Keeping Kate’s Curves: How Upton sweats it out without getting too skinny

Kate Upton is showing a little less skin than normal as the face of the new David Yurman jewelry campaign, a job previously held by super skinny models Kate Moss and Gisele Bundchen. Adding the coveted campaign to her turn on the cover of Vogue, as well as two straight issues of Sports Illustrated, has further cemented the curvy Upton as the hottest model in the industry.

And its David Kirsch's job to keep her that way.

“I know and respect her body and her desire to maintain her shape. I love curves and I think as someone who is blessed with that as she is, it is my responsibility and my goal to tighten and get rid of the excess,” her New York-based trainer told FOX411’s Pop Tarts column. “Kate is the all-American epitome of the gorgeous curvy; she is the Marilyn Monroe of the 21st century. She is beautiful, she is accessible, she is sweet, she’s got curves, she’s got good boobs and she is every guy and girl’s dream… mostly.”

Earlier this year, Kirsch told New York Magazine his star client had drawn some criticism for being “porky” or even “fat” in her famous S.I. spread, but he insists such judgments are few and far between.

“The couple of friends of mine that don’t think (she’s got the ideal body) like girls with no curves, no boobs,” he explained. “Kate really didn’t have to work out ever, they can cover her body and just show her assets, and just be fine. But when I got her to where she was, she was like, this is amazing.”

Upton really wanted Kirsch to get ready for her role in the new movie “The Other Woman” alongside A-list stunner Cameron Diaz.

“I worked with her seven days a week for five weeks to get her ready for the shooting. She was looking the best she has ever looked, so now when she is a little off, she knows what she has got to do,” Kirsch continued. “I don’t believe in a lot of weights and I don’t use more than five pound dumbbells or 6-8 pound medicine ball. I do a lot of bands or ankle weights and high reps; she knows that I will always conveniently tell her to do more. (It’s about) keeping the reps high and the weight low.”

And according to Upton, no matter how hard or for how long she pushes it at the gym, those curves are not likely to budge.

“They are not going away, no matter how hard I try,” she laughed.

Upton is not the only one choosing curves over concave stomachs.

"It seems like the ‘brand’ celebrities are embracing (their bodies) and flaunting them," said JJ Virgin, author of the best-selling book “The Virgin Diet.” "Jennifer Lopez, Sofia Vergara, Jennifer Hudson and Beyonce. Ditto Jennifer Aniston, thin and fit. That is her look.”

Oscar-winner Jennifer Lawrence, who now ranks among one of the highest paid actresses in the world, has also repeatedly said her goal is “to look fit and strong – not thin and underfed.” Even while she was preparing to play Katniss Everdeen in “The Hunger Games,” her trainer Dalton Wong focused not on baring bones but on such things as stretching out her hips and her back with yoga and Pilates to make her feel longer and leaner.

‘I’m never going to starve myself for a part,” Lawrence told Elle Magazine. “I don’t want little girls to be like ‘oh, I want to look like Katniss, so I’m going to skip dinner."

Danielle Jones-Wesley contributed to this report.