Guy Sebastian has opened up about a chance interaction with a fan that moved him to tears.

The pop star, 43, appeared on the latest episode of the ABC iView series The Assembly, where he made the candid admission.

Guy was answering questions from a group of autistic journalism students when one asked for advice on how to deal with trolls.

‘You have recently talked about being fat-shamed while being on Australian Idol,’ the student asked.

‘If you could talk to your younger self, what would you say to them and what advice would you give to me or anyone else struggling from this?’

Choosing to answer the question more broadly, Guy then revealed he was approached by a long-time fan after hitting back at a troll on social media.

Guy Sebastian has opened up about a chance interaction with a fan that moved him to tears

‘I remember I responded to a troll on social media. Someone said something awful to me and I sent them a message back,’ he said.

‘One of my fans wrote to me and said: “Guy, I’ve sent you over 100 messages and I’ve never had a response, yet this troll who doesn’t follow you throws shade at you and gets your attention.’

Guy said the moment brought him to tears and made him reassess where he focused his energy.

‘Something broke in me. I burst into tears,’ he said.

‘I felt this deep shame in where I was directing my energy.  It’s a daily reminder to wake up and think: “Am I going to devote my energy to the people who love me? Or am I going to waste it on people who aren’t in my corner?”‘

Guy recently discussed his battle to maintain a healthy weight since his rise to stardom 20 years ago on the Mental as Anyone podcast in June last year.

‘I was the fat kid on Idol, I was called the fat kid… I was just a bit chubby,’ Guy admitted.

‘I was pretty unhealthy, I would binge eat [and] my approach to losing weight was pretty extreme and I would just get nowhere.’

Guy was fielding questions from a room of Autistic journalism students on the ABC iView series The Assembly when one asked for advice on how to deal with fat-shaming trolls

After revealing that he had once responded to a troll who sent him a nasty message online, Guy added: ‘One of my fans wrote to me and said: “Guy I’ve sent you over 100 messages and I’ve never had a response yet this troll who doesn’t follow you throws shade at you and gets your attention?”‘

He told host Jonathon Moran that ‘criticism’ directed at him both externally and internally was behind his unhealthy eating habits.

‘I think what I didn’t do was acknowledge it, and that goes for heaps of stuff I’ve had to overcome,’ he said.

‘I realised when I would eat a lot… it was around times of criticism.’

Guy’s admission comes after he recently shared a shocking health update after he underwent two spinal surgeries in one week last month to treat ‘nerve pain’.

He revealed in August that he was suffering from severe pain when he shared a post-surgery photo of himself on Instagram.

He appeared on Sunrise earlier this month to assure fans he was ‘on the mend’ after the hellish procedure, but was still waiting for feeling to come back in his fingers.

‘I’m alright. It’s been hell, to be honest. It got to a point where I just couldn’t take the pain anymore,’ he told hosts Natalie Barr and Matt ‘Shirvo’ Shirvington.

‘I had no feeling in my hand. I was dropping my guitar picks. I knew something needed to be done.

Guy admitted that the revelation had moved him to tears, as well as forcing him to reevaluate where he placed his energy. Guy is pictured performing at the AFL Grand final in 2004

‘Something broke in me. I burst into tears,’ he said. ‘I felt this deep shame in where I was directing my energy. It’s a daily reminder to wake up and think: ‘am I going to devote my energy to the people who love me? Or am I going to waste it on people who aren’t in my corner?’

‘I had surgery, and I was one of the rare cases of needing to have it again. So, I had two spinal surgeries within a week. It was hell. But I’m on the mend now.’

‘I knew I had to get everything good because I’m touring next year, for the most part of next year. Yeah, it’s been a rough few weeks, I can’t lie about that,’ he added.

When Nat and Shirvo asked if feeling had returned to his hand, the hitmaker admitted he still couldn’t feel his thumb, index finger, and middle finger ‘all the way through’.

‘[But] the pain is gone. I’m so grateful. I’m one of the lucky ones to be able to get surgery,’ he added.

It’s certainly been a rough year for Guy, health-wise, with the Australian Idol star kicking off the year with a shocking ski accident.

Then, in May, Guy was rushed to hospital after he suffered another shocking injury that saw him require surgery for a ruptured Achilles tendon.

The incident occurred after Guy teamed up with AFL great and radio host Brendan Fevola to help struggling club Masala Dandenong break a long losing streak.