Kate Upton
Kate Upton arrives for the 50 Years of Beautiful broadcast special show in Los Angeles [Reuters/David McNew] Reuters

Critically-acclaimed fitness expert and celebrity trainer David Kirsch revealed to Elle's Kristin Tice Studeman the Sports Illustrated Kate Upton's diet and workout routine. There are still tons of women who envy Kate's body type, even though she has received criticisms, because she is neither skinny nor fat.

According to Kirsch, Kate's diet secret is the habit of eating healthy combined with intense secret training. He said that Kate sticks to her diet. "She does a few egg whites with spinach for breakfast, and when she wants to, she does a 48-hour-cleanse."

"She has a very good sense of how she needs to eat for her body."

Kirsch further revealed that Kate isn't necessarily on a strict diet. However, she doesn't eat food that contain gluten ingredients. "I don't have her on a specifically gluten-free diet, but by nature of what she eats, it is gluten-free." He said Kate stays away from "sugar, alcohol, and processed foods."

As for Kate's exercise workout, Kirsch said she does an extreme and intense circuit training which involves exercising with resistance bands and stability balls. Kate also does lateral lunges to tone her inner thighs and boxing for her arms.

"We do three or four circuits and change them up a lot."

"There's lots of core, butt, and thigh-shaping and toning."

In the movie "The Other Woman" which Kate recently starred in, Kirsch said he trained and worked intensively with the blonde supermodel. "Depending on where they were shooting, we did five to seven days a week, usually pretty late at night for 60 to 90 minutes."

"It was very, very intense."

"It served two purposes: distressing and toning."

Kirsch started working with Kate in August 2012, he revealed in an interview with Shape.com. He worked out with Kate to prepare her for her second Sports Illustrated Swimsuit Issue cover. "Kate is the consummate professional, focused and disciplined and did whatever I asked of her."

"She's the best client a trainer could hope for."

Kirsch has also worked celebrities like Heidi Klum, Faith Hill, Sophie Dahl, Bridge Hall, Ellen Barkin, James King, Liv Tyler, Kerry Washington, Anne Hathaway, Karolina Kurkova, and Linda Evangelista.

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