Puppy fat is nothing other than the fat on the body of a baby or child and which disappears at adolescence.
A study of 8,000 children and teenagers has found almost one in five girls - 17 per cent - aged 12 and 13 have used at least one radical weight control technique.
Fasting was most common, practised by 12 per cent of these girls, followed by vomiting, excessive exercising and chewing but not swallowing food.
But even more concerning, says dietician and health educator Dr Jenny O'Dea, was the sharp rise in girls adopting these habits at 14 and 15, when their bodies were naturally "rounding out."
She said the results, to be presented at an eating disorders conference in Adelaide tomorrow, were proof girls should be taught about puberty and body image from the age of nine, while still at primary school.
"We've got these extremely young girls using these dangerous fad techniques from as young as 12 which is shocking in itself,'' said Dr O'Dea, from the Faculty of Education and Social Work at the University of Sydney.
"Then the numbers doing it shoot up further at 14 once they start to put on that natural layer of body fat normal for all girls in the last stages of puberty.
"They're fighting against this curvaceous shape in the terrible mistaken belief that it's actually normal to have no body fat at all.''
The data was taken from a 2006 national survey and body mass study involving 3,948 boys and 4,267 girls aged five to 19.
Fasting was the most widely practised diet technique for girls aged 12 to 19 but numbers partaking in both billowed at 14 and 15 years old.
Smoking to control weight also increased sharply at this point, and doubled to 13 per cent among girls 16 and over.
Fasting was the only significant issue among boys, affecting five per cent across all age groups.
Dr O'Dea said educators should take heed of the pubertal dieting trend among girls.
"I think we need to be teaching girls to understand their bodies earlier than we currently are, at primary school,'' she said.
"And we need to approach weight control in schools with sensible food and sensible activities, keeping in mind that many children have obviously already used dangerous fad diet methods.''