Legs for Days! Carrie Underwood's Most Important Fitness & Diet Secrets

Sometimes whipping up breakfast seems unrealistic most mornings, and that's okay — it happens to the best of us, including the country crooner. She told Cosmopolitan: "I stock up on frozen breakfast burritos just in case I'm making something for [2-year-old son] Isaiah and run out of steam before I can make something for myself."

Though the superstar singer is known for her sculpted legs, she admitted in an interview with E! that she isn't working out as much as she used to — and she's fine with that. “I used to work out six days a week,” Underwood shared. “But now that’s a little rare, sometimes it’s one or two times a week and that just kind of has to be okay. And it is okay because whatever I’m doing that’s keeping me out of the gym is important.”

"This is what people come to me for. Carrie Underwood has beautiful legs," her trainer Erin Oprea told PEOPLE. "That's what I love doing. So here's one thing I find absolutely so useful – lunges."

"We hardly ever takeout or eat out because I don't like to," she revealed to Cosmopolitan. "It's not that I'm an amazing chef — I stick to the basics, like roasted veggies and stir-fries — but I like knowing what's in my food, and it's hard to tell when someone else makes it for you."

The rule will come in handy when you're just not feeling a full-blown workout. As for what Underwood does? "I can go run for a little while, I can go do some tabata rounds, I can do something," the singer told PEOPLE. "Sometimes I'm like, my workout today is going be running around after my kid. If we're going to go to the park, why not run there and push him in the stroller? Then I get a good cardio session to and from, and then he gets to play, so everybody wins."

"I've gotten a lot better at doing what I can when I can, but also cutting myself a little slack," she told PEOPLE. "You have to!"

"I've kept a food journal forever, since I'm a bottomless pit, and I can out-eat everyone I know," Underwood told Cosmopolitan. "It's like there's no sensor between my stomach and brain that says, 'Hey, you're full, stop eating!' Once I recognized that about myself, I started tracking my diet, which helps me make better choices and pay attention to what I'm eating. I also write down which exercises I'm going to do later on."

"I 'play cards' a lot," she told PEOPLE. "I assign different exercises to each suit, and I sit down at breakfast and plan out what each suit's going to be." As for what those exercise moves could be, the singer has opted for tuck jumps, burpees, overhead lunges and more.

The singer's son, Isaiah, is a total yogi-in-the-making — and Underwood is all about it.

"I wasn't eating enough calories, but it wasn't because I was trying to starve myself," she told PEOPLE of how she handled her health and fitness over a decade ago. "I just didn't know how many calories I should be eating." The strict vegan, who hits the gym for 90 minutes at a time whenever she can, added: "I weigh more than I did when I was at my smallest, but I have a lot more muscle tone."

Truth: A new set of stylish exercise gear can be the ultimate motivator. "I used to go to the gym in ratty old sweats, but if you already feel good going into your workout, it just kind of gives you that little extra lift," she shared.

"It's all about realizing why you do it," she told PEOPLE of staying body positive. "I want to be a great mom and I want to be around for him for as long as I possibly can. I want to feel good about myself, I want to set that example for my child and make that a priority, because he's watching."