Ten-year-old Ben Green has a rare condition called Prader-Willi syndrome (PWS) which stops him realising when his stomach is full.
The condition affects just one in 22,000 people and leaves Ben with crippling hunger pangs, making him constantly ravenous and wanting to eat.
The condition means he will eat anything he sees, including cat food and toothpaste if left alone. His parents, Paul and Angela, have to watch their son 24 hours a day to stop him binge eating, but denying Ben his food can led to exhausting tantrums that can last for hours.
'We have to supervise Ben's every move. Left unattended, he would eat absolutely anything,' explains mum, Angela.
His compulsion takes over every other emotion. We have to say no and that's when the crying starts. He can go on and on for ages. He sobs in my arms. It's horrendous. I have to be as strong as I can because I know I have to help him.
Ben has to stick to a calorie-controlled diet to keep his condition under control, and unless his eating is monitored, he could become so overweight it could kill him.
The little lad is already overweight, which is partly a symptom of PWS and partly down to a curvature of the spine which restricts him to a wheelchair, which limits the amount of calories he can burn off.
Ben's dad, Paul, says they thought something might be wrong right from Ben's birth:
'He was three weeks premature and at first we thought that might be why he was quiet but then our anxieties grew. We weren't new parents. We knew something was wrong. Initially, babies with PWS are so weak and find it difficult to feed. Then they start to grow up and begin to develop a voracious appetite.
Now we have to watch Ben constantly. He'll open cupboards, looking for food. At a friend's house I spotted him eyeing up the bowl of cat food on the floor. I think he'd probably tried a bit before I managed to get him away. If he sees anyone with food or drink, he will use his considerable charm to wheedle something out of people.
Ben's condition means simple family days out can be tricky.
'We were at the allotment working on the garden and we let Ben have an ice lolly - which was a very rare and infrequent treat,' explains Angela.
'Without me knowing, a wasp must have got itself stuck on the lolly and Ben put the insect in his mouth. It stung him but that didn't cause Ben to hit the roof. The fact that we had to throw the lolly away was what made him go wild. We tried to explain that the lolly was ruined because the wasp was stuck on it but he wasn't bothered.
'In the end, we had to bring him home from the allotment because he was getting all distressed.'
Neither Paul or Angela are able to work as they need to be at home to look after Ben, but despite the battles the families face everyday, Angela says they wouldn't swap their son for anything:
'He can be so happy and carefree. He has a heart-melting smile and he loves to talk to new people. He can hold a very grown-up conversation.'