Trump to get physical amid questions on health, fitness

During the campaign, Donald Trump's longtime personal physician asserted that the Republican candidate would be "the healthiest individual ever elected to the presidency."

Now, a year into his presidency, the 71-year-old Trump -- the oldest person ever to assume the job -- is set to undergo his first checkup as commander in chief. Trump heads to Walter Reed National Military Medical Center on Friday for a presidential physical, according to the White House.

It's expected that Trump will undergo a battery of tests to assess his health across a broad range of categories and be physically examined by a team of specialist doctors overseen by presidential physician Dr. Ronny Jackson.

Jackson, a rear admiral, has served as a White House physician for the past three administrations, according to the Navy. He was the primary physician for President Barack Obama and currently serves as the physician to the president for Trump.

Trump's checkup comes amid recent questions about his health and publication of the new book, "Fire and Fury: Inside the Trump White House," which casts doubt on Trump's fitness for office. It's also drawing close attention given the limited amount of information previously made public about Trump's health and medical history.

Press secretary Sarah Sanders has said the White House will provide a "readout" of the exam after it's completed. But it's not clear whether Trump will adhere to the level of detail released by his most recent predecessors.

What is a presidential physical

At least as far back as President Richard Nixon, it has been standard practice - though not a formal requirement - for the commander in chief to undergo periodic physicals with the express purpose of providing the public with the assurance that the nation's leader is "fit for duty."

Following the exam, the president's physician has typically summarized and made public a wide range of results, including basic vital information on the president's physical condition such as weight, body mass index, heart rate, cholesterol levels, blood pressure, medications and social habits.

There is also typically a comprehensive list of results from the various physical tests run. President Obama's 2016 physical summary noted the following: eye exam, ears, nose and throat, thyroid exam, lungs, heart, skin, genitourinary, gastrointestinal, musculoskeletal and neurological.

A neurological exam evaluates a person's nervous system, which includes the brain, spinal cord, and related nerves, according to the Johns Hopkins Medicine Health Library. It's unclear whether Trump will receive such an exam; he is not expected to undergo a formal mental health assessment, officials said.

A summary of President George W. Bush's first physical, conducted in 2001, concluded that Bush was "in excellent health and 'fit for duty'." Bush continued a practice, as many presidents had before him, of receiving an annual physical over the course of his presidency.

President Obama had fewer physicals than Bush did, undergoing a total of four periodic examinations over eight years. In a summary following Obama's final checkup in 2016, presidential physician Jackson stated that "the purpose of this exam was to provide the public with an update of the President's current health status." Jackson concluded that the president was in "excellent" health, with all indications that he would remain so "for the duration of his Presidency."

What the physical likely won't cover

During the campaign, the public had limited information with which to assess then-candidate Trump's physical fitness, even as he regularly raised questions about his opponent's physical stamina and ability to serve in the Oval Office.

The most detailed information ever released about Trump's physical condition came just two months before he was elected in 2016 and was revealed during an appearance on the Dr. Oz show.

On the September 2016 program, then-candidate Trump handed Dr. Oz a letter from his longtime personal physician Dr. Harold Bornstein, which detailed some basic vital information - including that he is 6 feet 3 inches tall and his weight is 236 pounds. The letter also listed his cholesterol levels and blood pressure, stated that the results of his cardiac evaluation were normal, that his last colonoscopy in 2013 was also normal, listed his testosterone level at 441.6, and stated that he takes a cholesterol medication and low dose aspirin.

Bornstein declined to comment for this report when reached by ABC News.

The letter also stated that Trump has no family history of premature cardiac or neoplastic disease and noted that his parents, Mary and Fred, lived into their late 80s and 90s. But it omitted that Trump's father battled Alzheimer's Disease in the final years of his life.

That information supplemented the famous four-paragraph-long letter from 2015 in which Trump's longtime physician asserted that Trump would be "the healthiest individual ever elected to the presidency." The letter also said that Trump had recently undergone a "complete medical examination that showed only positive results. Actually, his blood pressure, 110/65, and laboratory results were astonishingly excellent."

After revealing more comprehensive results to Dr. Oz in 2016, Trump admitted that he could benefit from losing some weight after Oz noted that the president's weight-to-height ratio showed him to be overweight.

"I think I could lose a little weight," Trump told Oz. "If I had one thing I'd like to lose weight, but it's tough, it's tough because of the way I live."

As for the president's lifestyle and daily health habits, he has said he has an affinity for fast food but does not drink alcohol or use tobacco. Two of the president's former campaign aides, Corey Lewandowski and David Bossie, even wrote about Trump's love for McDonald's in a book.

"Trump's appetite seems to know no bounds when it comes to McDonald's, with a dinner order consisting of two Big Macs, two Filet-O-Fish, and a chocolate malt," they wrote in their book, "Let Trump Be Trump."

The president's daughter and current White House adviser, Ivanka Trump, has publicly expressed concern about her father's eating habits.

"I want him to eat healthier," Trump told ABC News' Barbara Walters in a November 2015 interview.

Beyond his diet, the president does not lead an especially active lifestyle. Outside of golf, the president is not known to regularly exercise, and has reportedly described exercise as a "misguided" concept, "arguing that a person, like a battery, is born with a finite amount of energy," according to a New Yorker article by Evan Osnos.

Questions about the president's physical condition have recently become part of the public discourse after an incident on Dec. 6 when the president appeared to have difficulty pronouncing some words and seemed to slur others during remarks broadcast on national television.

After initially declining to comment, the White House dismissed the president's speech issues as nothing more than a case of dry mouth.

"I know that there were a lot of questions on that - frankly, pretty ridiculous questions," press secretary Sanders told reporters the following day. "The President's throat was dry. Nothing more than that."

What the physical likely won't cover

But for all the upcoming examination might reveal about the president's physical condition, it is not expected to offer any sort of assessment of the president's mental fitness at a time when some members of Congress and mental health professionals have raised questions about the president's stability.

The president, for his part, has asserted that he is a "very stable genius."

After the publication of the new book "Fire and Fury" claimed that members of the president's inner circle regularly question Trump's mental fitness, the president fought back on Twitter, saying that "mental stability and being, like, really smart" are two of his greatest assets.

Outgoing Republican Sen. Bob Corker, R-Tenn., has been one of the most outspoken members of the president's party in expressing doubts.

"The president has not yet been able to demonstrate the stability nor some of the competence that he needs to demonstrate that he needs to be successful," Corker told reporters in August.

Trump is not alone in presidential history in facing questions about his fitness; questions were raised about Ronald Reagan's fitness in the final years of his presidency. It wasn't until six years after Reagan left office, though, that he was diagnosed with Alzheimer's Disease.

Following Richard Nixon's annual physical in 1974, at a time when there were reports that the stresses of the Watergate scandal were affecting his health, the president's physician Walter Tkach declared after the check-up that there were no signs of "emotional strain" on the commander in chief.

"There is no evidence of any emotional strain. I do not see any physical evidence of any strain," White House physician Walter Tkach told reporters, according to a Washington Post article from the time.