i think you cant really change the shape of your hipbone if it is narrow and straight then nothing will make it wider but a smaller waist can give the illusion of a wider hip to waist ratio you could try working on your waistline?
First of all, exercise helps tone your body. If you do weight bearing exercises to tone your gluteus maximus you will tone and gain muscle there making it appear fuller.
Whether you lose, gain or maintain your weight while exercising really depends on your diet and not exercise alone.
Secondly, eating sugar is the biggest mistake you can make. Not only is it unhealthy for you but it will also make you gain weight in areas that you do not wish to gain weight.
My suggestion : start weight training. doing exercises such as squats and lunges are a few of the many things you can do to make your glutes look fuller.
... and what if you want to loose some there? any particular exercise?
and to the original poster, yea just sit for as much as u can, that's what i did for some months(not that i wanted to gain wait but just was way too lazy) and now i wanna cry...!! :(((