Carrie Underwood Actually Enjoys Counting Calories to Stay Healthy: ‘I Love Rules'

Carrie Underwood is opening up about why it’s crucial for her to have structure in her health routine.

The 36-year-old singer covers the April issue of Women’s Health, where she talks about maintaining her health regimen and practicing her own version of self-care.

After years of experimenting with counting calories and macros, Underwood said she has figured out the ratio that works best for her: 45 percent carbs, 30 percent fat and 25 percent protein.

“I love rules,” she told the magazine, referring to tracking her nutrition. “This is how I feel good about myself, and this is how I operate.”

However, the “Blown Away” artist admitted to struggling with counting calories, reading labels and overexercising when first on tour after winning American Idol in 2005.

RELATED: Carrie Underwood on Refocusing Her Fitness Routine: ‘It’s Less About Trying to Stay Thin’

“I would ‘fall off the wagon,’ then feel terrible and repeat the cycle,” she explained, adding that she would sometimes eat as few as 800 calories a day. “Your body is screaming ‘I need more calories. I need more carbs!’ ”

Now, the mom of two maintains a healthy diet — but still occasionally indulges in her “vice” of red wine while watching The Bachelor — and hits the gym to practice self-care.

“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 said, explaining why she tries to squeeze in a sweat session whenever possible.

Underwood also stressed the importance of planning ahead before going to the gym.

“When I walk in and don’t have a plan, I usually walk out,” she told the outlet.

The singer expressed that she likes to “set goals” to get through a cardio workout — for example, she’ll tell herself, “Every 15 minutes I’m going to hit 1.25 miles, then by the end of an hour I’ll have run 5 miles.”

RELATED: Carrie Underwood on Her Line CALIA’s Commitment to Inclusivity: ‘We’re Not All Size 0’

For Underwood, though, her passion for health and wellness is about much more than wanting to “stay thin” she told PEOPLE at the CALIA by Carrie Underwood Aspen Getaway in December.

“It’s been more about health, and being strong, and setting a good example for my kids, and working out because it makes me feel good,” Underwood, who shares sons Isaiah Michael, 5, and Jacob Bryan, 13 months, with husband Mike Fisher, said. “And just kind of shifting my mindset about why I’m into health and fitness.”

And as for her toned figure, Underwood works hard but doesn’t deny that genetics play a factor (especially when it comes to her famous leg muscles!) “I think just in life and my body makeup, I’m just kind of a quad-dominant person,” she said.

The April issue of Women’s Health hits stands March 17.