Jackson said that though not required by the exam protocol or recommended, he conducted a cognitive test on the president at his insistence in the light of questions raised by critics.
He also said he found the president, whom he about three times every day, always "very sharp" and "very articulate".
Trump's flying colors on his cognitive test gave his supporters ammo to try to put to rest the narrative that has emerged in recent months that Trump is mentally unfit for office or could even be experiencing early stages of dementia or Alzheimer's disease.
In the book, sources close to the president and the administration had said that Trump was prone to repetition and that aides regularly questioned his mental stability. Trump has said that he has never smoked or imbibed alcohol, which Jackson said has contributed to the president's good health.
Rear Adm. Ronny Jackson, the White House physician, speaks about President Trump's health at a White House news briefing on Tuesday. "The answer to your question is that he has incredibly good genes, and it's just the way God made him". Jackson said there is "absolutely nothing" that is being withheld from the public and that Trump's release of information is "hands down" the broadest in history. There were 12 additional consultants in the room.More news: Root helps England take 2-0 series lead over Aussies
Trump took the test during the annual physical that is customary for presidents at the Walter Reed National Military Medical Center in Maryland on Friday.
A White House official told the Washington Examiner that it had nothing to add to Dr. Jackson's statements.
The President intends to take diet and exercise steps to lose perhaps 10 to 15 pounds, and is also planning to take a higher dose of Crestor, a cholesterol medication, Jackson said.
New York Magazine wrote that while it's possible Trump's numbers were fudged, "it's more likely that Trump actually weighs 239 pounds, and comparing him to the 239-pound bodies of professional athletes is just skewing perceptions". The only medications he is now taking are Propecia for male hair loss, one for Rosacea and a multivitamin, Jackson also confirmed. Jackson said he hopes to bring down the LDL or "bad cholesterol" score with diet, exercise and statin medication. "It took significantly longer to complete, but the President did exceedingly well on it".
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.