The ex-Emmerdale actress, who is partnered with Robin Windsor, said that she joined the BBC ballroom contest to give plus-size women "courage" to flaunt their sexuality.
"I knew exactly what people were thinking when I came on stage - 'Here's the joker'," the Daily Mail quotes her as saying.
"But from the moment I was first asked to take part I was adamant I didn't want to be that person.
"What I wanted to show was that it was okay for someone like me to do a competition like this, to dress in sexy clothes and have fun. There are so many judgements about larger women, even though there are a lot of us.
"People think we're lazy, that we just sit and eat and that's just a massive over-simplification. There's a lot of prejudice attached to it. Many would give their left arm to be thinner. Not me."
Riley also questioned the mentality behind current female beauty trends such as tanning.
"I hate this obsession with looking a certain way," she said. "These days you've got to have your tan, your extensions - it's a sheep mentality.
"It's okay to be orange and fake, but not to be bigger. But who decreed that? And the result is a vast number of women thinking, 'I can't be that', and becoming insular, losing their confidence. And it's wrong."
Riley recently stripped down to a Beyoncé-style leotard for a magazine shoot, in which she joked about looking like the 'Single Ladies' star during her pregnancy.