Unhealthy diets tend to be bad for the planet, study reveals

Cutting out your morning pastry and expensive coffee might help fight the climate crisis, a University of Leeds-led study published today reveals.

Many less nutritious foods and drink account for nearly a quarter of diet-related greenhouse gas emissions, the research team found, after studying more than 3000 generic foods and 40,000 branded items.

The study confirms that unhealthy diets also tend to be bad for the planet. Sweets, cakes and biscuits account for 8.5% of food-related greenhouse gasses. Drinks such as tea, coffee and alcohol contribute15.1% – a combined total of23.6%.

Previous studies that have identified foods with a high environmental impact have used very broad food groups and tied them to crude estimates of greenhouse gas emissions. This meant that while they were useful for highlighting actions that could be taken at a national or population level, they provided only limited guidance for individuals and families seeking to limit the climate impact of their lifestyle.

The work of the Leeds-led team, published in scientific journal PLOS ONE, provides a far more detailed picture of the impact of a  person's diet – and the changes each of us can make in our eating habits to combat climate change,  while improving our nutrient intake.

We all want to do our bit to help save the planet and the decisions we make can contribute to that cause. It's true that we do need big cultural changes – such as significantly reducing our consumption of meat and dairy products which together contribute around 46%of our diet-related emissions.

However, our work shows that small changes can also produce big gains. You can live a more environmentally sustainable life by just cutting out sweets and drinking less coffee."

Dr Holly Rippin, lead author, post-doctoral researcher, University of Leeds School of Medicine

Professor Janet Cade from the University's School of Food Science and Nutrition, said: "Obesity-related disease and disability are big problems in most Western countries. This detailed study confirms that diets that are better for the planet's health are better for our own personal health too. It also raises more issues around the labelling of food as different brands of the same product vary in their environmental impact."

Non-vegetarian diets produced 59% more greenhouse gas emissions than vegetarian diets.

The team concludes that a healthy diet based on unprocessed, largely plant-based foods is also a sustainable one. They point to the 2019 IPCC Climate Change report that suggests a switch to this type of diet could prevent one-fifth of premature adult deaths while reducing diet-related greenhouse gas emissions by 80%1.

Men's eating and drinking habits also play a major role, contributing41% more greenhouse gasses than the food and drink intake of women – largely due to their liking for meat and, to a lesser extent, drinks.

Darren Greenwood of the University's School of Medicine said: "Other studies have suggested that men's higher diet-related emissions reflected their need for more energy. Unfortunately, it appears that they look to get those calories from meat rather than lower impact foods."

The researchers studied the greenhouse gas emissions linked to production and transport of individual foods and brands and used the World Health Organization Recommended Nutrient Intake guidelines to measure the nutrients of those foods.

They then analysed the food and drink consumption of 212 adults recorded online using myfood24 over three 24 hour periods.

The research was funded by a University of Leeds award as part of a programme to encourage interdisciplinary research that addresses the United Nations' Sustainable Development Goals.