Sorry, I never meant to insinuate that she didn't work her ass off, because honestly, I know she did. I just meant that when you have the kind of resources available to her, she had a lot more opportunity for success.
Also, she probably worked her ass off because of inside and outside influences. I watched a show *hangs my head in shame* where Scott the dick wanted to have sex with her and she told him no and that she felt ugly and fat when she was pregnant. I know it's not uncommon for pregnant women to feel that way, but if she felt that way to the extreme that she wouldn't have sex with him, then the motivation to "get her body back" so she can feel desirable is a huge motivation.
It also probably doesn't help that she's surrounded by thin, materialistic, vain people in her family. Her two youngest sister's are models and hyper thin, her mom has no qualms about telling her kids if they're starting to look a little chunky or not looking their best (I don't know if Kourtney is part of her mom's passing comments about looks and weight, but I can't imagine she would be exempt).