Caden Benjamin, from Standerton in South Africa, weighs over 14 stone because of his constant overeating.
He has been diagnosed with Prader-Willi syndrome, defined by an obsessive compulsion to eat.
His mother Zola Benjamin said: ‘At one point, Caden was eating toilet paper. He’d eat rolls of it.
Caden underwent a tracheotomy several years ago and now breathes through a tube inserted into his windpipe.
At three years old Caden weighed six stone, but his mother did not know what was wrong with him.
Eventually, a doctor in Pretoria, Gauteng Province, pinpointed his illness.
Prader-Willi affects thousands of people worldwide and also causes restricted growth and reduced muscle tone.
Sufferers often cannot consume more food than their peers because their bodies burn fewer calories.
Ms Benjamin said: ‘Normally he would start off the day by eating four slices of cheese toast and then an hour later he would drink Coke and eat leftover food from the night before.
‘Then at lunch he’d eat two large pieces of chicken. He’d eat hourly for the rest of the day.’
Ms Benjamin has now had to lock all her kitchen cabinets and her fridge, and hide all her the food in her house.
Caden struggles to move around and even breathe because he is so overweight.
He also suffers from bouts of depression because he is unable to live like a normal child.
His mother added: ‘Sometimes he’ll just break down in tears and tells me he wants to go and play with the other children outside.
‘But he is unable to do that and there’s no way I can help him.’