The former chef to Kim Jong-un's father believes that the current supreme leader of North Korea's penchant for sushi and expensive champagne is behind his widely-reported 'weight gain'.

Recently-released photos, which seemed to indicate the dictator's girth has increased, prompted debate around the world. One of CNN's two in-studio experts suggested that Kim's apparent weight gain was a result of there being "nobody there to tell him to say no".

Kenji Fujimoto, who released the memoir I was Kim Jong-il's Cook based on his 13 years in the former leader's service, has finally been able to shed light on what could be behind the expanding waistline of Kim Sr's sucessor.

A recently released photograph of Kim (AFP/Getty) (AFP/Getty Images)

Fujimoto told the Mail Online: "I used to make sushi for the General (Jong-il) at least once a week and Jong-un always joined the dinner. So I could say Jong-un liked sushi."

But it's not all down to raw fish. The chef also said: "He drank a lot. His favourite was Cristal, usually about two bottles [in a sitting]."

Fujimoto also indicated that shark fin soup, a dish which is illegal in the UK, was served during a lavish banquet that he was invited to in 2012.

Cristal, which was referenced so often by rappers such as P.Diddy and Snoop Dogg that the company who produces it moved to distance the brand from hip-hop culture, has a retail price of around £125 per bottle in the UK.

There were concerns over Kim's health last year after the 32-year-old was not seen in public in North Korea for more than a month following reports of ankle surgery.

However, as rumours circulated that the supreme leader was suffering from gout, the country's ambassador to the UK declared that he is healthy.

Since assuming the leadership of North Korea in 2012 Kim has been notable for his ruthless political purges and, in a similar manner to his father, for the feats that he has reportedly achieved.

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Recently, Kim criticised a turtle factory for 'serious shortcomings' after it failed to produce lobsters, a week after he allegedly executed his foreign minister. According to reports, school children in North Korea are to be taught that the supreme leader learned to drive at the age of three.