What is the reason for wide hips? How can I reduce it?

Mostly because of the usual bad habits. Just like some people sit all day at work and continue to sit in front of the computer when they get home. After a long time like this, the crotch becomes wider and wider.

To improve the situation, I think you should pay attention to your diet, do not eat greasy fried food, eat more fruits and vegetables. When you work more get up and move around, after work more fitness exercise, like running, swimming, playing Tai Chi, dancing and so on are available.