The report, based on a YouGov survey, involved 3,348 young people (aged 11-19) in the UK being questioned on their TV viewing habits and diet.
When teens watched TV without adverts, researchers found no link between screen time and likelihood of eating more junk food.
They concluded that this suggests the adverts on commercial TV may be driving youngsters to snack on more unhealthy food.
“This is the strongest evidence yet that junk food adverts could increase how much teens choose to eat,” said the study’s lead author Dr Jyotsna Vohra.
“We’re not claiming that every teenager who watches commercial TV will gorge on junk food, but this research suggests there is a strong association between advertisements and eating habits.”
Dr Vohra said it has been 10 years since the first TV junk food marketing regulations were introduced by Ofcom and they’re “seriously out of date”.
“Ofcom must stop junk food adverts being shown during programmes that are popular with young people, such as talent shows and football matches, where there’s currently no regulation,” she said.
“Our report suggests that reducing junk food TV marketing could help to halt the obesity crisis.”
The report, said to be the “biggest ever UK study” to assess the association between TV viewing and diet, found that teens who said they regularly streamed TV shows with ads were more than twice as likely (139%) to drink fizzy drinks than someone with low exposure to TV adverts.
This may have long-lasting ramifications as Professor Linda Bauld, Cancer Research UK’s prevention expert, said: “Obese children are five times more likely to remain obese as adults which can increase their risk of cancer later in life.
“The food industry will continue to push their products into the minds of teens if they’re allowed to do so.
“The Government needs to work with Ofcom to protect the health of the next generation.”
Responding to the report, Professor Russell Viner, officer for health promotion for the Royal College of Paediatrics and Child Health (RCPCH), said the impact of junk food marketing on young people’s health is something the RCPCH, as well as a number of other health organisations, have long been warning about.
“This research appears to be the biggest UK study of its kind and shows the power of advertising and the true impact it has on young people’s waistlines,” he said.
“Companies claim that advertising merely affects what brands children and young people chose - but the evidence is growing that advertising increases the amount our children consume.
“We urge the Government to show it is serious about protecting children’s health by banning junk food advertising before the 9pm watershed. Only then can children reclaim their childhood.”