"It went past being hungry; it was actually painful in your stomach. I could feel my intestines twisting in the middle of the night."

What might be less familiar to his millions of fans is what he went through to reach the pinnacle of his sport - and how he continues to be "fighting battles" to this day.

The Springboks' first black captain was brought up in a township in Zwide, Port Elizabeth, where he experienced hunger and violence as a child.

After being given a scholarship to a white school, he developed his rugby skills on the pitch and opportunities opened up for him.

Now - after the release of his autobiography Rise - Kolisi spoke to BBC sports editor Dan Roan for The Sports Desk podcast, explaining that he wants to be known for much more than his sporting achievements.

In a wide-ranging interview, Kolisi revealed:

'I would scream with hunger' - Kolisi on childhood

Speaking to BBC Sport from his family's home in Durban, Kolisi paints a vivid picture of the hunger he suffered as a child.

"It went past being hungry; it was actually painful in your stomach," he says.

"I could feel my intestines twisting in the middle of the night. I would scream to my grandmother and she would get me sugar water and it would settle it down.

"A lot of my values come from being resilient. The people from my community might be poor financially but they are happy, proud and resilient people.

"When I dropped food parcels off, they didn't like that. They want to work for what they have. That's what has taught me never to complain.

"If someone told me I can't do it, I would keep on going until I make it.

"I was living in survival mode when I was young. I'm now trying to teach the people to live in a mentality that they can be whatever they want to be even though the situation around them is hopeless."

Kolisi now campaigns against gender-based violence, another issue that scarred his childhood.

"At home, like right next to me while I was sleeping, I'd wake up hearing the screaming of my mum or my aunt," he says.

"Or I'd be walking to school and seeing someone getting beaten in the middle of the street and no-one doing anything about it because people felt it wasn't their business.

"Men don't speak about it, but men are the problem. Men are not protesting this, men are not asking the government to change. There are men that do, but it's always women [who protest].

"I couldn't make a difference for my mum or for my aunt. But now I have a voice. I want to be one of the people that makes change, because I want change.

"We can influence so many people. People will listen to us when they might not listen to politicians. I don't want my kids to battle with what I have.

"The sport is not who we are, it's what we do. You have to use your voice where you can because you don't know whose life you could be saving."

'We received a lot of hate at the start of our relationship' - on social media abuse

Kolisi says he and his wife Rachel, who is white, have been the target of racially motivated abuse.

They endured "a lot of hate" at the start of their relationship, with insults about his wife "wasting good genes for marrying me", Kolisi recalls.

"That stuff hurts," he says. "She took it very hard. That stuff should be addressed. People say you should take the good and the bad. No, I would rather have none of them.

"There's some stuff you can't handle. You shouldn't be getting that kind of hate. Everyone can have their opinions but can keep it to themselves. People should stand up a bit more. We work hard every day. You're not always going to win everything or perform.

"To have someone swear at you and your family because of your skin colour... I saw it in the Euros final [when England lost to Italy and players were racially abused online]. I knew it was going to happen. People are not surprised any more. Then they celebrate when you're doing well.

"The social media groups should protect athletes and cut people off. When people do a horrible job in their work, no one gets to say those things to them."

Like many athletes, Kolisi publicly backed the Black Lives Matter movement in 2020 following the killing of George Floyd in Minneapolis, despite some opposition.

"Some people just don't understand," he says. "They don't like what the movement is about.

"I told my story and tried to make people understand. All I'm saying is 'let's create a fair opportunity for everyone'. Sometimes I felt that my life didn't matter growing up. All you think about is survival and not about thriving in life.

"I know the message I was trying to say and those that heard me, heard me, and that's all that matters."

'We're not robots' - on athletes' mental health

Kolisi is heartened by the fact that sports stars are increasingly prepared to speak publicly about their mental health - notably tennis player Naomi Osaka, who pulled out of the French Open in May to prioritise her mental well-being, and US gymnast Simone Biles, who withdrew from a number of events at the Tokyo Olympics in July and August for the same reason.

"I took so much from Osaka," Kolisi says. "For her to stand up and say 'listen, I'm not OK'... that makes me feel OK about not feeling OK sometimes.

"To hear someone that you look up to and someone that you watch, that touches you.

"It makes me feel so good to know that it's right for me to go through this kind of thing.

"We are trained to not show pain in the sport that I play. We are trained that when you get hurt, you must just get up and keep on moving forward and sometimes you take that literally.

"Even when you're not OK personally, emotionally… In my culture, men don't cry. That's absolutely rubbish…. We're not robots, that's the ultimate thing."

'I'm a sinner' - Kolisi on his flaws

Despite the legendary status he now enjoys around the world, the trailblazing Kolisi readily admits he is far from perfect, and has turned to alcohol in the past to deal with childhood trauma.

"People see me as flawless," he said. "Some look at me as this god. On social media, you don't post stuff about all the struggles that you have, and we only show the good times. My wife and I call it the 'highlights reel'.

"But, I've also got a responsibility to not just young people, but everyone. People my age who are struggling with stuff.

"They look at me thinking: 'He's perfect. How can I get there if I'm struggling with this?' They don't know that I'm fighting battles… I wanted to show [in 'Rise'] that it's OK for you to go and get help when you need help."

The Springboks captain credits those closest to him for supporting him in his battle with mental health, and urged others to seek out help for themselves.

"I had to go and get help with this stuff," he says. "Rather than the thing killing you, go and help yourself before it's too late.

"I want people to know that I'm a sinner and I was just trying to be better each and every single day. I will never be perfect, 100% be perfect, but I'm still enough as I am."

'It's a daily struggle' - on unity in South Africa

Kolisi, who was a part of the racially diverse South Africa team who defeated the British and Irish Lions this summer, captained the Springboks as they won the Rugby World Cup in 2019, defeating England 32-12 in the final.

"I can't tell you if it has unified people but it's made people happy," he says. "We want to be as unified as we can. It's a daily struggle, hopefully we will get there one day. But those moments give a lot of people hope, people can relate to each individual."

So how does he feel when comparisons are made between the 2019 victory and South Africa's Rugby World Cup triumph on home soil in 1995, when Nelson Mandela, the country's first black president, wore a Springboks jersey as he presented the trophy to captain Francois Pienaar?

"It's all about what you do with those moments," says Kolisi.

"I remember the night before the final, my wife and I were sitting thinking about how we could help other people."

Kolisi will lead South Africa in next month's autumn internationals, facing old foes England for the first time since that 2019 final. The Springboks will also play Wales and Scotland.

"Every time we play England, it's always tough," he says. "We're looking forward to it but we can't look past Wales though. We haven't beaten Wales there for a long time and Scotland are on a high, doing very well."