I want to be thin and slim so what should i do? and i also want to remove my dark circles from eyes....

Healthy Weight: There is no magic. There are no fad diets that will work for you. The way to true healthy weight is through limiting the calories you consume; making sure that the majority of your calories are from proteins and only a little are from fats or sugars. Exercise is next. Regular moderate (heart rate about 130) exercise can burn off excess fats and sugars. Good hydration with that will help skin.

Be healthy: Rather than think thin and slim, you should be healthy, which means eat healthy, exercise regularly, live life in moderation, rest as much as you need and keep a regular schedule, and take media images with a grain of salt. (avoid social pressures).