Oprah Winfrey has been a "steadfast participant" in America's diet culture.

The 70-year-old TV star acknowledges that she's played an influential role in shaping the conversation around diet and health in the US.

Oprah - who has discussed the issue at length throughout her career - said on a YouTube special: "I want to acknowledge that I have been a steadfast participant in this diet culture.

"Through my platforms, through the magazine, through the talk show for 25 years and online, I've been a major contributor to it. I cannot tell you how many weight-loss shows and makeovers I have done and they have been a staple since I've been working in television."

Oprah - who hosted her own TV talk-show for 25 years - admitted to having some regrets about her approach towards the issue.

She shared: "I've shared how that famous wagon of fat on 'The Oprah Show' is one of my biggest regrets. It sent a message that starving yourself with a liquid diet set a standard for people watching that I nor anybody else could uphold.

"The very next day I began to gain the weight back ... That wagon of fat moment was set into motion after years and years of thinking that my struggle with my weight was my fault and it has taken me even up until last week to process the shame I felt privately as my very public yo-yo diet moments became a national joke."

Meanwhile, Oprah previously admitted that she struggled to cope with constant focus on her weight.

The veteran TV star said on 'Shame, Blame And The Weight Loss Revolution': "I was ridiculed on every late-night talk show for 25 years."