About 90 per cent of Australian teenagers have a mobile phone, but many parents are in the dark about the advertising their kids are being exposed to.

There's increasing concern that corporations are using social media to brainwash youngsters into unhealthy eating patterns that could stay with them for life.

"Teenagers are almost constantly online nowadays. A large part of this time is spent on social media platforms such as Instagram, Snapchat and TikTok," said Ms van der Bend, a Hunter Medical Research Institute researcher.

Ms van der Bend is looking to recruit teenagers aged 13 to 16 for a study - done entirely online - into the food marketing they are exposed to on social media. The study will be done through the University of Newcastle and Wageningen University in The Netherlands, as she plans to compare results between the two countries.

Research has shown that food marketing on television promotes unhealthy food and drink and leads to poorer diets among kids.

"Yet, there's so much we don't know about food marketing on social media. I bet a lot of parents have no idea what their child must be seeing on there all day. That is quite concerning," she said.

Cancer Research UK said in December that young people were "being exposed to junk food adverts across social media, streaming services and by celebrities and influencers".

About 86 per cent of those surveyed saw advertisements for junk food on social media, while 84 per cent also saw them on TV.

Dev Sharma, 15, campaigned on the issue in the UK.

"Whatever industry says, the simple fact is my friends and I don't want to feel bombarded with junk food ads every day," Dev said.

"How can anyone be healthy when our whole digital environment is incredibly skewed and flooded to promote foods that are high in fat, sugar and salt?

"We know there is a direct link between kids seeing ads and childhood obesity and we need action."

Ms van der Bend said millions of adolescents follow brands on social media that sell fast food, snacks and sugary drinks. She said this was alarming because adolescent overweight and obesity rates increased with age and were presently as high as 31 per cent among Australians aged 16 to 17.

"Social media platforms offer food brands a range of new possibilities for more personalised persuasion techniques."

She said this blurred the boundaries between entertainment and advertising.

"Teenagers are highly vulnerable to this type of content, as they are still developing their attitudes and preferences."

Interacting with social media content and sometimes re-creating it "makes them feel like they are part of a group or culture".

"This makes social media very appealing and may even lead to re-advertisement of brands by teenagers themselves," she said.

"On social media, this content is not only coming from celebrities like on TV, but also from friends and peers. This may encourage them to do the same.

"Another thing that makes social media very different from TV is that people can be reached at any place and time, while TV marketing is much more limited to TV-watching hours."

Ms van der Bend said the study would provide insight for strategies to help teens improve their diet quality, promote good mental health and "reduce the risk of cardiovascular disease, type 2 diabetes and some cancers".

She said there may be a case for increased regulations around food marketing to teenagers on social media, "once we get stronger evidence on how it is embedded and the impact it has".

"There are currently no strict regulations for food marketing on social media. Even the restrictions for television and packaging often focus on kids up to 12 years only.

"Children from 13 years old are still developing cognitively as well, and they are highly vulnerable to this type of content."

However, introducing national policy measures would be complex, "as social media is not limited to the regulations of one country".

"Maybe we should approach the social media platforms themselves and aim for stricter rules."

The Global Obesity Centre at Deakin University in Victoria said in a study released in May that "major social media platforms do not have comprehensive policies in place to restrict the marketing of unhealthy foods".

"Globally, existing regulations are proving ineffective in protecting children and adolescents from exposure to the digital marketing of unhealthy foods and beverages," the study concluded.

Associate Professor Gary Sacks said social media platforms should voluntarily adopt junk food advertising restrictions for those under 18, in the same way they had restricted weight loss products, cosmetic procedures and fake news.

Teenagers aged 13 to 16 who are active on social media can join the Newcastle study by emailing daphne.vanderbend@uon.edu.au.