Primary Schoolwear in Sydney stocks boys' shirts in size 30, which fits a 122-centimetre chest and a 47-centimetre neck. Girls' clothes go up to size 26.
The company, which makes clothing for public and private schools around Australia, has had more demand than ever for larger-sized clothing, forcing it to expand its scale to XXXXXL.
Clothing of that size measures 110 centimetres around the waist, 46 centimetres more than the smallest size, XXXS, which is made to fit the average 10-year-old.
Jenni Mackillop from the company's NSW branch said parents often asked for specially made clothing to fit larger children. "We do see our fair share of little chubbies," Ms Mackillop said.
Preproduction manager Jo Kellock said the company had noticed a growth of up to five centimetres in waist measurements in the past two years alone.
National studies had shown that children had grown about two centimetres in height, on average.
Ms Kellock said designs had to be "straightened out" at the waist, where previously they were nipped in, to cater for the increasingly common "pear shape" among schoolchildren.
National studies have confirmed the popular belief that children are also growing taller.
At the other end of the spectrum, manufacturers have had to make tinier sizes for Asian migrant children who are often far smaller than their Western school chums.
Nutritionist Rosemary Stanton said that while studies had shown NSW children were playing more sport, they were still getting fatter.
"They may burn up 300 calories and then eat 400 calories," Dr Stanton said. "Children are thinking they are abnormal if they do not have junk food every day. There isn't any mystery. We know kids are eating more."
Children were walking to school less often because it was not considered safe. Junk food had become the norm because of the sheer amount of snack foods that were readily available, Dr Stanton said.
"The kids are the victims here," she said. "We've got to take child obesity seriously, but overwhelmingly it is society's problem."
Children who were very overweight faced psychological and social problems and were at greater risk of type 2 diabetes, sleep apnoea, asthma and heart disease later in life.
Dr Stanton urged Australian supermarkets to use a labelling system to advise people how often a certain type of food should be eaten.
Source: The Sun-Herald