In fact, the actor wears a fat suit and prosthetics while in character.
Yes, you read that correctly.
you could watch the whole thing go downhere.

Ron Batzdorff/NBC; Allen Berezovsky/Getty Images
Sarah Paulson inAmerican Crime Story: The People v. O.J.
Simpson
Paulson loved the wig she donned to play O.J.

Colleen Hayes/FX; Robin Marchant/Getty Images

Macall B. Polay/HBO; JB Lacroix/WireImage

Will Heath/NBC; Axelle/Bauer-Griffin/FilmMagic

Michele K. Short/FX; GP/Star Max/GC Images

Joe Lederer/Netflix; Roy Rochlin/FilmMagic

Jennifer Clasen/ Amazon Studios;

Ray Mickshaw/FX; Jason LaVeris/FilmMagic

Ursula Coyote/AMC; Frederick M. Brown/Getty Images

JoJo Whilden/Netflix; Stefanie Keenan/Getty Images

Everett Collection; Todd Williamson/Getty Images

Curtis Baker/Netflix; Neilson Barnard/Getty Images

AMC; Paul Archuleta/FilmMagic