The singer reveals she had never been completely happy with her figure during her youth and when she started receiving compliments after losing a few pounds, she decided to keep it up.
"I knew that I weighed more than I had ever weighed before," she tells America's People magazine. "But then as soon as you start making little tweaks, people immediately go, 'You look so great!' Then you start wondering, 'How bad did I look before?' Then it's like, 'Well, I guess I should keep on going.' Then you start eating less."
The 32 year old soon started taking weight-loss supplements to help keep her figure trim and she now realises how unhealthy her lifestyle had become: "I was taking things with (herbal medicine) ephedra in it. It wasn't the best way. If I could go back and talk to myself I'd be like, 'Here's how you do it the right way.'"
However, Carrie insists her dieting never turned into a real problem, stating, "None of it was intentional, you know? I wasn't eating enough calories, but it wasn't because I was trying to starve myself. I just didn't know how many calories I should be eating."
The mother-of-one has since become a strict vegan and is regularly hitting the gym to stay in shape, and she believes she has never looked better since giving birth to son Isaiah earlier this year (15).
"For some reason, I feel leaner after," she says. "It's really strange the way my body has reacted to exercise after having him. I feel like my bum's a little nicer than it used to be."
But there is one part of her body that will never be the same after undergoing a Caesarean section - the small four-leaf clover tattoo on her abdomen: It's not really a four-leaf clover anymore, it's a multi-leaf. It doesn't match up with the top! And I think most people deal with this after a C-section, there's like a little pooch over the scar. It's something that I'm probably going to have forever."