Carey developed gestational diabetes and severe edema during her pregnancy, which she said caused her to gain a significant amount of weight.
"Edema was the probably the most painful thing I went through during my pregnancy. My legs looked three times the size of what my legs do right now. I thought I would never be the same person again," she told USA Today.
"I was walking around the house, pregnant and miserable, looking at mirrors and saying: 'Why did I put so many mirrors in my house?'"
The 'Obsessed' singer partnered with diet company Jenny Craig in a bid to become healthier after giving birth to her and husband Nick Cannon's twins Monroe and Moroccan in April.
Carey said that she lost quite a lot of weight after having her twins, but used Jenny Craig's eating plan to drop an additional 30lbs.
"I feel better in every way. To me, it's mind, body and soul. I was in a bad place physically during my pregnancy," she said.
Carey will star in a series of television advertisements featuring her US top five hit 'Make it Happen' for Jenny Craig.
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Watch Mariah Carey's first Jenny Craig commercial below: