Robbie Williams is on a strict clean-eating diet during the day because his rare sleep-eating disorder means he gets up in the middle of the night and scoffs ''loads of sugar''.

The 'Candy' hitmaker revealed last year that he suffers with Nocturnal Sleep-related Eating Disorder [NS-RED] and, in a bid to counteract the damage he does when he's rummaging through the cupboards in the early hours of the morning, he's only allowed to eat ''sad'' salads and protein when he's awake.

Speaking in his new video blog entitled 'Vloggie Williams', Robbie said: ''I'm doing this very weird thing, and it's been for over a year now, where I night-eat. 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 and leaves me not a lot of room for [eating] bad stuff during the day because bad stuff happens at night, when I am asleep. It's just weird, but it's what's happening. So there's zero sad, shameful secret treats because I have my treat in the middle of the night when I don't even know about it.''

And considering he spends most of the night stuffing his face with calorific treats, it's no wonder the 43-year-old singer snaps at his wife Ayda Field, with whom he has kids Theodora, four, and Charlton, two, when she tries to wake him up in the morning.

He explained: ''I'm crap when I've just woke up. Ayda my wife is like: '[makes jumbled sentence sound]' and I'm like: 'Just shut up, I need a coffee!'''