First lady Michelle Obama knows she has star power, and she has used it for four years to champion her causes of fighting childhood obesity and helping military families.

But now that she has successfully made it through the last political campaign for her husband, President Barack Obama, the first lady is also having fun with her popularity - raising questions over whether she has gone too far in becoming a pop culture icon.

Her surprise appearance at the Academy Awards - where she was beamed in from the White House dressed in a sparkling evening gown to announce the Best Picture award - provided ammunition for her critics.

The first lady has enjoyed a steady positive approval rating over the past four years, even at times when her husband sank in the polls.

But the Oscar appearance - coming on the heels of the "mom dance" that she did with late night comedian Jimmy Fallon, which quickly went viral on the Internet - sparked a debate on the proper role of a first lady.

Washington Post columnist Courtland Milloy, who often writes about minority issues, described Obama's Oscar appearance as "unbecoming frivolity" and urged the first lady to "raise her game" and take up a more expanded role in the second term championing more serious causes.

"Enough with the broccoli and Brussels sprouts," Milloy wrote this week in the Washington Post. "Where is that intellectually gifted Princeton graduate, the Harvard-educated lawyer and mentor to the man who would become the first African American president of the United States?"

His column sparked hundreds of comments, ranging from people who thought Obama was doing a great job raising awareness about the childhood obesity problem to others who thought she was trying too hard to be like a Hollywood star.

The first lady said she was not surprised by the controversy over her Oscars appearance, but said she would use all forms of media to get out her message and would reach out to all demographics - including filmmakers who could help with her efforts to introduce children to arts and culture.

"Anyone in this position has a huge spotlight," Obama told a small group of reporters traveling with her on a three-city tour to promote her Let's Move program to fight childhood obesity.

"We've always thought about that spotlight. And taking it, while it's looking at you, to stand in front of something good so it shines on that too," Obama said, before jumping and dancing with more than 6,500 kids gathered in Chicago to highlight the importance of daily exercise.

(Read by Brian Salter. Brian Salter is a journalist at the China Daily Website.)

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