The entertainment website Hollywood Life called her "scarily, skeletally, stick-thin," adding, "That's not how the human body is meant to look."
Swanepoel revealed her skinny frame while modeling the lingerie line's new swimwear at Los Angeles' Mondrian Hotel. With stick-thin legs and a hollowed stomach, the once-curvy model stood out among her fellow Victoria's Secret angels.
Swanepoel, a 22-year-old South African, looked significantly skinnier than in photos just two months ago, when she was the face of the company's Valentine's Day campaign. Her most recent modeling card from the agency IMG says she wears a size-8 dress, but she appears much smaller than that.
Swanepoel, who recently landed the cover of Victoria's Secret 2011 swim catalogue, has become one of the label's most popular models.
Perhaps her busy schedule's responsible for her dramatic weight loss. In November, during New York fashion week, Swanepoel told ABCNews.com that she was having trouble keeping weight on.
"Actually, this year my problem has been more putting the weight on and getting muscle on because it's been really busy," she said. "I've been traveling around like crazy. I get skinnier if I'm very busy. I've been eating steak and everything, so I'm actually looking forward to eating some lighter food after this."
Swanepoel also reflects what appears to be a shift by the fashion line away from its traditionally curvy models, like Tyra Banks, Claudia Schiffer, Gisele Bundchen and Heidi Klum, toward super-slim girls like Brazilian model Alessandra Ambrosio.
Victoria's Secret came under fire last year after Ambrosio appeared alarmingly thin, with ribs and pelvic bones protruding, during a swimwear shoot in St. Barts.
Even though she had her first child, Anja, a year and a half before, a photo of her next to two plus-size models showed her slight frame.
At the time, Ambrosio said she saw herself as a curvy girl.
"I'm very lucky to work for a brand that wants women to be healthy," the Daily Mail quoted Ambrosio as saying. "You need to be able to fill out the bra and the panties, so yes, I'm a curvier girl."
Standing next to Swanepoel at the recent Mondrian Hotel shoot, Ambrosio did appear curvier.
Last year, during a pre-Valentine's Day event, Swanepoel said food was the way to her heart.
"Usually my boyfriend cooks for me, which I really love," Swanepoel said, adding that pasta always wins points in her book. "It's really sexy."