Australian children are exposed to junk food messages for up to three hours a week while playing junior sport, according to a study.
Researchers say children are being bombarded with unprecedented levels of fast food and sugary drink advertising via companies sponsoring community sports clubs.
The research comes after an international report last week revealed that Australia's adult obesity level was growing at one of the fastest rates in the world.
One in four children was also overweight or obese.
The Australian study, published in the Journal of Science and Medicine in Sport, combined information about children's participation in community sport with patterns of food and drink sponsorship of sports clubs.
Children playing outdoor cricket and rugby league were most exposed to unhealthy messages.
Lead author Bridget Kelly, from the University of Wollongong's school of health and society, said her research team was staggered by the magnitude of children's cumulative exposure to these unhealthy messages.
"With nearly two-thirds of all children participating in organised sport regularly, it is deeply concerning to see such a high frequency of fast food and sugary drink sponsorship at local sports clubs undermining the great health benefits of kids' sport," Dr Kelly said.
"Earlier research has already established that kids have high recall and awareness of the sponsors of their own clubs - particularly those featuring sports stars - associating them with positive brand attributes.
"Our study shows that fast food and sugary drink sponsorship of children's sport is pervasive, with opportunities for company branding ranging from signage on uniforms and on field, to vouchers and other promotions."
Dr Kelly said the high rate of children's exposure to unhealthy food and drink marketing was widely recognised as a key contributor to childhood obesity.