"Every hour kids spend online increases chance of buying junk food by a fifth," reports The Daily Telegraph.
A Cancer Research UK survey of almost 2,500 children found those who used the internet or watched commercial television for more than half an hour a day were more likely to ask for, buy or eat junk food (food high in fat, salt and sugar).
Previous studies of children's junk food consumption and advertising have mainly looked at their television watching habits.
The studies fed into a set of guidelines produced in 2008 by the broadcaster regulator, Ofcom, that prohibit junk food advertising from appearing alongside children's television.
But the authors of the report argue that in the age of streaming and on-demand media and social networks, these guidelines may now need to be updated.
Researchers found the primary school-age children surveyed spent an average of 16 hours a week on the internet.
They found 4 of the 5 most popular websites the children used were commercial sites that display online advertising.
That compares to an average of 22 hours of television a week, 12 hours of which was on commercial channels that show adverts.
There are currently no UK guidelines on screen time for children. These are expected in 2019.
Canadian guidelines recommend that screen time for children (including TV, smartphones, tablets and video games) should be restricted to less than 2 hours a day.
The study was carried out by researchers from the University of Liverpool and the charity Cancer Research UK.
In an online survey, the researchers asked 2,471 children aged 7 to 11, plus 1 parent per child, about:
Researchers also calculated the likely deprivation level of the family using their postcode.
Researchers found links between the amount of time children spent watching TV or on the internet and their likelihood of being overweight, asking for junk food, and buying and eating certain types of junk food.
Time spent watching commercial TV or online wasn't linked to children's activity levels.
Each additional hour children spent watching commercial TV was linked to:
Each additional hour children spent online was linked to:
Children who watched more than 3 hours of commercial TV a day were 59% more likely to be overweight or obese than children who watched half an hour a day or less.
Those who used the internet more than 3 hours a day were 79% more likely to be overweight or obese than children who used the internet half an hour a day or less.
The study results suggest that watching commercial TV or using internet sites with advertising may be linked to children's desire for high-sugar, high-fat and high-salt foods they see advertised.
Cancer Research UK has called for the government to ban junk food advertising altogether on TV before 9pm and bring in similar protection for children exposed to advertising online.
Parents wanting to avoid "pester power" might want to think about restricting the amount of time their children spend online, as well as watching commercial TV.
But it's important to note that we don't know whether these results mean TV or internet use directly causes obesity or increased junk food consumption.
Obesity and diet are complicated, and many different factors are likely to be involved. For example, parents have a big influence on children's diets, as well as on how much TV and internet use they're allowed.
There are some limitations to online surveys. Though the researchers tried to get a broad sample representative of the population, there may still have been selection bias, as parents and children who frequently use the internet are more likely to have participated.
The results are also reliant on people accurately recalling the amount of time spent on each activity, and children may have been reluctant to divulge their true onscreen time or consumption of unhealthy foods.
We also need to be cautious about the report, as the full results aren't easily accessible and haven't been published in a peer-reviewed journal. That means they haven't been subjected to the scrutiny other published research undergoes.
That said, there have been a number of peer-reviewed studies we have covered in recent years that suggest a link between excessive screen time and adverse health outcomes in children, including obesity, diabetes and high blood pressure.