If you are a heavy-set, it's tempting to hide under over sized clothes. It doesn't work because it makes you look sloppy and even bigger. Best thing to do is to visually slim down yourself by keeping the eye away from your bulk. For example, contrasting colors will break you in half making your large middle section stand out. While darker colors and a monochromatic scheme will flatter your shape.
Infographic Source: beckettsimonon.com