The increase in childhood obesity is being caused by addiction to "toxic", sugar-filled manufactured foods, a US researcher has claimed.
A small quantity - but a lot of calories
Robert Lustig, a University of California San Francisco child health expert said high-sugar, low-fibre diets cause hormone imbalances.
These then mean children overeat, he said in Nature Clinical Practice Endocrinology & Metabolism.
The number of overweight and obese children is rising in the US and UK.
One in four children in England are obese, official statistics published earlier this year showed.
And 'adult' diseases, such as type 2 diabetes, are being seen in children.
Professor Lustig said food manufacturing practices have created a "toxic environment" that "doomed" children to being overweight.
He added too much fructose [fruit sugar] and too little fibre in foods both act to boost insulin levels.
Insulin acts on the brain to encourage eating by blocking signals that travel from the body's fat stores to the brain and by stimulating a pleasurable dopamine "rush" after eating.
Professor Lustig said food processing had changed over the last 30 years, with sugar being added to a wide variety of foods that never used to have it, and fibre being removed from many foods to create "essentially addictive" foods.
He said children could not be blamed for eating badly when they were offered such unhealthy options.
"The concept of personal responsibility is not tenable in children. No child chooses to be obese," he added.
"Young children are not responsible for food choices at home or at school, and it can hardly be said that pre-school children, in whom obesity is rampant, are in a position to accept personal responsibility."
"If we don't fix this, our children will continue to lose."
Catherine Collins, of the British Dietetic Association, said: "The energy density of today's diet means its relatively easy to eat a high calorie diet with what looks a very modest quantity of food on your plate.
"For example, a 50g bar of chocolate contains around 270kcal (calories) so has an 'energy density' of 5.4kcal a gram. But a 150g banana would provide around 140kcal.
"But I am not sure I consider the individual child/parent 'blameless'.
"Children tend to have a higher energy need per kilogram of body weight than adults, which does translate into a healthy appetite.
"And while children are not 'masters of their own destiny' as Lustig suggests, they do control their intake to some extent such as through pocket money."
She added: "We have to encourage children to choose non-food preferences to spend their money on, or to 'benchmark' their own diet against a healthy standard."