In an age of short attention spans and never-ending scrolling, public health professionals may need to reconsider how they combat junk food urges. A new study from Edith Cowan University reveals that when it comes to preventing unhealthy eating, less may be more. 

Researchers have discovered a "15-second sweet spot"—a short, positive health message that appears to be more successful in reducing cravings than longer, standard warnings about obesity and disease. 

The study, directed by Dr Ross Hollett, investigated how different types and lengths of advertising affect adults' initial desires. A total of 505 Australian adults were randomly shown one of two advertisements: one for junk food and one against junk food. They were then asked to indicate their current wants and intentions to eat unhealthy foods. 

Participants were separated into two groups based on Body Mass Index (BMI), a simple formula that uses height and weight to determine whether a person is in the normal range (18.5-25), overweight (25+), or obese (30+). 

“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.” 

Contrary to predictions, a single junk food advertisement did not significantly enhance appetites or consumption intentions, even when participants saw foods they claimed to like. 

However, anti-junk food commercials reduced cravings and the willingness to eat unhealthy meals in both BMI categories. 

The length and tone of the message were essential. 

A 15-second anti-junk commercial outperformed the usual 30-second version among individuals with a normal BMI. “For some viewers, a short, sharp message may have more immediate impact than a longer ad,” Dr Hollett said. 

For participants who were overweight or obese, the message's framing mattered more than its duration. A 15-second advertisement encouraging good eating choices, such as showing appetising, nutritious meals, was more effective than one condemning junk food. 

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

Simply said, positive framing encourages individuals to choose healthier options rather than warning them about the dangers. Instead of just saying "don't eat junk food", the message demonstrates what healthy food looks like and why it may be satisfying. Researchers believe that this strategy decreases psychological resistance and message fatigue. 

The findings are consistent with behavioural science principles. When people are overwhelmed with information, particularly unpleasant or moralising messages, they tend to tune out, a condition known as cognitive overload. Shorter, more focused messages may serve as a mental "circuit breaker", halting urges before they manifest into action. 

“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. 

The repercussions go beyond Australia. With rising obesity rates and relentless junk food promotion on digital platforms, message design may be as important as message substance. Increasing the frequency of brief, positive health messages, particularly on social media, could provide a useful, low-cost approach for reducing unhealthy eating habits. 

For legislators and public health planners, the conclusion is clear: fighting junk food urges may require better, shorter warnings rather than louder ones.