"I mean, there's so much more to do here in the present ...," Obama told "Good Morning America" Robin Roberts in an exclusive interview that aired on the show today. "I focus on what's before me, right on the work that I can do today."
"Whenever it's time to campaign and they tap me on the shoulder, I'll be right there. But until then, we've got some great initiatives...," she said. "And I'm rolling up my sleeves to get that work done, and we'll cross that other bridge when we get there."
Roberts' interview with Obama took place at Fort Jackson, the U.S. Army training post outside Columbia, S.C. The first lady visited the base on Thursday to get a first-hand look at how the Army is tackling the problem of obesity among service members.
Last February, she launched "Let's Move!," a campaign that seeks to end childhood obesity within a generation. Obesity is of particular concern for the military, she said, pointing out that some top Army officials have said young recruits are unable to train because they are either overweight or malnourished.
"It is not an overstatement to say that childhood obesity and our need for physical education and nutrition education is a national security issue," she told Roberts in a wide-ranging interview that also touched on the Tucson shootings, support for military families, the government's role in people's personal nutritional choices, and criticism of her fashion choices.
The first lady said the nation had made strides in nutrition legislation and public education, adding that the second year of the "Let's Move!" initiative would bring enhanced efforts to make more public schools healthier, as well as outreach to faith-based and community organizations.
The point is to "make nutrition fun again," she said.
The reliance upon heavily processed food, fast food and sweetened drinks is taking its toll. Add to that changes in society -- where increased computer usage and more TV time mean children aren't getting outside to play as much as they used to -- and the situation grows more serious.
"If we can make our society healthier, if we can make this next generation of kids healthier, we can teach them how to eat, if we can get them moving just a little bit...," she said. "If we can get the military to use its resources to change the way it feeds our troops, then we'll see progress."
Better nutritional habits that last over a lifetime will mean "billions of dollars" in savings to the nation, she noted.
Asked about critics who've said the government has no role in people's nutritional choices, the first lady said the "Let's Move!" program "has never been about the government telling people what to do. But what it is about is giving parents information -- and clear information -- so that they can make good choices."
The first lady also spoke about increased support for military families in their daily lives. Earlier this week, President Barack Obama announced the new set of initiatives that will emphasize military children's education, military spouses' educations and careers, increased child care and quality of life improvement.