The country star has been the centre of controversy since she was photographed looking "scarily skinny" in early 2011, though she has insisted that her weight loss was a "natural process".
Appearing on Chelsea Lately, Rimes again confronted rumours that her new, slim figure was the result of an eating disorder or other unnatural methods, claiming that "baby fat" was behind her former figure.
"I was a baby. You've known me since I was 13. I was fat. Baby fat... and then, I grew up," she said. "I'm about to hit 30 this year. I heard it's all downhill from there."
Rimes was also questioned about the fact that she and husband Eddie Cibrian are heavily photographed by the paparazzi, with Rimes often pictured wearing a bikini.
"I am on the damn beach, for God's sake... they follow us everywhere, it's quite annoying. I'm annoyed with myself, to be honest," she said.
Rimes has previously confessed that she is hurt by criticism about her body.
Watch LeAnn Rimes on Chelsea Lately below: