Washington (CNN) Dietitians have been consulted in the White House kitchens. Steak has been swapped out for Dover sole, his favored fish. And hamburger buns have been discarded -- or at least the tops have.

President Donald Trump, who embarked upon a mission to shed 10 to 15 pounds in January , has acknowledged in private that he needs to lose weight. Prodded along by his White House physician and the knowledge he is approaching obesity, Trump agreed earlier this year to alter his diet and begin a new exercise plan. Five months into his regimen, people close to him say they've detected small changes, mostly in how he eats, that reflect a desire to follow doctor's orders.

But they haven't identified a discernible exercise routine beyond the weekend rounds of golf the President enjoys with the help of a cart. Trump himself has continued to downplay the importance of exercise, even questioning whether it presents more risk than reward.

On Wednesday, Trump will publicly tout the importance of physical fitness during an event on the White House South Lawn, accompanied by his daughter Ivanka and major sports figures such as legendary New York Yankees relief pitcher Mariano Rivera and Misty May-Treanor, a three-time Olympic gold medal winning beach volleyball player.

Their goal is to reverse the trend of declining participation in youth sports through initiatives and research that reinforces the importance of staying active. Whether Trump will hold himself up as a model remains to be seen.

When Ivanka Trump was questioned about Trump's fitness routine during a briefing call on Tuesday, a White House press aide told reporters she'd left for another meeting. And the White House did not respond to questions about the President's personal fitness plan.

In January, Dr. Ronny Jackson, the White House doctor, acknowledged to a room full of reporters that Trump didn't exercise regularly.

"Some people exercise, some people don't," Jackson said. "Some people just haven't done that as part of their routine. And I would say that's the category he falls in right now."

He described a joint effort with Ivanka Trump and first lady Melania Trump to improve the President's diet and introduce him to a workout plan, all with the goal of pulling him back from borderline obesity. At his physical exam in January, the 6-foot-3-inch Trump weighed 239 pounds, according to his doctor.

Among the steps Jackson detailed: enlisting a nutritionist to meet with White House chefs to advise on cutting calories; renovating the gym adjacent to the Lincoln Bedroom in the White House residence to Trump's specifications; and crafting an aerobic exercise schedule that "spares his joints and is healthy for him."

"He's more enthusiastic about the diet part than the exercise part, but we're going to do both," Jackson had said determinedly.

In March, Trump nominated Jackson to serve as secretary of Veterans Affairs. A month later, the nomination was withdrawn after allegations Jackson had mismanaged the White House Medical Unit. The administration said he would return to the medical unit but not as the President's physician.

How that affected the implementation of Trump's weight-loss routine isn't clear. Trump himself has told confidants that rounds of golf and smaller portions of food will help him shed the dozen or so pounds he'd hoped to lose by the start of next year but has downplayed the role exercise can play in improving his health.

Diet

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Inside the White House kitchens, chefs have been instructed to find ways to limit fat and calories in the dishes they prepare for Trump's meals, including the lunches and dinners he convenes almost daily with members of his Cabinet, lawmakers, outside advisers or visiting foreign dignitaries.

One swap repeat diners at the White House have noticed: Dover sole has replaced well-done steak, which Trump famously slathers with ketchup as his favorite meal.

Earlier this year, a registered dietitian was dispatched from the Walter Reed National Military Medical Center to consult with White House kitchen staff on reducing calories and fat in Trump's meals, according to a person familiar with the matter. Vegetables have begun appearing on his plate, though it's not clear how much of them he is eating.

Outside the White House, Trump is largely left to his own devices for meals. Visiting the Trump International Hotel for dinner, Trump has typically asked for his favorite steak. But on one recent visit he chose the Dover sole instead (it sells for $64 dollars a plate and comes laden with soy brown butter and capers).

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At Mar-a-Lago, Trump is often seen filling his own plate on the buffet line, which is full of calorie-rich options such as mashed potatoes and roast beef. At his golf clubs in Florida and outside Washington, Trump is known to eat a cheeseburger inside the clubhouse after a round.

One modification a recent lunch companion noticed: Trump's burger came with only half of the bun.

"I do that, too, sometimes," Rudy Giuliani, the President's private lawyer, told The Washington Post . "It's a good way to do it."

Nutrition experts say a realistic weight-loss plan would begin with cutting 500 calories from Trump's diet every day -- which, if sustained, could help him shed one pound per week. Although an imperfect calculation, such a modification would present an attainable goal, said Lisa Drayer, a nutritionist and author.

"You really have to start slowly. It's not realistic to just revamp your diet overnight," said Drayer, who suggested adding more fruit and cruciferous vegetables, such as broccoli or Brussels sprouts, would make the President feel full even as he consumed fewer calories. "It wouldn't take much for him to just make a few key changes, like that steak or the burger. That could be the deficit right there."

"He really needs someone to sit down with him and give him a personalized approach so that it will stick with the long term," Drayer said. "I think it's never too late to change, but your metabolism does slow down with age."

Exercise

Since Jackson revealed his diet and exercise aspirations for Trump, the President has downplayed the prospects of incorporating a new workout plan.

"See, a lot of people go to the gym and they'll work out for two hours and all," he told Reuters in late January. "Then they get their new knees when they're 55 years old and they get their new hips and they do all those things. I don't have those problems."

Instead, Trump said he could burn calories playing golf -- which he does nearly every weekend with the assistance of a cart.

"Like people get on a treadmill, I go play golf," he said.

Trump's most recent predecessors were exercise fiends, a trait Trump has not continued. President Barack Obama played basketball until his knees began troubling him, switching later to cardio work on machines in the White House residence.

President George W. Bush asked for workout equipment, including an elliptical machine and dumbbells, to be installed in a poolside cabana steps from the Oval Office, and a fold-up treadmill to be placed aboard Air Force One -- tasks carried out by Ted Vickey, who ran the White House Athletic Center for 11 years.

"(Trump) doesn't see exercise as much as a value as probably the last 5 presidents have," Vickey said, noting that President Bill Clinton took jogs through the streets of Washington and that President Dwight Eisenhower -- a golfer -- established the President's Council on Sports, Fitness & Nutrition, which is the group organizing Wednesday's event on the South Lawn.

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Described by the White House as a "field day," the gathering will feature stations focused on different sports, including soccer, track, flag football -- and the President's favored activity, golf.

"This is the President's Council of Sports, Fitness & Nutrition, so the President's definitely going to be there to make remarks and uplift this collaboration," said Holli Richmond, director of the council, who laid out a multi-pronged approach of research and initiatives meant to culminate before the 2020 Olympics.

If he were advising Trump on a fitness regime today, Vickey proposed a golf-centric program that incorporated cardiovascular exercise on an elliptical machine, strength training, and stretching -- including yoga, if Trump was game.

"You've got to find something they love doing. I would say 'Mr. President, work with me for four months and I'll drop your handicap 4 strokes," said Vickey, now a professor of kinesiology at Point Loma University in San Diego. "He's been like this for 70 years. We're not going to change him overnight."

"Unfortunately," Vickey said, "you have to trick him into exercise."