The trailer shows her knocking herself out in spin class, waking up, looking in the mirror and saying: "I'm beautiful!"
She goes on to apply to become a model and enter a bikini contest.
Reaction to I Feel Pretty, which also co-stars Golden Globe winner Michelle Williams, has been swift.
On Twitter, Kiwi comic Rose Matafeo asked why the film hadn't been made with Will Ferrell, Jack Black or Vince Vaughan.
Others were angry with the message the film seemed to be trying to portray.
Writing for The Independent, Kate Leaver called the film's premise "clumsy, self-defeating (and) tone-deaf".
"Schumer is still blonde, able-bodied and well-dressed, with all the trappings of Western beauty standards," wrote Leaver.
"So this idea that, both in this movie and in her real life, she is some kind of grotesque outsider who dares to rebel against Hollywood aesthetics with the circumference of her waist is flawed from the beginning – and insulting to anyone her size or larger."
She called the film "so offensive and morbid it's frankly exhausting".
Schumer is yet to respond to the outcry. She promoted the film on Twitter with the phrase, "Change everything, without changing anything".
I Feel Pretty is due for release in June. Abby Kohn and Marc Silverstein directed the film, their debut.