Just 8 months after giving birth to son Luca, Hilary Duff is back to wearing skinny jeans — in a size 26!

“Yaaaa bitches! Gabe Johns you’re kickin my ass and it’s paying off! Skinny jeans! lets go!” Duff, 25, tweeted on Nov. 29 with a photo of her tiny post-baby jeans.

In June, the formerchild star told Us she wanted to lose the baby weight in a healthy way. “I think if you ask any pregnant mom, they’re like ‘I want my body back,’ but it takes time,” she said. “It takes nine months for your body to get that way and it’s putting on that weight on purpose.”

PHOTOS: Hilary’s new life as a mom

So, how did she slim down after baby?

Duff teamed up with Johns, an Los Angeles-based personal trainer and boxing instructor, two and a half months ago. “Hilary and Gabe have been doing everything from boxing to two-a-day workouts incorporating wind sprints and jump roping in an effort to finally shed the baby weight,” a rep for Johns tells Us Weekly. “Hilary’s been steadily dropping pounds each week.”

On Oct. 31, Duff tweeted, “My legs are so sore it’s hard to get these walking sticks up the stairs! I hope your happy, Gabe Johns.”

In addition to her workouts, the actress has been following the Fresh Mommy diet plan by Freshology.

The plan is suggested for nursing mothers to ensure proper milk production and uses all-natural proteins. It includes breakfast, fresh fruit, lunch, 3 snacks, dinner and 1 dessert for a total of 2,200 to 2,400 calories per day in a 60-day menu for $59.95 per day.

Sample Menu:

Breakfast: Mixed grains & berries

Dinner: Wild caught halibut with ratatouille

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Desserts: Carrot cake

And Duff didn’t have to worry about husband Mike Comrie‘s dinner either! A “Daddy Dinner” is also available.

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