How to reduce my bully? Now a days it has become very big, are there any diet I should?

Caloric reduction. Reducing weight is a universal problem with no easy answers. The short answer is reduce the amount you eat and exercise more. You may start out by writing down everything you eat for about a week and try to reduce you intake by eliminating unhealthy foods.
See Family Doctor. This is a common problem today in america and solved or improved by experts in this area. I would start with your family doctor and see what he/she has to advise.