A body contouring apparatus and the method for using such apparatus is provided. The apparatus comprises a flexible rod, which has two ends and a laminar cross-section. The exercise device can switch between a rod shape and a ring shape. The exercise device has two connecting components, which are disposed at the two ends of the flexible rod, and at least one handle portion, which is female-connected to the flexible rod. When the two connecting components are connected to each other, the exercise device is in a ring shape; and when the two connecting components are not connected to each other, the exercise device is in a rod shape.