A new Edith Cowan University (ECU) study has found advertisements that encourage healthy choices can reduce cravings and intentions to consume unhealthy foods, and in some cases a 15-second message may be more effective than traditional 30-second commercials.

Led by Dr Ross Hollett, the research investigated how the length and framing of junk food and anti-junk food ads influence immediate cravings among adults in different Body Mass Index (BMI) categories.

Anti-junk food ads are public health campaigns designed to discourage people from eating unhealthy foods, either by warning about health risks or promoting healthier choices.

“Junk food advertising in Australia remains largely unregulated, despite significant public health concern,” Dr Hollett said.

“We wanted to understand what actually happens in the moments after adults see junk food and anti-junk food ads.”

The study involved 505 Australian adults who were randomly shown either a junk food or anti-junk food advertisement and then asked to report their immediate cravings and consumption intentions. Responses were analysed in two groups, participants in the normal BMI range (18.5–25) and those classified as overweight (25+) or living with obesity (30+).

Surprisingly, a single junk food advertisement did not significantly increase cravings or intentions to consume junk food, even when participants were shown foods they said they enjoyed.

However, anti-junk food advertisements did reduce cravings and consumption intentions across both BMI groups.

The impact depended on how the message was delivered. For participants in the normal BMI range, a 15-second anti-junk advertisement was more effective than a 30-second version.

“For some viewers, a short, sharp message may have more immediate impact than a longer ad,” Dr Hollett said.

For participants classified as overweight or living with obesity, a 15-second advertisement encouraging healthy food choices was more effective than one criticising junk food.

“This suggests positively framed health messages may resonate more strongly with audiences carrying greater health risks,” Dr Hollett said.

“If we’re investing in public health campaigns, it’s important to know not just whether they work, but for whom and under what conditions.”

Dr Hollett said increasing the frequency of brief, positively framed health messages could help reduce the public health risks associated with junk food consumption.

The study ‘Length and framing of anti-junk food ads impact inclinations to consume junk food among normal weight, overweight, and adults with obesity’ was published in the Health Promotion Journal of Australia.