Earlier this week, new mother Jessica Simpson stepped out and shocked the world with her impressive weight loss and has now revealed the reason behind her motivation to change her body shape.

The singer and presenter gave birth to her first son, Maxwell, back in May and stopped by Katie Couric's new show yesterday (September 10) to talk about shedding the post-baby pounds.

She explained that seeing herself without clothes pushed her to lose the weight: "The easiest way to get motivated is to strip naked and look in the mirror. It's not fun to be talked about. It's not fun to be judged."

She admitted that she's lost around 40lbs so far and credited Weight Watchers with the support she needed to commit to a new healthy lifestyle plan:

"The very first time I got on the scale in my Weight Watchers meeting, my heart was pounding because I had no idea how much I weighed. I was always the girl who stood on the scale backwards because I didn't want to face it."