Jessica Simpson has lost over 40 pounds since giving birth to son Ace in June 2013, thanks to a portion-controlled diet and resistance-training workouts.
Jessica showed off her weight loss in a Twitter photo she posted while filming her new ad for Weight Watchers.
Simpson, who gained 70 pounds during her first pregnancy, didn't gain as much weight this time, but still got bigger than she wanted to.
"I didn't gain as much weight in my second pregnancy, but I still gained a lot of weight," Simpson, 33, told ABC News. "Any woman, dealing with their body after pregnancy, you look at yourself and you're like, 'What just happened to me?' "
Jessica is following the Weight Watchers diet plan again, just like she did after giving birth to daughter Maxwell in May 2012. With Weight Watchers, Simpson lost 70 pounds in six months before getting pregnant again (by accident).
Simpson credited the diet program's emphasis on portion control for stemming excess baby-weight gain. "Going into my second pregnancy, I was just like, 'Oh, I can't eat the whole cake. I can just eat a piece of cake,' " said Simpson.
"I didn't limit myself, and I definitely was not on a diet during my pregnancy, but I did stay active and I had Maxwell to chase around because she turned one and started walking, so I was a running pregnant woman."
In addition to diet, Jessica has also been breastfeeding. She works out with a trainer four days a week doing resistance-training, and logs 12,000 steps a day using a pedometer.
Simpson won't reveal how much weight she has lost, but is pleased with her weight-loss progress and tries to focus on short-term goals to stay motivated.
"I'm taking it week by week so I don't get frustrated with myself," she said. "If I had a long-term goal, and that's all I thought about it, it would set me back more.
"Every week, I really try to make sure I stick with my points and get four workouts in. That's my goal this week, and I hope that I can lose from that. If not, I'm going to keep on going and try it the next week. So far, so good."