Trump, 71, is known to enjoy high-fat foods like fried chicken, hamburgers and steak - and, while he plays golf, he does not have a daily exercise routine.
Jackson said Trump is going to try to lose 10 to 15 pounds (4.5 to 6.8 kg) by eating better and starting to exercise,
The Navy doctor exhausted reporters' questions during an unusually lengthy hour-long session, atTrump's request, and said he did not withhold any information in the interests of privacy.
"He said, 'I want you to get out there and I want you to talk to them and I want you to answer every single question they have,'" Jackson said of Trump.
Trump's mental fitness for the job had come under intense scrutiny after a recently published, controversial book, "Fire and Fury: Inside the Trump White House," portrayed him as childlike and mercurial.
Past presidents are not known to have been tested for mental acuity while in office - including Ronald Reagan, who five years after leaving the White House in 1989 was diagnosed with Alzheimer's disease, an incurable, degenerative brain condition.
Jackson, who speaks with Trump a few times a day and travels with him, said he did not think the president needed cognitive testing based on medical guidelines - but added the 30-question Montreal Cognitive Assessment at Trump's request.
The test looks for signs of Alzheimer's or other forms of dementia. Sample questions include asking the patient to draw a clockface, putting in all of the numbers and setting the clock hands to a specific time. The test does not assess psychiatric fitness.
Trump scored 30 out of 30 on the test, Jackson said. "The president is mentally very sharp, very intact," the doctor said.
Dr. Ronald Petersen, an Alzheimer’s expert at the prestigious Mayo Clinic, said he could not comment specifically on the president's cognitive health. However, he did say that, in theory, a perfect score on the Montreal test does not necessarily rule out cognitive decline. It is "just one measure in a clinical judgment," he said in an email.
MORE ENTHUSED ABOUT DIET THAN EXERCISE
Trump is considered overweight and borderline obese at 6 feet 3 inches (1.9 meters) tall and 239 pounds (108 kg). His blood pressure was 122/74, within normal bounds, and his cholesterol was on the high side, Jackson said.
But the physician said Trump's cardiac health was excellent, noting the president had undergone an exercise stress test, and said he consulted cardiologists about Trump's coronary calcium score.
Jackson credited the results to genetics. "It's just the way God made him," he told reporters.
Jackson said he would increase Trump's daily dose of Crestor, a cholesterol-lowering drug, and bring in a nutritionist to work with White House chefs. The doctor said he would also design a daily exercise program for Trump.
"He's more enthusiastic about the diet part than the exercise part, but we're going to do both," Jackson said, adding that he might enlist first lady Melania Trump to help.
Ranit Mishori, an attending physician at Georgetown University-Providence Hospital in Washington, said Trump received more screening and diagnostic tests than are generally recommended for someone at his age and with his medical history.
With his reported eating habits and lack of exercise, it made sense for the White House to "release all of this data to show that ... he is in good health," Mishori said.
Even without red flags from test results, Mishori said it was clear that Trump faces some risks.
"He is a male and he is in his 70s and he is overweight, borderline obese, and he has high cholesterol. Those four factors alone put him at a higher risk for cardiovascular disease," she said.
Mishori disagreed with Jackson's assessment that Trump would be healthy for the rest of his term and possibly a second four-year term.
"This was a bit of a snapshot in time," she said. "I don't think this can be a definitive sign that he will be in this same state of health for the remainder of his term."
(Reporting by Ayesha Rascoe and Roberta Rampton; additional reporting by Julie Steenhuysen in Chicago and Makini Brice in Washington; Editing by Bill Trott and Jonathan Oatis)
© Reuters News 2018