Carrie Underwood is opening up about her past diet. The 36-year-old singer covers the April issue of Women's Health and reveals that, after her 2005 American Idol win, she went on a strict diet and exercise regimen due to some comments made about her size online.
"I shouldn’t care what other people think about me," she says. "I was tired, and I kept buying bigger clothes. I knew I could be better for myself, and I let my haters be my motivators."
For a while, Underwood says she was "sleeping better" and had "more energy" while following her plan, but that changed when she upped the ante on her routine, working out more and only eating 800 calories some days. The extreme nature of her plan led her to "'fall off the wagon, then feel terrible and repeat the cycle."
"Your body is screaming out, 'I need more calories, I need more carbs!'" she says, adding that she "really would not call" her past diet disordered eating.
Now, Underwood is mindful of her diet, tracking both her calories and the amount of protein, carbs and fat she consumes daily. "I love rules. This is how I feel good about myself, and this is how I operate," she explains, before revealing that her "vice" is red wine.
"It’s good for my heart, right?!" she quips.
As for her current workout plan, Underwood says she fits in time to sweat whenever she can, something that's not always easy thanks to being a busy mom with her two boys -- Jacob, 1, and Isaiah, 5. Underwood shares her sons with her husband, Mike Fisher, who she wed in 2010.
"If I can work out seven days a week -- which doesn’t happen, but if I can -- I’m going to. Because the next week, I might get two days," she says. "... I’d love to sit in a bubble bath, but that’s not going to happen. My self-care is my gym time, and that’s a stress reliever for me."
"Physical fitness makes everything else possible," she adds.
Prior to welcoming her second child, Underwood suffered multiple miscarriages. "For my body to not be doing something it was 'supposed to do' was a tough pill to swallow," she says. "It reminded me I’m not in control of everything."
Talking about her miscarriages, though, felt like a "weight lifted off my shoulders."
"It’s not a dirty secret," she says. "It’s something many women go through."
Watch the below for ET's most recent interview with Underwood.