AceShowbiz - More than a year after she suffered a near-fatal heroin overdose, Demi Lovato is gearing up for her music comeback. The 27-year-old singer/actress is reportedly preparing to return to the spotlight and perform again, but first she wants to get in tip-top shape.

The "Camp Rock" star is allegedly concerned about her weight and has been hitting the gym harder than before to lose weight. "Demi wants to get down to her fighting weight," a source tells Fame (via Radar Online).

"And she's doing all she can to get there and be ready to be seen performing again," the source goes on sharing, adding that the "Give Your Heart a Break" hitmaker has doubled up on her Jiu Jitsu workouts and high-intensive interval training to achieve her goal.

Demi was rushed to the Cedars-Sinai Medical Center in Los Angeles after emergency services were called to her home due to an opioid overdose in July. The accidental overdose came just a month after she released "Sober" in which she revealed she had relapsed after six years of sobriety.

She was hospitalized for two weeks and subsequently entered an in-patient rehab facility. After completing her rehab, she has been keeping a low profile. She recently signed with Scooter Braun, who also manages Justin Bieber and Ariana Grande among other artists.

The "Sorry Not Sorry" star, who turned 27 on Tuesday, August 20, celebrated her birthday with her new manager Scooter and label mate Ariana at the latter's concert at O2 Arena in London. In a black-and-white video she posted on Instagram, the former child actress blew some candles on a birthday cake presented to her backstage.

She also revealed that "they literally filmed/sang happy birthday twice" but Scooter forgot to press the record button both times. She still looked happy though as she flashed a big smile while her friends were clapping their hands.