Obama - who is 15 years younger than Trump - assumed office at the age of 47, and the results from his 2016 physical painted a healthy picture. However, he said, Trump was aware of the public discussion of his mental state and asked Jackson to give him one anyway.
The Navy doctor exhausted reporters' questions during an unusually lengthy hour-long session, at Trump's request, and said he did not withhold any information in the interests of privacy. Here's how the two presidents' health stack up.
To check for possible cognitive dysfunction, the US Department of Veterans Affairs uses the Montreal Cognitive Assessment (MoCA) neuropsychological test. Jackson said he would increase that dose in an effort to get Trump's so-called "bad" cholesterol, or LDL level, below 120; it now is 143.
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.
"Anything above 26 is normal, and certainly if you get a 30 out of 30, I think you can confidently assume that you're done on the cognitive workup for now", said Rear Adm. Dr. Ronny Jackson, who on Friday spent three hours examining Trump with a team of doctors at Walter Reed National Military Medical Center in suburban Maryland.
Jackson said the president requested he be given a cognitive test - something the doctor said he normally does not do in these types of exams but obliged on because of Trump's insistence.
Despite the diet and cholesterol concerns, Dr Jackson stressed that Mr Trump's 'cardiac health is excellent'.
Jackson describes Trump as "very sharp" and "very articulate when he speaks to me".
Even without Alec Baldwin's President Trump, "Saturday Night Live" still found a way to mock the commander in chief.
Trump asked that a cognitive test be included as part of his first physical exam, Jackson said. It is "just one measure in a clinical judgment", he said in an email.
"Trump is 6'3" and weighs 239 pounds.
Dr Jackson said he prescribed a diet lower in fat and carbohydrates, and exercise.
"Like most men of his age, President Donald Trump has a common form of heart disease, relatively easy to address if he increases the dose of his cholesterol-lowering medication and makes necessary lifestyle changes", he wrote.
"He's more enthusiastic about the diet part than the exercise part", he joked.
The White House physician said several times that there was nothing he was holding back, and that neither Trump nor his aides had coached him on what to say.
Townhall political editor Guy Benson said, "The respected doctor who actually examined Trump says otherwise".