NCIS star Michael Weatherly has debuted a trimmer physique after adopting a new exercise regime and dropping 35 pounds (15.9 kilograms).

The actor has been a runner for several years, but a new breakfast swimming session inspired him really shape up.

He tells Closer Weekly magazine, "I learned that if you say you're meeting someone at 8am on a Sunday, you have to show up.

"My friend and I have been swimming in the Pacific (Ocean) every weekend since early May, and I lost 35 pounds!"

Earlier this month (Sep14), the actor participated in the Nautica Malibu Triathlon and discovered he's now more a swimmer than a runner, adding, "The run killed me."