The first lady went to Watertown, Wis., to take part in a Partnership for a Healthier America campaign intended to get people to drink more water.
"I've come to realize that if we were going to take just one step to make ourselves and our families healthier, probably the single best thing we could do is to simply drink more water," she said. "That's it -- it's really that simple. Drink just one more glass of water a day and you can make a real difference for your health, your energy, and the way you feel."
Sam Kass -- White House assistant chef and director of the first lady's Let's Move campaign on behalf of physical fitness -- said health problems including obesity can be alleviated by drinking more water.
However, Dr. Stanley Goldfarb of the University of Pennsylvania, a kidney specialist, told Politico scientific data do not support the more-water recommendation.
"I think, unfortunately, frankly, they're not basing this on really hard science," he said. "It's not a very scientific approach they've taken. ... To make it a major public health effort, I think I would say it's bizarre."
"We're designed to drink when we're thirsty," Goldfarb said.
University of North Carolina professor of nutrition Barry Popkin said water "is the best thing we could drink" but the Drink Up campaign is not justified by "our science of water and dehydration."