The prison officer, who wows in glamorous gowns every week, told ITV's Daybreak that she is happy with her new slimmer figure and is determined to continue with her new healthy lifestyle.
"Throughout this competition I've never weighed myself, I weighed myself today for the first time and I've lost over two stone since the first one," she told Richard Arnold.
"When I look back at how I was before, I'm just so happy with the way that I look now and my willpower is just growing so much and I just want to get fit."
Sam will perform her celebrity duet alongside X Factor judge Nicole Scherzinger on this weekend's final. They will sing 'And I'm Telling You'. "Her voice is amazing and her range is out of this world," said Sam. "I can't wait."
Sam will also sing 'Edge of Glory' by Lady Gaga and 'Power of Love' by Jennifer Rush.
She's battling for the X Factor 2013 crown against Nicholas McDonald and Luke Friend. It all kicks off Saturday night (14 December) on ITV with the winner being named on Sunday.
Watch Sam performing 'Listen' by Beyonce in her first audition: