The former X Factor winner admitted that in the past, she has slimmed down too much and sparked her mother's concern.
But the Trouble star, 27, added that as she's grown older she's learnt to accept her natural shape.
"I've done every kind of diet. When I was in my late teens I was a size eight (and I'm 5ft 8in) and thought I was fat and mum had to say to me, 'Don't lose any more weight.' Looking at pictures now, I can see I was sickly skinny," she told the latest issue of British Marie Claire. "[I have learnt] that it's OK to have imperfections. I feel confident in myself now and I'm looking forward to getting older, to a place where I don't care about what people think."
Leona also spoke about her experiences in image-conscious Los Angeles, where she has spent a big part of her career.
The star said she feels there has been a positive shift from the city's obsession with perfect bodies to a more health-conscious mind set.
"The whole being super-skinny thing is so outdated now; it's more about being super-healthy. When I first went to Hollywood six years ago, [I thought] 'I don't want to spend two seconds in this place, everything is plastic,' but it feels different now. I love Los Feliz, which is health conscious but reminds me of Shoreditch - vintage and full of hipsters."