Healthy proportions: animal-sourced food and the plant-based shift

By Professor Dame Theresa Marteau, Fellow of the El-Erian Institute of Behavioural Economics and Policy

By changing diets we could prevent around 15 million premature deaths each year, cut billions of tonnes of emissions and halt biodiversity loss. How?

By shifting away from animal-sourced, highly processed foods towards eating mainly plant-based, minimally processed ones, accessible to everyone.

If we also used sustainable and ecological intensification practices to produce our mainly plant-based food, alongside cutting food loss and waste, we could halve the 30% of greenhouse gas emissions our global food system currently generates.

And there’s even more to be gained. These sizeable wins would deliver returns of $5 trillion a year from investments of around one tenth of that sum from better health, climate resilience and restored ecosystems.

These are the headlines from the latest EAT-Lancet report published on 2 October 2025.

The question this answered was: how we can feed 9.6 billion people, the expected number living on our planet by 2050, a healthy diet, produced within planetary boundaries?

I was invited to contribute my expertise in changing behaviour across populations. I worked alongside 23 other Commissioners from 6 different continents on this update of the 2019 report. These experts included environmental scientists, nutrition experts, food systems advisors and justice scholars. It was inspiring and often daunting as we realised the scale of our ambition.

Two questions I’m often asked about this work are first, what is the Planetary Health Diet and second, how can everyone access it?  

Common misconceptions about the Planetary Health Diet

The Planetary Health Diet is not a single diet that everyone should be eating. We are not supposed to eat the same food. It is flexible. It can be adapted to be flexitarian, pescatarian, vegetarian or vegan. It can and should be adapted to local food cultures and tastes. The scale and type of adaptation depend on existing eating patterns (see figure 2 from the report below). Take red meat. Globally, we need to reduce consumption by around 33%. But some of us more than others. US and Canadian adults eat 7 times the optimum amount of red meat, with Europe around 6 times and the Middle East and North African twice the recommended amount.

Human health was our top consideration

The second common misconception is that the Planetary Health Diet is designed to be environmentally sustainable. While cutting animal-based foods will certainly protect our planet’s biodiversity and its climate, the first consideration in designing the diet was optimising human health. The Planetary adjective comes from how the food is produced, reducing its damaging impact on the 9 planetary boundaries on which all of life depends. The safe operating space for 6 of these has already been breached – the current food system is the culprit for 5 out of these 6 transgressions. Chief amongst the causes are greenhouse gas emissions from livestock, deforestation, cropland expansion, habitat loss, nitrogen, phosphorous, pesticides, plastics and other chemical pollutants.

The proportions of a Planetary Diet

At its core we designed a diet that is rich in plant-based foods and minimally processed. It includes legumes – peas, beans and lentils, whole grains, vegetables, fruits, nuts and seeds. It also includes fish, dairy and some meat. Looking at protein sources, we can see how the Planetary Health Diet diverges from our western diets. While one portion of protein-rich legumes is recommended each day in the Planetary Health Diet, a maximum of one portion of red meat is recommended per week.

The Planetary Health Diet has a strong inverse relationship with developing obesity, type 2 diabetes, heart disease, stroke, colorectal and lung cancers. It would help avoid millions of premature deaths each year.

How can we make this diet accessible and appealing to everyone?

Around one in 3 people cannot afford a healthy diet and, despite there being enough food for everyone, around one billion people remain undernourished and one billion people are malnourished in living with obesity.

Policy packages need to increase the affordability and appeal of the Planetary Health Diet.

We can increase the affordability of this diet for everyone using taxes and shifting subsidies away from unsustainable practices including animal agriculture. We also need to increase the purchasing power of the poorest 20 % of households, using social protection measures.

By adopting mandatory health warnings of the kind being used to good effect in Chile and other parts of South America, together with restricting advertising of health-harming highly processed foods, the appeal of unhealthy foods falls along with their consumption.

Insufficient political leadership and the abuse of corporate power to maintain the status quo are 2 key barriers to transitioning our global food system that we need to address. The publication of the 75-page EAT Lancet Report in October 2025 is just the start.

The Commission is now engaging leaders in cities and nations across the world to share our vision for a healthy, sustainable and just food system and how they can help achieve this.

We all have a part to play.

I look at my shopping basket, college cafeterias, local schools, the food court of our teaching hospital and ask – how well-aligned to the Planetary Health Diet is the food on offer?

By asking a few focused questions of those designing the food environments you interact with and offering some support and guidance, you too can become part of the global team working to transform our unhealthy, unsustainable and unjust food system to one that allows all of us and our planet to thrive.