WASHINGTON – Here's another first for Michelle Obama: First among Forbes magazine's 100 most powerful women in the world.

In the annual rankings released Wednesday, Forbes says Mrs. Obama has been a "true change-maker" since coming to the White House. The business publication cited her high approval ratings, her status as a role model and her campaign against childhood obesity.

Forbes said it decided to "look up and out into the broader culture" to compile the list of women from the arenas of politics, business, media and lifestyle.

Mrs. Obama displaced German Chancellor Angela Merkel (AHN'-geh-lah MEHR'-kuhl), who had held the top spot for the last four years.

The first lady landed in 40th place on Forbes' 2009 list.