You fat? I'll assume you're a bit chubby. Don't wear a tight shirt, and wear stripes and dark colors. Go with nice shoes, a few bracelets or a watch, possibly a necklace, but it can't be too big, or a choker necklace.
Chubby to me is slightly chubby cheeks, a tiny bit of a stomach. No abs, and it's not completely skinny and flat. Go figure.