"[Philanthropy] is what I'm all about," the U.S. Naval Officer, triathlete and physician, 31, tells PEOPLE. "I don't have that much money to begin with, but to use the fame to give back, and promote things that you're passionate about, that's the way I'm living my life right now."
When he's not mentoring medical students, giving motivtional speeches or fighting for pancreatic-cancer awareness, Baldwin likes to work up a sweat. On Sept. 14, he came in first in his division – bettering Matthew McConaughey! – in the Nautica Malibu Triathlon.
"It was a fun time – I defended my title!" he says, adding that his heavy work schedule makes training difficult.
As for his fellow celeb competitors, "It was nice to meet [McConaughey]," he said. "We were chatting out in the waves before the start ... and then we got up on the podium and he looked up at me and he was like, in his typical accent, you know, he's like, 'Man! You didn't tell me you were that fast! You gotta give me some tips.' "
And J.Lo? "She was sweet," he says. "I was giving her some pointers on [swimming] and helping her relax."
On the Dating FrontNo longer dating Marla Maples ("I'm proud to call her a friend"), Baldwin says that he's looking for a girl who gives back – and isn't afraid to get a little sweaty. … I think it's sexy to be with somebody after you worked out."
Ideally, he says, he seeks someone who is "very giving and [into] helping others."