12/11/2013 at 06:00 AM EST
After revealing her post-baby body in a sexy Instagram selfie
in mid-October, Kim
has been wowing with figure-flaunting fashions ever since.
But since setting out on the road with fiancé Kanye
West on his Yeezus tour
, the reality mogul and new mom
has vowed to stick to her carb-free Atkins diet.
With the help of "a trainer on tour with she and Kanye and a chef to keep her meals carb free," Kardashian, 33, has managed to slim down even more, says an insider.
"With the exception of some cheat days, because she is realistic now, she sticks with it!"
When she's not busy with new mom duties to North, 6 months
, "Kim is working out almost every day," explains the insider. "It's usually running and weight training."
Acknowledging that losing her baby weight
was one of the hardest things she's ever done, Kardashian, says the insider, knows that keeping her fit frame will require constant work.
"It's hard, but she sticks with it pretty much all the time," says the source. "She's so happy. Life is good."