"The main reason I do it is just to clear my head and relieve me of stress," Obama told Men's Health magazine. "My blood pressure is pretty low and I tend to be a healthy eater."
"Most of my workouts have to come before my day starts," he said. "There's always a trade-off between sleep and working out. Usually I get in about 45 minutes, six days a week. I'll lift [weights] one day, do cardio the next. I wish I was getting a 90-minute workout."
But some days look obsessive. During the primaries, ABC News reported that Obama worked out 188 minutes in gyms on one day. First, he used his friend's Chicago gym, then he campaigned in Indiana before returning for another workout. After that, he played basketball.
The campaign said his initial gym visit was interrupted by a telephone call, so he went back to finish. Obama also met with his trainer at Chicago's East Bank Club to check on a sore hip.
Obama's passion is basketball, which he often plays at the East Bank Club with his old friend Arne Duncan, CEO of the Chicago Public Schools, and his brother-in-law Craig Robinson, basketball coach at Oregon State University.
"What the public doesn't see is how competitive he is," Duncan told ABCNews.com. "He plays to win."
"He's an athlete," he said. "This is an important part of who he is."
Duncan said he and other players don't hold back for fear of hurting the president-elect.
"We don't take it easy," he said. "That would ruin the competitive nature of the games, and that's what it's all about."
Obama told ABC News' Barbara Walters that he considered tearing up the White House bowling alley and replacing it with a basketball court.
"Well, it turns out that there's a tennis court in the White House, and I think the guys in charge say they maybe can put a couple of basketball hoops at either end. So that may be good enough for spring," he said. "And, I hear there's a gym at Camp David. So, we may leave the bowling alley in place, partly because it's clear I'm going to have to practice if I want to get any good."
The half-joke about his bowling abilities referred to a campaign stop in a bowling alley where he quit trying after throwing nothing but gutter balls.
Obama's predecessor was no slouch when it came to fitness: Bush was known to jog on a treadmill aboard Air Force One, cycle, weight lift and stretch six days a week.
On Election Day, Obama played what had become his "lucky charm" basketball game with old high school and law school friends. Duncan and Casey joined them.
"He did really well," Casey told ABCNews.com. "He's actually a very good player."
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