Michael Weatherly has dropped a ton of weight!

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The 46-year-old actor, who showed off his transformation on Tuesday night's premiere episode of NCIS, revealed that it was a lot of work to get into tip-top shape.

"My friend and I have been swimming in the Pacific every weekend [since early May], and I lost 35 pounds!" he told Closer Weekly.

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In August, the actor even shared an Instagram photo of himself before he was heading out for a swim.

But, that wasn't the only exercise he did. Weatherly also biked and ran 22.5 miles at the Nautica Malibu Triathlon on Sept. 14. "Hopefully, I'll be able to make my family proud!" he said.

Aside from his family, Weatherly told the magazine that his NCIS co-stars also encouraged him to get in better shape. "I learned that if you say you're meeting someone at 8 a.m. on a Sunday, you have to show up," he explained.

However, Weatherly has been working on his fitness for years. "I started running around my 30th birthday," he told Details magazine in 2012. "I wanted to lose weight; I didn't anticipate the serenity. Being in motion, suddenly my body was busy and so my head could work out some issues I had swept under a carpet of wine and cheese. Good therapy, that's a good run. And I like to sweat. It's better than being cold. I like hot countries. I like endorphins. But I don't want to jump out of a plane or take karate or mixed martial arts."