By correcting a common protein myth, a UK study revealed that one small label made plant-based meals the majority choice.
High meat consumption is one of the most environmentally damaging dietary habits. Livestock farming accounts for roughly 16 % of global greenhouse-gas emissions, takes up 80 % of agricultural land, and drives deforestation, biodiversity loss, water pollution, and the risk of animal-borne diseases.
Yet in efforts to reduce meat intake, one intervention has dominated: carbon labelling.
Dr Chris Macdonald, Director of the Better Protein Institute (BPI), argues that carbon labels — while well-intentioned — often underperform. They’re cognitively demanding, hard to interpret during quick decisions, and rely on complex calculations. Despite these limitations, they remain popular — something Macdonald attributes partly to “environmentalist bias”: prioritising ecological framing over consumer understanding.
The BPI takes a different approach: start by talking to the end user.
In a UK study published in Frontiers in Sustainable Food Systems, Dr Macdonald and his team surveyed over 1,500 consumers and uncovered a key barrier: people believed plant-based meals lacked protein. He called this the “insufficiency illusion” — the mistaken belief that meat-free options fall short nutritionally.
This insight drove a large-scale experiment with over 3,000 participants. Menus were updated with a simple, factual label showing that plant-based options contained comparable protein to meat-based ones.
The results: when protein content was highlighted, meat-free meal selection more than doubled — jumping from under 25 % to over 50 %. The effect held across genders, making the meat-free option the majority choice.
This subtle label is what Macdonald calls a “nudge by proxy” — an indirect cue that shifts behaviour without highlighting the environmental problem. Rather than prescribing what to choose, it provides the specific information people feel they need.
The Business Case: For food operators, this small label delivers measurable results. Since plant-based meals are generally cheaper to produce, every additional sale contributes to higher margins. The change requires no staff training or marketing investment—just a small adjustment to menu design. And by grounding sustainability in evidence rather than ideology, it helps strengthen trust among customers and employees alike.
Do you know of any other nudges that help to promote planet-friendly food?
Feel free to get in touch: hello@green-nudges.com
From Dr Chris Macdonald, a behavioural scientist, author, and founder. Dr Macdonald is a Fellow and Lab Director at Lucy Cavendish College, University of Cambridge; a Fellow at the Institute of Corporate Responsibility and Sustainability; a Supervisor at the University of Cambridge Institute for Sustainability Leadership; and Director of the Better Protein Institute. He was recently named one of the 40 Under 40 in Science and Innovation.
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