And, like a fairy godmother, Obama appeared — via video — to invite the contestants to visit the White House to show off their new selves.
Her time on the show was brief. Most of the show featured the contestants getting their makeovers and preparing for the visit. At the end of the program, while the contestants waited in what appeared to be the East Room of the White House, the first lady stepped in to greet them and the show ended with the words "To be continued."
The teasers for next week's episode showed Obama working out at the White House with the contestants. She was shown wiping her brow and joking, "Can't a first lady get a towel?"
The first lady's office directed requests for comment to NBC.
Todd Lubin, an executive producer of the show, said in a statement: "We shot an episode of 'The Biggest Loser' at the White House in season 8 and had a great experience, so we asked them if we could partner again. We share a common goal with the first lady to get people more active and healthy, so both parties felt it was a natural fit to join forces again and inspire people to get moving."
Obama has been a longtime advocate of healthy lifestyles through her "Let's Move!" initiative. "The Biggest Loser" previously filmed an episode on the White House lawn, visiting the first lady's garden and meeting with chef Sam Kass.
In the previews for next week, she was seen telling the contestants, "I'm a big fan" of the show.
And it's not the first time Obama has invited NBC cameras into the White House for a workout. In February, she and "Late Night" host Jimmy Fallon had a series of physical competitions — including a potato sack race and a tug-of-war.