!["I've had to exercise and keep a very, very rigid diet [to lose the baby weight]."](http://cdn2-b.examiner.com/sites/default/files/styles/image_content_width/hash/7f/ff/1360009270_5931_Untitled.jpg?itok=7V__NlAF ""I've had to exercise and keep a very, very rigid diet [to lose the baby weight]."")
Actress Molly Sims showed off her impressive pregnancy weight loss in a bikini photo posted to Twitter. Sims is vacationing with several gal pals in sunny Playa del Carmen, Mexico.
"Finally bikini ready and pulling out those Sports Illustrated Swimsuit poses, just in time for my bestie Lauren Kucerak's big birthday!" Sims wrote in the caption.
Molly, a former model, said losing weight after giving birth to son Brooks in June 2012 has been the hardest thing she has ever done.
"It has been difficult, I'm not going to lie," Sims, 39, told Us. "I've had to exercise and keep a very, very rigid diet. It's the hardest thing I've done. [I can only eat] really lean protein, no salt, no oils."
The 5-foot-10 Molly, who gained 65 pounds while pregnant, is taking thyroid medication because of a condition she developed while carrying her son.
"I developed a thyroid condition during my pregnancy, so I didn't realize why I was gaining so much weight, so now I'm on thyroid medicine," says Sims. "My thyroid kind of shut down, so that really made it very difficult in terms of the weight loss."
Molly is refreshingly candid about her struggle to lose weight postpartum. Actress Nicole Sullivan recently said most celebrities lie about the strict diets they undertake to lose their baby weight.
"They all lie and say, 'Oh, I lost the weight running after the kids or breastfeeding.' It's not true!" said Sullivan, 42.
