08/16/2011 at 09:00 AM EDT
It wasn't until Jennifer Hudson
appeared on American Idol
in 2004 that
she was made aware of her weight
"I didn't even know I was considered plus-sized until I came to Hollywood," the 2007 Oscar winner
and Weight Watchers spokesperson
, 29, tells September's Self magazine
, on sale Thursday. "I thought I was the perfect size!"
That changed on a red carpet, when "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 neighborhood I'm from in Chicago, a 16 is normal. But in Hollywood, everyone looks exactly the same, so I stood out."
Hudson decided to take action when she was pregnant with her now 2-year-old son, David
"I thought, hold on – why doesn't anybody know I'm pregnant?" she admits. "And I wanted to set a good example for my son."
By sticking to a strict regimen
of portion control and exercise, Hudson eventually lost 80 pounds and went from a size 16 to a 6 and says: "I'm prouder of my weight loss than my Oscar!"