The Only Way Is Essex star underwent the "gruesome" procedure last month. Speaking to Now magazine, Sims recalled the "exact moment" she began "to hate my bum".
Before and after: Sims shows off the results of her butt lift
"I was 18 and I'd just bought a tight satin boob tube dress. But when I tried it on and saw how flat my bum looked I was devastated," she said. "I know it sounds trivial but I've always hated my figure. Even before I was in The Only Way Is Essex I was surrounded by gorgeous girls with hourglass figures. Mine felt unsexy and boyish in comparison.
"I know there are more important things in life, like having good health, but I just couldn't help it. I tried everything possible to overcome my body insecurities. I wore certain clothes to make my bum look bigger and even wore knickers with chicken fillet-type padding."
Describing it as a "flat granny bum", Sims said that she had "seriously considered" getting implants, but instead opted for a "safer and more natural" Brazilian Butt Lift, which saw fat from her stomach and thighs injected back into her bum.
"My bum doesn't feel heavier or wobblier like I thought it would. But it does look lifted and now goes into a noticeable bum shape, which I'm really happy with," she said. "Obviously my belly and legs look slimmer because they took the fat from there.
"The downside is that I felt sore for a few days afterwards and I'm not able to lie on my back for six weeks in order to let the fat on my bum settle. I don't want to lie on it and squash it all round the wrong way – imagine!"
Sims, above left, pictured arriving in Los Angeles last week with co-star Lauren Pope
Sims continued: "People sometimes have a go at me for being full-on 'plastic' and they think I've had it all done - but they couldn't be more wrong. I've only had two boob jobs, teeth veneers and then this. I don't think I need to have anything else done now.
"Hopefully, if I continue to eat the same, I'll get them back – then I'll have thighs and a bum and I'll look more womanly," the 30-year-old added. "It's sexier to have a bit of weight on you, isn't it? It's not sexy to be skinny with no bottom."
Read the full feature in Now magazine - out today.
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