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There's a much talked about scene in the The Other Woman, starring Cameron Diaz, Leslie Mann and Kate Upton, where Diaz and Upton have a showdown in their bikinis. Upton does a slow, Baywatch-style run looking like a goddess, while an angry and jealous Diaz comes bolting towards her in a jealous rage. Both of their bodies' look pretty kickass in the movie (no surprise there), and left this writer thinking she should get to the gym in time for beach season. So to find out the latest on Upton's workout and diet routine (we know Diaz's secrets now, thanks her new tome, The Body Book), I went straight to the source, and checked in with her trainer David Kirsch. He's also helped the likes of Liv Tyler, Karolina Kurkova, and Heidi Klum get their rock hard figures. Here's what he had to say:

When it comes to Kate, what's the most asked question you get?

Everyone wants to know if she is disciplined with her diet and exercise and the answer is that she is amazing about the diet. She does a few egg whites with spinach for breakfast, and when she wants to, she does a 48-hour cleanse. She loves my Thermo Bubbles for snacks and my Super Charged Greens. She has a very good sense of how she needs to eat for her body.

You have her on a no-sugar, no-carb diet. How strictly does she adhere to that and how do you feel about the gluten-free craze?

It's sugar, alcohol, and processed carbs that we avoid. I don't have her on a specifically gluten-free diet, but by the nature of what she eats, it is gluten free. I have both my daughters on gluten-free diets and you can see the difference. They are only four years old old and it definitely changes their mood. You can see that for sure.

So...She's not even allowed the occasional one or two glasses of wine? Is that really that damaging to your fitness?

No, it's not going to kill it, but I need to at least put the fear of God or fear of something into my clients. There should be the guilt factor. A night of binge drinking can really undermine what you are doing. If you are on a shoot, you want to look your best and if you are drinking, you aren't going to be able to do that. I don't care who you are.

You have been asked over and over about her workout routine. How have you changed it since you started working with her?

We do extreme, intense circuit training. We do three or four circuits and change them up a lot. There's lots of core, butt and thigh shaping and toning. We work with resistance bands, stability balls, do lateral lunges for the inner thighs and for arms we do boxing. She has her own pair of boxing gloves and she will beat me up. She loves it! It's a very efficient way to workout and get your cardio in.

For the movie, I know you worked out extra intensively with her. How many days a week and what exactly were the workouts?

Depending on where they were shooting, we did five to seven days a week, usually pretty late at night for 60 to 90 minutes. I would have to get a babysitter to watch my girls and train her. It was very, very intense. It served two purposes: de-stressing and toning.

What do you suggest in terms of a workout routine for the average person (who isn't trying to get the cover of Sports Illustrated, but still wants to look good)?

Do a couple of high intensity circuits a day. You aren't going to be on the cover of Sports Illustrated or something, so the pressure isn't there. Make time for one or two circuits first thing in the morning. No one can tell me they don't have 10 or 15 minutes extra minutes a day. I don't believe it. You don't have to do 90 minutes.

Via .

From: ELLE US