When Britney Spears guest starred in an episode of “How I Met Your Mother,” people were talking about how good she looked. It appeared that she was becoming more healthy and had lost some weight.

“It looked like Britney had lost 15 pounds in four weeks,” a source close to the singer tells OK!.

“Britney’s a pro at losing weight fast,” a Spears pal tells OK!. “She can drop seven to 10 pounds in two weeks.”

Sources say “Brit has given up her old unhealthy weight loss habits, like popping laxatives and diet pills.”

“To complement her healthier eating habits, Britney works out regularly as well, although you probably won’t see her jogging around her neighborhood. The recovering pop star enjoys daily dance workouts at L.A.’s Millennium Dance Complex, where sources tell OK! she does squats along with chair and pole dancing.”