Eye doctors in Bristol cared for the young man after his vision had deteriorated to the point of blindness.
Since leaving primary school, the teen had been eating only French fries, Pringles and white bread, as well as an occasional slice of ham or a sausage.
Tests revealed he had severe vitamin deficiencies and malnutrition damage.
In recent groundbreaking research, it was found that children under the age of two in Nepal are also getting a quarter of their calories from junk food and warned their diet is linked to stunting and undernutrition.
However, in Nepal children are more dependent on biscuits, crisps, instant noodles and sugary drinks. These foods are apparently replacing foods with the vitamins, minerals and other vital nutrients babies need to grow well, say the researchers.
The work, published in the Journal of Nutrition, illustrates that the 21st-century junk food diet spreading around the globe is linked not just to obesity but also to poor growth in children and life-changing health problems like atopic disorders, poor academics, constipation, addiction, less energy, depression, sleep disturbance and more recently blindness.
Extreme picky eater
The adolescent, who cannot be named, had seen his GP at the age of 14 because he had been feeling tired and unwell. At that time he was diagnosed with vitamin B12 deficiency and put on supplements, but he did not stick with the treatment or improve his poor diet.
Three years later, he was taken to the Bristol Eye Hospital because of progressive sight loss, Annals of Internal Medicine journal reports.
Shocking findings
He was not over or underweight, but was severely malnourished.
He had lost minerals from his bone, which was really quite shocking for a boy of his age.
In terms of his sight loss, he met the criteria for being registered blind.
Nutritional optic neuropathy - the condition the young man has - is treatable if diagnosed early. Left too long, however, the nerve fibres in the optic nerve die and the damage becomes permanent.
Cases like this are uncommon, but the parents should be aware of the potential harm that can be caused by picky eating, and seek expert help.
