Former President Barack Obama checked in with Hillary Clinton during last year's campaign to see if she was sleeping and eating properly, Clinton said Monday night.

"He was an extraordinarily supportive and helpful friend throughout the whole campaign," Clinton said at the Warner Theatre in Washington, D.C. "He would call me periodically and he would say, ‘Are you getting enough sleep? Are you, you know, eating well?' I'd say ‘Oh, I think I'm getting enough sleep. I think I'm eating well.'"

"Then he'd say ‘Well are you exercising?' I'd say ‘I think I'm getting enough sleep and I think I'm eating well,'" she said.

"He really, you know, stayed up with me," Clinton said. "Stayed up with the campaign. And I can't remember which of the incidents he might have been referring to, but he was always just in my corner and had my back throughout the whole, you know, 18 months or nearly two years."

Clinton said Obama also warned her against trying to be "hip" during the campaign, something she wrote about in her book, What Happened.

"So there is a very funny moment in the book when you say that president Obama told you, ‘Don't try to be hip. You're a grandma. Just be yourself,'" Lissa Muscatine, co-founder of Politics & Prose Bookstore, said Monday during her interview in Washington. "My question, did he think you were going to run off to a Soul Cycle class or take a mixology course, or chia pudding? What was he worried about?"

"There are probably so many examples," Clinton responded.