'Twilight' Hotties: How We Stay in Shape

Stars of "The Twilight Saga: Eclipse" -- Kellan Lutz, Ashley Green and Jackson Rathbone -- gave "Extra" a few of their tips for staying in shape.

"I think the biggest thing is that I drink tons of water," Lutz told "Extra." "I think water helps your diet, as far as you aren't hungry all the time, so you will not eat big meals. And it's just great for your body. A lot if people think that you'll lose the water weight if you cut water out. But what that does it's like a sponge -- so it holds onto the water that you have. The more hydrated your body is, the more it flushes out. So I always drink a lot -- 12 -15 bottles of water."

For Greene, she likes a little healthy competition to get her going. "When we were training in the gym, we would go in at different times but had the same trainer. So we would always try to see who could do the most push-ups in a minute and who could run the quickest mile. It made the working out not as tedious and kind of a friendly competition."

See candid shots of the "Twilight" gang!

Rathbone has a brand new technique. "I was wearing my cowboy boots. I'm a boot guy, what can I say? I'm not gonna wear tennis shoes just to workout," he laughed. Lutz added, "These magic cowboy boots that [Rathbone] works out in. He can do anything and everything."

"When we shot the fight scenes, I had to wear cowboy boots because my character wears cowboy boots," Rathbone explained further. "He's not going to change his shoes to go fight; he's a vampire. So basically, I decided I'm going to fight training wearing the boots, I'm probably gonna end up wearing them in the film."