Washington DC - Boxing legend Mike Tyson, who tasted both glory and prison in a rollercoaster life and career, spoke out Wednesday about his new role as a healthy-eating ambassador for the Trump administration.

The former heavyweight champ has lent his face to an ad campaign with the slogan "Eat Real Food," as opposed to ultra-processed products that are popular in America. An ad generated by the campaign aired Sunday during the Super Bowl.

"This is the biggest fight of my life," Tyson said Wednesday at an event with Health Secretary Robert F. Kennedy Jr.

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Tyson is a poster child for public rehabilitation from disgrace, as his boxing prowess was marred by a rape conviction and prison stint, as well as a fight in which he bit off part of his opponent's ear.

In the new black and white commercial, Tyson (59) recalls that his sister Denise suffered from obesity and died of a heart attack at age 25.

He recounts a tough childhood battling his own weight issues, eating junk food all the time, and weighing as much as 345 pounds.

"I had so much self-hate," Tyson says in the ad. "I just wanted to kill myself."

"Where I come from is Brownsville, Brooklyn. It's the most violent, poverty-struck neighborhood in the city of New York. And ultra-processed food was just the norm," Tyson said at the event with Kennedy, whose slogan is "Make America Healthy Again."

Among a blizzard of alarming changes to US health policy, including de-emphasizing vaccines, Kennedy last month flipped the American food pyramid upside down to encourage people to eat meat and whole-milk dairy products.

Fiber-rich whole grains like oats are now at the bottom of the chart.

Critics have raised concerns that this change might be a result of lobbying from the agriculture sector.