Carrie Underwood loves following rules to stay fit and healthy.
The 36-year-old country singer follows a strictly planned diet that is comprised of 45 per cent carbs, 30 per cent fat and 25 per cent protein but she insists she enjoys counting calories unlike most people.
In an interview with the April issue of Women's Health magazine - of which she is the cover star - she said: "I love rules. This is how I feel good about myself, and this is how I operate."
Carrie didn't always find it fun eating a controlled diet and when she first went on tour in 2005 after winning 'American Idol' she would "fall off the wagon" and eat junk food.
She shared: "I would 'fall off the wagon' then feel terrible and repeat the cycle."
Revealing that sometimes she would eat no more than 800 calories a day back then, she said: "Your body is screaming 'I need more calories. I need more carbs!'"
Carrie - who has 14-month-old son Jacob and four-year-old son Isaiah, with her husband Mike Fisher - will work out seven days a week if she can because the next week she may find her gym time limited.
She said: "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. When I walk in and don't have a plan, I usually walk out."
The April issue of Women's Health magazine is available from March 17.