Tobey Maguire's Yo-Yo Diet

(AP)  Tobey Maguire has been yo-yo dieting lately, but it's work-related.

He bulked up to star as the web-slinging crimefighter in last year's "Spider-Man," then trimmed down to play a jockey in the upcoming "Seabiscuit," then had to get buff again for next summer's "Spider-Man 2."

"Coming off of 'Seabiscuit' and going into 'Spider-Man,' it's different physically," the 27-year-old actor told MTV News. "I had to put on some weight and I didn't have a lot of time to train, I just changed my diet and my workout routine."

Maguire said it hasn't been hard to build the muscle back up with a combination of cardio, weights and yoga.

"I'm a vegetarian," he said. "It can be a little tedious sometimes. You're eating more than you'd like to eat or you're not working out as much as you'd like. But it's fine."

The behind-the-scenes interview with Maguire and Kirsten Dunst, his on-screen love in the "Spider-Man" movies, was shown Thursday, immediately before the MTV Movie Awards.

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