The boy identified as Caden Benjamin, from Standerton in South Africa, weighs 14 stone 2lbs (90 kilogrammes) because of his constant overeating.
Now, he has been diagnosed with genetic disorder called Prader-Willi syndrome, which is characterised by an obsessive compulsion to eat. His mother Zola Benjamin says it means Caden will eat anything he can get his hands on.
'At one point, Caden was eating toilet paper. He'd eat rolls of it,' she said.
'Actually, he'd eat any paper he would find in the house. If there's nothing for him to eat, he'll scrape together the dirt he finds on the floor and eat that.'
Several years ago, he was forced to undergo a tracheotomy and he now breathes through a tube inserted into his windpipe.
Prader-Willi syndrome is a rare, incurable disorder that affects thousands of people worldwide, resulting in physical, mental and behavioural problems.
The condition is made worse by the fact that people need less food than their peers because their bodies have less muscle and tend to burn fewer calories.
Ms Benjamin added: 'At three years old he was 40 kg (6 stone 4 lbs) and at that time, we didn't know what was wrong with him.
'We went to a number of doctors and no one could tell us what was wrong and why he was gaining so much weight.'
Eventually, a doctor at the Steve Biko Academic Hospital in Pretoria ran further tests and diagnosed Caden's illness.
Now, Caden struggles to move around and even breathe because he is so overweight.
He also suffers bouts of depression because he is unable to live like a normal child.
'Sometimes he'll just break down in tears and tells me he wants to go and play with the other children outside,' said Ms Benjamin.
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