Kim - who gave birth to daughter North in June - has been following the diet to lose the weight she gained during her pregnancy.
Tweeting about her eating regime, Kim said: 'I've actually been doing the Atkins diet & luv it'.
The controversial diet plan – which has followers eating lots of protein and fat in place of carbs – was developed by Dr Robert C Atkins in the 1950s. It had a huge following in 2003 and 2004, with many celebs extolling its virtues. Critics of the diet however, claimed it was unbalanced, and too high in saturated fat and red meat.
A rep for Atkins told the Mail that Kim is eating 'lots of lean proteins, healthy fats like nuts and avocado, carbs, fruits, veggies and cheese'.
"She wanted to be a healthy, nursing mom and not toxify her milk with her diet or lose weight too quickly. She's been doing Atkins since her doctor approved it at the end of June," the spokesperson added.
Back in March, while six months pregnant, Kim spoke about her much-publicised pregnancy weight on the Extra show: "There are maybe two or three covers just this week that say I am 200 pounds,' she said. "I'm like, "You are 60 pounds off here'."