WASHINGTON - Being elected president forces a man to take inventory of his life, so Barack Obama has trimmed his schedule to the bare essentials.

He's not in the White House yet, but gone are the hours he once spent reading novels, watching television, and obsessing over the daily transactions of Chicago's sports teams. He eats out only once every few weeks.

But one habit endures: Obama has gone to the gym, for about 90 minutes a day, for dozens of days in a row. He has always treated exercise less as recreation than as requirement, but his devotion has intensified in the last few months.

Between workouts during his Hawaii vacation this last week, he was photographed looking like the paradigm of a new kind of presidential fitness, one geared less toward preventing heart attacks than winning swimsuit competitions. The sun glinted off chiseled pectorals sculpted during four weightlifting sessions each week, and a body toned by regular treadmill runs and basketball games.

The more Obama's life intensifies, friends said, the more he relies on the gym - which is why he might be taking office in the best shape of his life.

The gym is where he releases stress, maintains a routine, and thinks without interruption. He sometimes wears headphones and barricades the outside world.

"He does it every day like clockwork," said Marty Nesbitt, one of Obama's closest friends from Chicago. "He doesn't think of it as something he has to do - it's his time for himself, a chance for him to reflect. It's his break."

To accommodate Obama during the 18-month presidential campaign, aides arranged workouts for him in several dozen states. The staff called gyms a few days before his arrival and persuaded them to close late or open early to oblige the candidate's schedule. Once, on July 17, Obama visited a gym three times within 16 hours. Other days - often before primary election nights - he flew in half a dozen friends to play a few hours of pickup basketball.

"That's one of the first things you learn working for him: You better make sure he gets his workout," said Jim Cauley, who managed Obama's 2004 U.S. Senate campaign. "If there isn't any time, he's not going to feel his best that day. . . . You have to make time for him to exercise, at least an hour or so."

Since the election, Obama's daily schedule has shown an intense focus. Until he went to Hawaii for the holidays, his routine in Chicago was unchanging: breakfast at home with his family before heading to his downtown transition office, where he puts in as many as 10 hours a day. At night, dinner at his Hyde Park home, and more talking to advisers and reading preparatory documents. On some days, he spent as little as five or 10 minutes outdoors.

But every morning around 7:30, he traveled by motorcade to the gym at Regents Park, a luxury apartment complex where his friend Michael Signator owns a condominium, and where he usually worked out with Reggie Love, a personal aide and a former Duke University basketball player, or with Marvin Nicholson, his travel coordinator.

The members-only gym features a sauna, a whirlpool, and a row of machines against a bay of windows overlooking Lake Michigan. Obama, 47, devotes half his workout to weightlifting and the other half to a cardiovascular rotation that includes a stationary bicycle, elliptical machine and treadmill. Between his warm-up and cool-down, he sometimes moves through a dozen exercises in an hour.

"It's something he takes seriously, and that's why he's in great shape," said Alexi Giannoulias, a friend of Obama's and a former professional basketball player.

Even Obama's closest friends said they marvel at how he has maintained his commitment. He went to Regents Park at 9 a.m. the day after his victory rally in Grant Park, on Thanksgiving Day, and hours before traveling to Washington for his first tour of the White House. On Dec. 19, Obama rushed to the gym before boarding a plane for his 12-day stay in Hawaii. He woke up the next morning on vacation, and went to a gym.

For the small group of reporters tasked with following Obama's every move, his fitness has become a running joke repeated in the stories they file. They sit at McDonald's while he exercises in Hawaii. They eat calorie-rich scones while he sweats at Regents Park. One reporter for the Christian Science Monitor, filing his report about one of the gym trips last month, noted: "While Mr. Obama worked at maintaining his lithe look, your pear-shaped pooler spent quality time at a local coffee shop."

Obama still suffers from one vice - smoking - although he has worked hard to quit since he started the presidential campaign. He's down from three or four cigarettes each day to what he terms the occasional "slip."

When Obama visited the White House in November, he toured the gym with President Bush and talked about exercise, said his wife, Michelle. Bush equipped Air Force One with a stationary bicycle, and he spends weekends biking at Camp David. He has often said that exercise has helped him cope with the pressures of the job.

Several presidents have found creative ways to stay in shape. John Quincy Adams swam in the Potomac. Theodore Roosevelt boxed. Harry S. Truman installed a horseshoe pit. Bill Clinton liked to jog and then head for breakfast at McDonald's.

Obama, who favors a post-workout snack of a protein bar and organic iced tea, wants to build a full basketball court where he can hold games on the White House grounds, and to maintain his usual routine of exercising at least six days a week.

"It's always been a priority in his daily routine," said Christopher Lu, a marathon runner who worked as Obama's legislative director in the Senate and will be his White House Cabinet secretary. "I think it's an example of how disciplined he is. It's one of the things that really keeps him balanced."