In the Netherlands, ‘just-in-time’ digital nudges encouraged healthier online food choices by aligning with users’ preferences.
What unsustainable behaviour needs to change:
With more of us buying groceries online, a quiet shift is underway in how food decisions are made. But as digital convenience grows, so too does the visibility of unhealthy options—often placed front and centre as popular suggestions. Since many food decisions are quick and habitual, we become susceptible to these influences.
This makes digital platforms a key opportunity for smarter and more precise interventions. Nudges can be delivered ‘just-in-time’ – exactly when someone selects an unhealthy item, offering healthier swaps at the moment it matters most. Even more promising: unlike the conventional ‘one-size-fits-all approach’ in physical stores, these digital nudges can be personalised—both in what content they recommend (“healthier” vs. “cheaper” product alternative) and how they format these recommendations (image vs. text)—to match the user’s food preferences and thinking style.
The question is, does that make them more effective?
The Green Nudge:
The researchers tested whether personalised ‘just-in-time’ (JIT) nudges could help online shoppers make healthier food choices. In a controlled lab study, 200 participants completed a grocery task using a mock supermarket app.
They were placed into one of five groups:
Control – No nudges
Non-personalised – Nudges mismatched on both content and type
Content personalised only – Nudges matched to users’ food preferences (health vs. price)
Type personalised only – Nudges matched to users’ thinking styles and preferred format (image vs. text)
Fully personalised – Nudges matched on both content and type
Nudges recommended healthier alternatives just-in-time, when someone initially added an unhealthy item (e.g., Coca-Cola Regular) to their virtual shopping basket.
The results: Personalising nudge type made an immediate difference: Image-based nudges for visual thinkers, or text-based nudges for verbal ones, were 7% more effective in helping users accept healthier product recommendations. Personalising nudge content showed more subtle and delayed effects: when aligned with the user’s food preferences, nudges led to a small increase in healthier basket replacements (+0.8%) prior to checkout. When misaligned, they backfired slightly (-2.3%).
All four groups that received ‘just-in-time’ nudges outperformed the control group without nudges in terms of greater healthier purchases at checkout and user satisfaction. The takeaway: even small, well-timed nudges—tailored to how people think and what they care about—can make digital food environments more supportive of healthy, sustainable choices.
Do you know any digital nudges that help people make healthier or more sustainable food choices ? Get in touch: hello@green-nudges.com
From Rachelle de Vries, Consumer Scientist at the Unilever Foods Innovation Centre, and Nynke van der Laan Associate professor Digital Health Communication at Tilburg University. This research was part of a Health~Holland-funded collaboration between Tilburg University and the mobile app developer Nakko. Together, the team explored how personalised, ‘just-in-time’ nudges can empower healthier food choices in digital environments.
