The former Spice Girls singer, who mentored Tyla Bertolli before she was eliminated from the reality television show earlier this week, told her that she needed to regain some of the 12kg she lost before entering the competition.
Bertolli told the Herald Sun that Mel B ordered her to "eat a burger", warning her that she shouldn't lose her "boobs and bum".
Bertolli made it to the top twelve contestants in The X Factor but was voted into the bottom two this week alongside Jacqui Newland. Mel B then chose to save her other protegée Newland over Bertolli because she thought she was better at controlling her nerves on stage.
Newland was in the bottom two the week before with Cleo Howman, but Howman was sent home after performing Christina Perri's 'Jar of Hearts'. She later described her performance as a "nightmare".
Eliminated contestant Luke O'Dell, whose audition on The X Factor Australia went viral on the internet, recently slammed Mel B's singing skills after she performed live on stage with co-judges Guy Sebastian, Ronan Keating and Natalie Bassingthwaighte.
> Mel B blasts fellow Aussie 'X Factor' judges
> 'The X Factor's Natalie Bassingthwaighte: 'Mel B needs a slap'
Watch Tyla Bertolli perform on this week's The X Factor below: