I'm not going to give anything away in this most excellent animated movie, but suffice to say, it's the future, humans have everything automated and processed, they don't exercise or eat real food and they're all fat (how did the Jetsons stay so trim?).
You can even see the progression of the human race over the centuries as they got bigger and bigger. The humans in WALL-E are so inactive they don't even realize they can stand upright. They drink a lot of their calories and everything is supersized, including the captain of the spaceship (voiced by my high school-era bud Jeff Garlin, cartoon visage at right).
(And P.S. to the mom with the yappy toddler behind us at the Muvico. Just because your child has functioning eyeballs doesn't mean he's old enough to attend a movie. The word is "shuuush.")