Being plus size,and problems in wearing dress and health concious.?

im a girl 5ft 3 inch and over sized around 80-85 kgs.my fat portions are my thighs,butt and arms.this makes it really difficult to dress in style be it anythn to wear.once in a while i try the gmc diet and it kinda works.but 4-5kgs is not tht i have to loose...have to loose around 15-20kgs.could anyone help me with a perfect diet for each day ?