Khloé Kardashian Opens Up About Body Image Issues: I Was Always the 'Fat Sister'

Khloé Kardashian is breaking her silence about her bedside vigil after Lamar Odom was found unconscious. Subscribe now for this exclusive interview, only in PEOPLE!

It takes a strong person to withstand repeated attacks on your physical appearance. And as shown by Khloé Kardashian‘s unwavering support of ex Lamar Odom as he recovers from a devastating overdose, this reality star and entrepreneur has learned many a lesson from her past.

“Growing up, I was always chubby,” Khloé tells PEOPLE exclusively in this week’s issue. “My girlfriends were always running around in two-pieces and I never felt comfortable to do that.”

Still, the Keeping up with the Kardashians star says she felt comfortable in her own skin, despite the fact that she had a different body type than her two older sisters, Kourtney, 36 and Kim, 35.

Says Khloé: “I knew I didn’t look like my sisters and I didn’t have those shapes, but I didn’t think that was wrong. I had parents who were incredibly loving and nurturing and always made me feel beautiful so I never really questioned that.”

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However, when their E! show became a smash overnight success, Khloé was thrust into the spotlight – and the attention could get ugly. “Right before the show started, I thought I was in good shape, but I guess not good enough for Hollywood’s eyes,” she says. “I didn’t realize I was the ‘fat’ sister until I went on TV and the media started saying that about me.”

Continues Khloé: “Being compared to my sisters was something I was used to. But being compared in such a harsh way I just thought, ‘Okay, that’s my role.’ So 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. [In reality] I wasn’t fat; I wasn’t obese. But I would let society make me believe that I was.”

• For much more from Khloe, including an exclusive interview and book excerpt in which she talks about the sad demise of her marriage, her body image struggles and the impact Lamar’s problems have had on her brother Rob, pick up the new issue of People, on newsstands Friday

Now, the author – whose new book, Strong Looks Better Naked, is on stands Nov. 3 – says she doesn’t weigh herself, though she estimates that she’s lost about 40 lbs. thanks to a healthy commitment to eating right and regular, intense workouts.

“I don’t believe in numbers,” says Khloé. “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.”