A lot of the negative comments, she said, were focused on her body.
"I didn't really realize that I was 'the fat sister' if you will until I went on TV and the media started saying that about me," she told People magazine. "I started saying it before people. I was like, 'Okay, I'm the fat, funny sister. Who cares?' I almost let that take ownership of me. [But really] I wasn't fat. I wasn't obese. But I would let society make me believe that I was."
Growing up, Kardashian, 31, said she was "chubby," but lost weight as a teenager. Throughout the years, regardless of her size, the reality TV star said she always felt good about her looks.
"I knew I didn't look like my sisters and I didn't have those shapes, but I didn't think that was wrong," she said. "I had parents who were incredibly loving and nurturing and always made me feel beautiful so I never really questioned that."
Recently, however, she's been committed to regular workouts and clean eating. Though she doesn't weigh herself, she guessed she's lost about 40 lbs. in recent months.
"I don't believe in numbers," she said. "I don't believe in one size fits all. As long as I can lay my head down at night, that's all that matters. It's not about fitting someone else's standards."