The British pop star found himself addicted to prescription pills and booze as he tried to handle the pressures of life in the spotlight, and having to spend days cooped up in their hotel rooms while on tour only fuelled his habit.
Liam recalls seeing photos of his bloated figure on a boat, and explained on Steven Bartlett's "Diary of a CEO" podcast, "My face was 10 times bigger than it is now. The problem was, the best way to secure us was to lock us in a room, and what is in the room? A minibar."
The singer admits he would often throw a big party for himself "that seemed to carry on for years," and his substance abuse issues soon led to him experiencing suicidal tendencies.
Asked if the difficult time led to suicidal ideation, Liam said, "Yeah. There is definitely some stuff I have never spoken about to do with it (addiction). It was really, really severe."
It's unclear exactly when Liam went through his "pills and booze phase," but he was just 16 when One Direction launched.
They went on an indefinite hiatus in 2015, and the star previously confessed to turning to alcohol to deal with the transition, before embracing a sober lifestyle for a year, with the help of therapy and support from former addict Russell Brand.
Liam recently decided he was in need of another detox after recognising he was becoming more and more reliant on alcohol to pull him through the COVID-19 shutdown.
"I did worry (about alcohol consumption) up until the last few months," he shared. "I think a lot of people had this same sort of thing, alcohol. It was getting earlier and earlier and easier and easier to go to..."
He also ended up piling on the pounds while having to spend day after day stuck at home, confessing he was "disappointed" with himself when he saw clips from a performance at the BAFTA Film Awards in April (21).
Speaking about his general fitness, he said: "I put on so much weight. I was eating badly..."
"I put a lot of weight on. What got me, I did one performance on TV with the BAFTAs and I was disappointed with myself. I didn't look how I wanted to look. In your own self you know how you feel about it."
"Obviously they say the camera adds 10 pounds and it definitely did. I realised I've let myself go in this (sic)."
Liam, who recently ended his 10-month engagement to model Maya Henry, is now determined to get his personal life back on track, revealing he has been sober for the past month.