Back when I was an art student taking figure drawing classes, I always found the very lean models more difficult to draw than the larger ones. When studying the human form, for me, rounder models were just more interesting to draw.
An old RISD classmate posted a neat link on Facebook: a photoshoot of various Olympic athletes by Howard Schartz and Beverly Ornstein titled “The Athlete”. These photos are a great example that strong, athletic bodies come in all kinds of shapes and sizes, too. I really like how the photographers took athletes from a range of sports and grouped them together with others of vastly different heights and weights. It's a great example of body type diversity and an excellent source of reference material for artists.
Hit the link for the whole shoot. Thanks to Jesse Smolover for the tip!