Jessica Simpson is reportedly committed to "healthy, long-term weight loss".
The fashion mogul welcomed daughter Maxwell on May 1 and signed on to be a spokeswoman for Weight Watchers.
The 32-year-old star gained around 70lbs during her pregnancy and was estimated to weigh around 180lbs.
Jessica is said to be ecstatic with the results she's achieving.
"She loves this diet because there aren't any foods that are off limits," a source told the US edition of OK! magazine.
"For healthy, long-term weight loss, she's been told to use most of her points on lean protein and fruits and veggies, but if she craves a treat she can have it. Indulging once a week is actually encouraged, which Jess loves.
"Jessica has been sticking to her programme like a pro. She's doing the Weight Watchers points programme and she's got a notebook that she uses to write down everything she eats."
Jessica is said to have lost a significant amount of weight since she began her dieting and fitness regimen a few months ago.
"She's so happy that it's paying off because at her last weigh-in, she was down to 153 pounds!" the source said.
© Cover Media