Obama also spoke about her father, who died in 1991, and his painful battle with MS in her speech to the Democratic National Convention this month.

Her fears of MS provide an interesting comparison to the woman married to the man challenging President Obama’s reelection. Ann Romney was diagnosed with MS in 1998, and has frequently spoken of it in interviews and on the campaign trail. The disease is now in remission. The causes of MS are still unknown.

The current first lady is known for her healthy lifestyle advocacy and Let’s Move, her anti-childhood obesity initiative. She showed Dr. Oz some of her moves, including teaching him the Dougie and the proper way to jump rope.

But she said she never chides the president for all the ice cream, beer and pizza stops, much less the State Fair tours, that he makes during local visits on the campaign trail. 

“Truly, in our household it’s about moderation,” she said, calling the president “one of the healthiest people I know.”

“When he goes out on the campaign trail and somebody offers him ice cream, you don’t say no,” she said. “We learned that growing up. If somebody offers you a fried Twinkie, you take a bite. You don’t diss somebody else’s stuff.”