Parents have long encouraged children to finish everything on their plates, not least because of guilt about wasting food.
But new research suggests this tactic could be fuelling the obesity epidemic.
Ever-growing portion sizes mean children are being pressurised into eating more than they need which, experts say, means they don't know when to stop.
Katie Loth, a dietician at the University of Minnesota in Minneapolis, U.S., told HealthDay: ‘I was surprised at some of the parent behaviours, like feeling that their children should clean their plates and not waste food.
‘In the 1950s, cleaning your plate meant something different.
'Portion sizes have got bigger over time, and if you encourage kids to rely on environmental indicators, like how much food is on their plates or the time of day, they'll lose the ability to rely on internal cues to know whether they're hungry or full.’
Ms Loth studied data about 2,200 teenagers and 3,500 parents.
She found that fathers were more likely to pressurise their children into eating all of their food than mothers were.
She also discovered that teenage boys were more likely to be put under pressure to finish their food than teenage girls.
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Dr Michael Hobaugh, chief of medical staff at La Rabida Children’s Hospital in Chicago, believes that childhood obesity is being exacerbated by parents who are unable to judge whether their child is the right weight.
He told the website: ‘There's now so much obesity in the United States that when we see a child who is normal weight, inevitably, a parent will think the child is too skinny.
‘But if a pediatrician charts that child's height and weight, he or she may even be overweight.
‘There's a wide range of normal, and for many teens it's normal to be slender and gangly.’
Children are growing up unable to tell when they have had enough to eat
The research comes just days after Dr Brian Wansink, of Cornell University, in New York, suggested that the key to avoiding over-eating at all-you-can-eat buffets is to take a smaller plate.
Dr Wansink observed the behaviour of slim people at buffets and compared it to the behaviour of larger people.
He noticed that thin people were seven times more likely to take a small plate and that the thinner diners tended to look at all of the food on offer before choosing what to have.
By contrast, larger diners tended to consider each item individually.
He told HealthDay: ‘Skinny people are more likely to scout out the food. They're more likely to look at the different alternatives before they pounce on something.
‘Heavy people just tend to pick up a plate and look at each item and say, “Do I want it? Yes or no”.’