Children talk about nutrition and health at school, and something different about traveling home, the Cancer Council has revealed.
The new study revealed that 82 percent of Sydney's food barges and rail junk food stations, despite rising childhood obesity rates.
"This is extremely alarming because 21.4 percent of NSWs in the age of 5 to 16 are now overweight or obese," said Wendy Watson, NSW Nutrition Program Manager.
"If you carry that weight at an adult age that puts them at risk of 12 different types of cancer, as well as heart disease and Type 2 diabetes."
NSW's government has several initiatives to educate children about healthy diets from pre-school age to adulthood.
Public transport ads are in opposition to this message, and the target audience is too often children.
Every month, children under 15 in NSW make up more than 3.3 million bus trips and more than 2 million journeys by train.
"Only 12 percent of the food that children see when they came out and whether they are healthy foods has undermined parents' efforts to create healthy habits."
The Cancer Council NSW wants the government to remove the advertising of unwanted foods from public transport.
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It's not without precedent.
The ACT government has done so on buses, and in Western Australia alcohol advertising is forbidden on all public transport.
"Wealthy obesity is the prime priority of the premier. If we want to see a real fall in overweight and obesity, this is one way NSW governments can show leadership," said Mrs. Watson.