Kim Kardashian says "haters" motivate her to stay in shape.

The 33-year-old reality star welcomed her first child, North, with fiancé Kanye West last June.

Kim ruled tabloid headlines during her pregnancy and for months afterward, with critics analysing every pound she gained.

And the star admits reading about her battle to lose the baby weight has kept her in the gym.

Asked by a fan on Twitter about getting in shape after "Nori", Kim wrote: "The haters helped motivate me. Seeing every crazy thing written about me gave me motivation, but its just my personality to want to be fit, not be lazy, and I'm glad I found the Atkins diet which was a challenge (any diet is), but this was the easiest diet I researched, so it allowed me to lose weight fast and not starve."

Kim was keeping up with fans as she watched the season nine premiere of Keeping Up With the Kardashians Sunday night.

She said catching glimpses of herself on the small screen after giving birth to her daughter was also an eye-opener.

"Its crazy because seeing myself back this episode I just had my baby girl and I still hadn't lost my weight yet. It reminds me of all of the hard work I put in, and shows me to not stop working out to live a healthy lifestyle," she continued (sic).

Asked by another fan about her favourite moments this season, she said viewers can expect more drama than ever.
Aside from her own engagement and starting a family, Kim hinted audiences will also get a behind-the-scenes look at what led her sister, Khloé, to file for divorce from Lamar Odom.

"This season is filled with so many unexpected things," she wrote. "So much family support is needed and our real strength is put to the test."