like “exercise” at all.