“I’m doing this weird thing, it’s very weird and it’s been over a year now, where I night-eat,” the singer said on his new vlog, Vloggie.
“I am absolutely asleep and I get up and I go and eat. I don’t do it on purpose, I’m not aware I’m doing it, but it happens.
“And apparently in my sleep I don’t want kale. I want sugar - and loads of it.
“It’s been super weird, as you can imagine, so that leaves me not a lot of room for [eating] bad stuff during the day because bad stuff happens while I’m asleep.”
According to Dr Clare Morrison, GP at online doctor and pharmacy MedExpress, the condition Williams is describing is called nocturnal sleep-related eating disorder – or NS-RED - but what is the condition and can it be cured?
Dr Morrison explained that NS-RED is a rare condition that affects just 1-3% of the general population.
“However, 10-15% of people with eating disorders are affected,” she told HuffPost UK.
“Most people who suffer from NS-RED are highly anxious individuals, with many of them dieting during the day, leaving them very hungry at night, when their control is weak.”
While it’s not entirely clear what causes people to eat during their sleep, Dr Morrison said that sufferers sometimes have histories of drug abuse, alcoholism and sleep disorders.
“They often suffer from fragmented sleep patterns. NS-RED could also have a genetic component,” she added.
Williams joked that he often reaches for sugary treats during the night, meaning that he no longer eats unhealthy food during the day because “I have my treat in the middle of the night when I don’t even know about it”.
Dr Morrison said eating these kinds of foods is not uncommon for NS-RED sufferers.
“On reading about Robbie Williams’ experience, it’s not surprising that his side effects include weight gain. This aspect of the disorder is very frustrating for people who are trying to lose weight,” she said.
“The food sought out by sufferers tends to be high in sugar and fat - foods dieters would likely to avoid during the day.”
She added that NS-RED can also lead to depression and heightened anxiety, due to the lack of control sufferers feel.
“Often people feel they are going mad and sometimes they are accused of exaggerating or imagining things, which doesn’t help,” she said.
For anyone who believes they may be suffering from NS-RED, Dr Morrison recommends seeking help at a sleep disorders treatment centre.
“Brain activity will be monitored and intervention taken to reduce stress and anxiety, such as stress management classes and counselling,” she explained.
“Avoid sleeping pills – they can increase confusion.”