While you can always use simple adjectives to describe someone, you might want to try a few of the following words for specificity or variety.
Words to Describe the Body
Gaunt -- Too skinny, very thin
Wiry -- Thin and muscular
Petite -- Small and thin
Willowy -- Thin with long, thin arms and legs
Lean -- Slim and long
Stocky -- Short and thick
Curvy -- A body with a smaller waist and larger hips and chest
Barrel-chested -- A body with a large, rounded chest and stomach
Hefty -- Large or heavy
Sturdy -- Large and strong
East Bay ESL is an English language school for adult students in the San Francisco East Bay.