Original "The Voice" coach Christina Aguilera has lost 15 pounds after giving birth on Aug. 16 to her daughter, Summer Rain, by her 29-year-old fiancé Matthew Rutler.

"She's losing weight at a rapid pace and will have lost all of the 35 pounds she gained during pregnancy within a matter of weeks," a source told Radar Online indicating that the 33-year-old "Beautiful" singer is not done losing weight yet.

The source added Aguilera looks incredible as she is "doing a lot of yoga, meditation, treadmill, boxing and working out with her personal trainer" while breastfeeding, which "takes away all of that bloat."

While she is consuming only about 1,600 calories a day, the mother of two is required to have an extra 500 calories to breastfeed, the source explained. Aguilera also has a six-year-old son, Max, by her former husband, Jordan Bratman.

Apparently, Aguilera is preparing for her return as a coach to "The Voice Season 8" after her maternity leave.

On Oct. 14, Tuesday morning, host Carson Daly announced on the "Today" show No Doubt singer Gwen Stefani will no longer fill in for Aguilera again for the next season of "The Voice," which will premiere early 2015.

"The Voice Season 7" features not only Stefani as the second female coach to fill in for Aguilera after Shakira but also Taylor Swift as a guest mentor.

As confirmed by NBC, the line-up of coaches for its top-rating reality series "The Voice" for its eighth season includes original coaches Aguilera, Blake Shelton and Adam Levine with Pharrell Williams returning for another season filling for original coach CeeLo Green, Deadline has learned.

The return of the "Happy" hit maker, "The Voice Season 8" is the first season of the show that stopped the rotation of coaches every other season, according to New York Daily News.

NBC Entertainment Alternative and Late Night Programming president Paul Telegdy said, "We are excited to welcome Christina back to her red chair and can't wait to see how she mixes things up among Adam, Blake and Pharrell, in what will be an incredibly competitive competition."