The curvaceous star confessed through her Twitter page that she had not been working out for the past two months.
She took the long break from exercise to shoot Kourtney and Kim Take New York in NYC.
But now Kim has returned to the gym.
"I hit the gym hard today!!!! I fell off for 8 weeks in NYC BUT IM BAAAACKKKK!" she Tweeted Saturday.
The 5' 2" reality star - who said she was a size 2 a few months ago - has long talked about her curves, which she recently told UsMagazine.com she has learned to love more since turning 30 in October.
"I never knew how to embrace curves," said Kardashian, who is reportedly now dating Halle Berry's ex, Gabriel Aubry.
"I looked at my aunt and cousins and saw these Armenian women with big butts and boobs, and I didn't really realise how attractive it actually was then. Your perspective grows."