Most parents don't think their overweight children are fat - and heavy parents are the worst judges of them all, a study has found.
A survey of more than 1,200 Melbourne families has revealed the majority of caregivers believe their kids are of normal weight when they are overweight or even obese.
Parents of 5 to 6-year-olds were the worst, with 90 per cent wrongly judging their overweight child.
And 63 per cent of parents of overweight 10 to 12-year-olds made the same mistake.
Deakin University researcher David Crawford said the findings, published in the journal Public Health Nutrition, were alarming given Australia was in the grip of an obesity epidemic.
"These are quite troubling results and suggest that current obesity prevention campaigns are not hitting the mark with parents," said Prof Crawford, head of the Centre for Physical Activity and Nutrition Research.
"Parents are part of the front line in the battle to reverse the trend of obesity in children.
"It is therefore essential that they are armed with information and practical strategies that they understand and can easily build into their daily lives."
He said the results were not surprising because waistlines were expanding across the whole population, making obesity harder to recognise.
"Almost one in two people are overweight now ... so it's almost more usual than unusual," Prof Crawford said.
Children are also growing quickly, making it hard to judge weight, and many parents also believe their child will grow out of it which, research shows, is not the case.
Mothers in particular tended to judge a weight problem on whether their child was teased at school - a poor marker of overweight.
Interestingly, it was the overweight adults that were least likely to recognise their child's weight problem, probably because they don't recognise it in themselves, Prof Crawford said.
Despite not recognising the problem, most parents said they took care to promote a balanced diet and physical activity and cut back on junk food in the home.
But few parents boosted fruit and vegetables intake, limited television viewing or stopped children drinking high energy drinks to control weight.
Parents need to follow the pyramid below and encourage (insist!) that their kids do the same.