Peter Jackson has gone from a giant gorilla to a hunky monkey.

The "King Kong" director shed nearly 80 pounds while shooting the monster movie remake by eating a strict diet of yogurt and muesli, getting little sleep and working around the clock, sometimes putting in 21-hour days.

It's already been dubbed the "Skull Island Diet" by the diet Web site obesitycures.com, named after the tortuous jungle where King Kong was born.

"I just got tired of being overweight and unfit, so I changed my diet from hamburgers to yogurt and muesli and it seems to work," Jackson told Britain's Daily Telegraph newspaper.

The New Zealand director, 44, barely got any rest since completing the "Lord of the Rings" trilogy, jumping into "King Kong."

"I'm exhausted and just absolutely tired," he told moviehole.net. "I felt fit for a while but then the film has been such a grueling marathon to do. I haven't enjoyed being healthy yet, I am absolutely shattered and I haven't really had a life. I've been making movies for about 10 years solid now."

In town for the Kong premiere on Monday night, Jackson looked refreshed and youthful on the red carpet, posing for pictures alongside stick-thin actors Naomi Watts and Adrien Brody.

Gone are the nerdy glasses -- he had laser-vision correction -- sloppy shorts and scrubby polo T-shirts. Jackson's double chin was replaced by a toothy grin. His eyes were sparkling and he was wearing a sleek black blazer with a striped button-down shirt.

"It's new and I love it," says Tom Cardy, arts editor at The Dominion Post in New Zealand, who has been writing about Jackson since 1998.

"He looks a lot healthier and he had more color in his skin."

Cardy says Jackson has been shedding pounds since pre-production on "King Kong" began, which started immediately after he won an Oscar for "Lord of the Rings: Return of the King" in February 2004.

Six months later, in August 2004, Jackson held a "King Kong" press conference in New Zealand, and revealed his new physique.

"It [his weight loss] has been a topic of conversation over the time," says Cardy. "People have brought it up."

Off the red carpet, Cardy claims that Jackson has looked tired and weak.

"I saw him last October, and I'd never seen him look so visibly tired before," he said. "He looked completely shattered. I've never seen him look so exhausted. Maybe the weight loss exacerbated it."

If more work means extra weight loss for Jackson, then he's got a lot more slimming in line. The beloved director will be directing "The Lovely Bones" and is an executive producer on "Halo," both slated for release in 2007.