WASHINGTON — President Biden’s personal physician said on Friday that he was a “healthy, vigorous, 78 year old” who was fit to carry out his duties, after the president underwent a full medical evaluation and briefly transferred powers to the vice president so he could undergo a colonoscopy.

Dr. Kevin O’Connor, the president’s physician, said that Mr. Biden had developed a “more pronounced” tendency to cough and clear his throat during speaking engagements. After running tests, including those meant to detect 19 various respiratory pathogens, Dr. O’Connor said the culprit was gastroesophageal reflux, or acid reflux, a condition treatable with Pepcid.

Dr. O’Connor also said that Mr. Biden’s gait had become stiffer, which he said had been caused by age-related changes in the president’s spine. He added that an “extremely detailed neurologic exam” had ruled out the possibility that the stiffness could be caused by a stroke, multiple sclerosis, Parkinson’s, or other neurological disorders.

A foot fracture Mr. Biden suffered last year “has healed nicely,” Dr. O’Connor said, though he added that the president could benefit from orthopedic shoes.

A three-millimeter “benign-looking” polyp was found during what Dr. O’Connor said was a regularly scheduled colonoscopy, and a pathologist’s evaluation of the polyp is expected to be completed next week. Mr. Biden’s lipid levels are “remarkably low,” Dr. O’Connor said.

During the colonoscopy, Vice President Kamala Harris became the first woman to assume acting presidential duties. She spent that 85-minute span of time in her West Wing office watching live television coverage of the House passing a large social spending package, her office said.

Historically, presidential checkups are used to bolster whatever image the president wishes to present about his health, and the details provided relate in no small part to the president’s age and health. There is no template for what presidents should release about their health, and the details they choose to disclose are up to them. In Mr. Biden’s case, his physical was not included on his public schedule ahead of time, and was performed amid an onslaught from conservative commentators raising questions about his age — he turns 79 on Saturday — and his fitness to hold office.

Polling released by Politico and Morning Consult this week found that a growing number of voters do not think that Mr. Biden is in good health, and that voters are about evenly split on whether he is mentally fit.

Mr. Biden’s predecessor, Donald J. Trump, faced similar questions about his mental acuity throughout his presidency. In 2018, questions about his mental health, fueled by the publication of the book “Fire & Fury,” intensified to the point that Mr. Trump insisted to the public that he was a “stable genius.”

Dr. O’Connor did not say in his report whether Mr. Biden underwent cognitive testing, which many doctors recommend for older adults. Dr. O’Connor served as Mr. Biden’s physician when he was vice president, and was named the president’s physician on Inauguration Day.

Since Mr. Biden assumed office, Republicans have made repeated references to his age. In September, Senator Jim Risch, Republican of Idaho, quizzed Secretary of State Antony J. Blinken in a Senate hearing about Mr. Biden’s fitness for office, declaring the Biden presidency a “a puppeteer act.” In that exchange, a bemused-looking Mr. Blinken replied that “the president very much speaks for himself.”

In presidential physicals, the White House often provides specific information on height, weight and cholesterol. President George W. Bush’s physicals noted that he smoked the occasional cigar. His decision in 2002 to undergo a colonoscopy at Camp David — and briefly transfer presidential power to Vice President Dick Cheney — made headlines.

Dr. O’Connor said Mr. Biden’s physical exam was “fundamentally unchanged from baseline” aside from new findings that concluded he had mild peripheral neuropathy, a condition defined by nerve damage, pain and stiffening in the feet. Despite extensive testing, the team found no cause for that condition.

Mr. Biden’s height, 5 feet 11 inches, and weight, 184 pounds, earned him a body mass index of 25, which is on the low end of overweight.

Presidential physicals are “only as credible as the doctor delivering them, is what we’ve learned,” said Matthew Dallek, a political historian. “Biden appears to be much more straightforward than a lot of presidents and more transparent in the 10 months or so he’s been on the job, but because we don’t have access to all of the details, it’s very hard to rely completely on these reports.”

Mr. Biden’s physical and colonoscopy took place at the Walter Reed National Military Medical Center in Bethesda, Md.

The White House released the specialties of the medical professionals who evaluated Mr. Biden, as a number of his predecessors have. Mr. Biden was treated by consultants who specialize in optometry, allergy treatment, dentistry, foot and ankle orthopedics, spine orthopedics, physical therapy, neurology, cardiology, radiology, dermatology, anesthesiology and gastroenterology, Dr. O’Conner said.

A geriatrician was not among the medical specialists from 12 disciplines who participated in the president’s detailed health checkup on Friday. Geriatrics is the specialty that focuses on the elderly. Consultations with geriatricians are usually determined by a patient, or his or her primary care physician. There is no specific age at which geriatricians typically begin examining patients.

Mr. Biden used Section 3 of the 25th Amendment to temporarily transfer power during his colonoscopy. Under that provision, the president was required to notify the president pro tempore of the Senate, Patrick J. Leahy, Democrat of Vermont, and Speaker Nancy Pelosi that he was temporarily unable to carry out his presidential duties. Those letters were transmitted to both at 10:10 a.m.

Mr. Biden resumed his duties around 11:35 a.m. on Friday, Jen Psaki, the White House press secretary, said on Twitter, adding that he was “in good spirits.” Three hours later, the president emerged from Walter Reed and told reporters that the procedure had gone well.

“Good! We’re gonna release all the details. I feel great. Nothing’s changed. We’re in great shape,” Mr. Biden said, before returning to the White House to pardon a pair of turkeys. “And I’m looking forward to celebrating my 58th birthday.”