Mr. Obama has changed in many ways since winning the presidency. His hair is speckled with gray. He is more skeptical of military solutions to intractable foreign problems. His teenage daughters, he has said many times, no longer think he is cool.

But another change that has received far less attention has been Mr. Obama’s embrace of science.

He began an annual tradition of science fairs, arguing that if he celebrates the nation’s top athletes at the White House, he should do the same for the best young scientific talent. He often mentions the students he has met at the fairs, including Elana Simon, who at age 12 survived a rare form of liver cancer and before graduating high school helped discover its genetic cause.

Mr. Obama’s presidential science advisory committee has been the most active in history, starting 34 studies of subjects as varied as advanced manufacturing and cybersecurity. Scientists on the committee said they worked so hard because Mr. Obama was deeply engaged in their work.

“These are sophisticated people who don’t usually get overenthused,” said Ralph J. Cicerone, the president of the National Academy of Sciences from 2005 until this June. “But it’s happened again and again.”

Dan Pfeiffer, a former senior adviser to Mr. Obama, said that he once viewed Mr. Obama’s science advisory meetings as time that could have been better spent on more urgent priorities. “But the president really looked forward to those meetings, and he really came out of them energized,” Mr. Pfeiffer said.