02/13/2012 02:22 pm ET | Updated Feb 14, 2012

Rebecca Romijn On Losing Baby Weight: 'Hardest Thing I've Ever Done' (PHOTOS)

Pregnancy may be the only Hollywood-approved reason an actress can gain weight, but it often seems as if she's expected to drop the baby weight just as soon as she's left the hospital.

While many celebrity moms are back in fighting shape mere weeks after giving birth, Rebecca Romijn tells Fitness magazine that dropping the 60 pounds she gained with twin daughters Dolly and Charlie, now 3, was a real struggle.

Though she told "Extra" in 2009 she dropped the first 35 pounds without trying, she recently told Fitness, "Losing that weight was probably the hardest thing I've ever done in my life. I had to change the way I worked out, the way I ate -- everything."

Romijn, who stars in the upcoming Tyler Perry comedy "Good Deeds," explained that everything she did to stay in shape before she was pregnant -- like Pilates -- didn't work for her anymore. "A friend suggested I try Bikram yoga. At first the idea of doing a 90-minute workout in a 105-degree room sounded like torture," she said. "But the sweating is exactly what I became addicted to. My body changed dramatically almost immediately. Within three classes I noticed less belly fat."

Being camera-ready means doing Bikram yoga three days a week, says Romijn, who jokes that running after her twin girls is a workout in itself. The 39-year-old also admits she feels guilty leaving her girls to work out, calling it a "huge challenge."

"Mother's guilt is no joke! I feel it every time I leave them to go exercise," she confessed. "Now that the girls are in preschool, it's easier. I go as soon as I drop them off at school. As a mom it's very important to take care of yourself physically and mentally .... There are days when I rush out to a yoga class just as I'm starting to feel like I might be losing my mind."

Romijn also says she got her pre-baby body back by changing the way she eats. "I went on a major diet about eight months ago. I cut out starch, dairy, fat, red meat, alcohol and sugar," she said, explaining that she eats lots of lean fish and salads. "Eventually I started having red meat again, and that's when I got the biggest energy surge."


Check out some photos of stars' post-baby bodies below:

Before/After Pregnant Stars