The 29-year-old singer-and-actress has shed 80lbs and dropped five dress sizes and admits she is so happy with the way she has transformed her figure, she values the achievement more than scooping the Best Supporting Actress Academy Award for `Dreamgirls` in 2007.
She said: "I`m prouder of my weight loss than my Oscar!"
Jennifer - who shot to fame after appearing on `American Idol` in 2004 - was inspired to lose weight during her pregnancy with son David, now two.
She explained in the new issue of Self magazine: "I thought, hold on - why doesn`t anybody know I`m pregnant? And I wanted to set a good example for my son."
Despite her pride in her weight loss, Jennifer - who is engaged to David`s father, WWE wrestler David Otunga - claims she wasn`t aware she was overweight until she moved to Hollywood.
She said: "I didn`t even know I was considered plus-sized until I came to Hollywood. I thought I was the perfect size!
"[One day] an interviewer asked, `How does it feel to be plus-sized in Hollywood?` I looked around, like, `Who is she talking to? Oh, me? I`m plus-sized?` In the neighbourhood I`m from in Chicago, a 16 is normal. But in Hollywood, everyone looks exactly the same, so I stood out."