RMELAN, Syria — Five years ago, Hamza Parvez was a pudgy Islamic State recruit from West London known for his unusual social media posts about kittens, KFC and what passed for fast food in the so-called caliphate.

But as the Islamic State’s territory receded, so did his presence online.

For years, the fate of Abu Hamza al-Britani, as he was known, was unclear. The militant, now 26, ended up alive and held in a prison in northern Syria after surrendering to Kurdish-led forces outside the group’s final stronghold in Baghouz earlier this month.

His previous posts on Twitter, Instagram and Ask.fm in the early days of the caliphate revealed a duality not often seen in the social media traffic from the Islamic State.

He toted a weapon and appeared — at least in his Internet posts — to buy into the militant’s embrace of violence and anti-Western diatribes. Yet he also had an improbable pining for Western junk food, cute kittens and a desire to settle down somewhere, marry and have children.

One purported photo of Parvez — who one British tabloid dubbed “Hungry Hamza” for his frequent posts about food — shows him bearded, armed and eating ice cream in the Iraqi city of Mosul, once held by the Islamic State.

But he also released threatening videos urging British Muslims to abandon their lives and join the fight in what he called the “golden era of jihad.”

Parvez is just one of many former Islamic State fighters and supporters now in custody and claiming contrition as their fate hangs in the balance.

“Regret is not even the word. If there was a stronger word, I would use it,” Parvez, appearing gaunt and clad in loosefitting prison clothes, said of his decision to join the Islamic State five years ago.

He spoke to The Washington Post in an interview at the prison in northern Syria, in the presence of armed guards.

Parvez said he lost 30 kilograms (66 pounds) during his five years in the caliphate.

“What happened was completely horrific,” he said of the group’s tactics. “I don’t think we should ever allow anything or anyone to take Islam as a religion and for them to manipulate it . . . and to shape it the way that they shaped it.”

Such apparent remorse is unlikely to sway Britain’s government, which says it will not repatriate British nationals who traveled to join the Islamic State. Thousands of foreigners and their children remain detained in the al-Hol displacement camp in northern Syria, having fled the fighting in Baghouz.

Few Western governments have said they will take back their citizens who flocked to territory once controlled by the Islamic State in Iraq and Syria. The group is accused of carrying out horrific atrocities across both countries, including mass executions, sexual slavery and widespread destruction of ancient sites and artifacts.

Last month, Britain stripped London-born teenager Shamima Begum of her British citizenship after she emerged from the caliphate’s final scrap of territory in Baghouz. She is now languishing in a camp in northern Syria, her future uncertain.

Similarly, Parvez was from an affluent neighborhood in West London, where he attended Holland Park School, according to British media reports. He was the first British citizen known to be fighting with the Islamic State in Iraq. He lived both in Raqqa, the group’s de facto capital in Syria, and in Mosul.

In previous posts, he published photos of a ginger kitten he adopted in the caliphate, which he named Anbar, after Iraq’s largest province. At the time, his family expressed shock that he had traveled to Syria to fight for the group.

In the interview Saturday, Parvez claimed to have joined the caliphate to help build the state as a civilian — despite his allegiance to the group’s violent ideology.

He says he worked as a caretaker of mosques under Islamic State control, but soon became disillusioned with the Islamic State’s brutal codes.

“Coming in, you very quickly find out it’s not how it’s [portrayed],” he said of the utopian vision Islamic State members promoted online.

“The things we found out, we found out the hard way,” he said, adding that his superiors forced him and others to fight on the front lines.

The “big fish” of the Islamic State, he said, “stole the money and made their way out a very long time ago.”

He referred to the civilians living in Baghouz, an encampment of tents that made up the Islamic militants’ last stand, as the “crumbs of ISIS,” using a common acronym for the Islamic State.

“There was a complete collapse of social and economic rule. People referred to it as Dar al-Kuffar,” he said, an Arabic term denoting land ruled by nonbelievers.

“There was food, but it was only for the big fish of the Islamic State. I held children in my hands who were dying because there was no food” for the remaining civilians, he said.

He added: “You don’t have to tell me what city I’m in, but can I ask: Is there a McDonald’s here?”