updated 05/02/2011 AT 1:45 PM ET
•originally published 05/02/2011 AT 11:55 AM ET
Jordin Sparks isn’t shy.
The singer, 21, showed off her trim physique in a playful bikini photo on Twitter on Sunday.
Of her weight loss, the season 6 American Idol winner tells PEOPLE: “It was just a shift in my thinking. Instead of talking about being more active, I just got up and did it.”
“There’s no secret,” she adds. “Anybody can do it.”
Describing her polka dot orange and blue two-piece, she posted online, “I don’t know why but my bathing suit reminds me of fruity pebbles.”