Like thousands of Australian teenagers, Tom and Ellie Bryant enjoy scrolling through videos on social media platform TikTok.
The 13-year-old twins from Melbourne's outer east are really into Formula 1 videos right now.
Some of their other friends enjoy the amusing viral dances and "challenges" that have made TikTok famous.
TikTok says it has more than 7 million users in Australia, so it is little wonder big brands have sought to cash in on an emerging market.
However, researchers say major junk food companies are targeting children under 18 on TikTok and using "insidious" advertising tactics.
Pepsi 'challenge' lauded as 'TikTok at its best'
A study released today by Deakin University looked at the behaviour of 16 international food and beverage brands on TikTok.
Through the analysis of more than 500 videos, the researchers said businesses were trying to lure young social media users into becoming unofficial ambassadors, often through "challenges" involving products.
In one global campaign viewed billions of times, soccer stars Lionel Messi and Paul Pogba kicked balls around and tossed Pepsi cans to each other, encouraging TikTok users to create similar videos.
On its website, the social media company trumpeted the advertising campaign as "TikTok at its best" and said it attracted "hundreds of thousands of young people".
In another, American TikTok users were encouraged to learn a dance, perform it at a Burger King restaurant, and share it online to receive a $1 burger.
In Australia, influencers were paid by McDonald's to encourage TikTokers to re-create the "Maccas jingle" to mark the restaurant's 50th anniversary in the country.
Deakin University associate professor Kathryn Backholer described the branded campaigns as "an incredibly insidious strategy by TikTok and junk food marketing companies".
Her research colleague Ruby Brooks said one in four Australian kids used TikTok.
"The junk food companies are getting a whole lot of free marketing for products that we know are harmful to children's health, while the kids or other users producing this marketing receive little to no benefit in return," Dr Brooks said.
"We'd like to see strong government action that puts kids' health ahead of food industry profits and restricts kids' exposure to unhealthy food and beverage marketing."
In a statement, a TikTok spokesperson said the company had clear advertising policies to help keep its community safe.
"Our policies explicitly state that ads for HFSS foods [foods high in fat, salt or sugar] should not feature a specific call to purchase and should not be aimed at users aged 16 years and under," the spokesperson said.
Lots of teens 'just scroll past it'
But can kids see through the spin? Many certainly can.
Ellie and Tom Bryant say they usually ignore social media campaigns that try to sell products.
"A lot of people I know just scroll past and don't think about it, but there are definitely some people that will buy it and try it," Ellie said.
Figures from the Australian Bureau of Statistics show 67 per cent of adults were struggling with excess weight in 2018.
If the trend continues, 18 million adults could be overweight or obese by 2030.
Public health advocates have long called for junk food ads to be banned on commercial television during children's viewing hours.
The Greens have been pushing for the measure for at least 15 years.
The National Obesity Strategy, backed by the former federal government earlier this year, outlined a crackdown on junk food advertising as one step towards reducing childhood obesity.
However, social media platforms like TikTok present an even tougher regulatory challenge than traditional media, with food and drink ads nine times more common online than on television, according to a study published in the Journal of Medical Internet Research last year.
Dr Brooks called on the Australian government to follow the UK, which is moving to ban junk food advertising online.
Labor's federal Health Minister Mark Butler was contacted for comment.
