Tackling unsustainable food systems can deliver dual health and climate benefits

Tackling unsustainable food systems can deliver dual health and climate benefits

A great review inLimits in sciencehighlights the urgency of tackling unsustainable food systems – reflected in our changing food environment – ​​for both health and the climate.

The paper examines evidence that both obesity and environmental harm result from a for-profit food system that promotes high intake and poor health. The authors say our food environment promotes high-calorie, low-fiber products such as some highly processed foods (UPFs), the highest calorie of which promote weight gain. The same production systems, particularly involving animals, release large amounts of greenhouse gases and pollute land and water.

The comprehensive study, led by Prof. Jeff Holly from the University of Bristol (UK), says that taking the food environment into account can therefore bring double health and climate benefits.

The authors recommend the use of subsidies for healthy foods, taxes and warnings on particularly unhealthy foods, and restrictions on the aggressive marketing of high-calorie, low-fiber products, particularly in low-income communities and to children.

They also challenge the idea that weight loss drugs are a panacea for obesity because they do not address the systemic drivers that also harm the climate.

While obesity is a complex disease caused by many interacting factors, the main reason is the consumption-driven transformation of the food system over the last 40 years. Unlike weight loss drugs or surgery, treating this driver will help people and the planet alike.”

Prof. Jeff Holly, University of Bristol, UK

Diets change land and climate

By 2035, half of the world's population is expected to be overweight or obese - conditions that increase the risk of serious illnesses such as heart disease and cancer. Global warming is now killing one person every minute worldwide, resulting in approximately 546,000 deaths per year during 2012-2021, a 63% increase over the 1990s.

Food production is responsible for a quarter to a third of total greenhouse gas emissions and is the leading cause of land clearing, leading to deforestation and biodiversity loss.

The authors note that even if fossil fuel emissions ended today, current food systems alone could still push global temperatures above the 2°C threshold. Meat production from ruminants is particularly impactful because beef produces far greater emissions than plant-based sources.

“We cannot solve the climate crisis without changing our diet and the way we produce it,” said lead author Prof. Paul Behrens from the University of Oxford (UK) and Leiden University (Netherlands). “To tackle the climate crisis, we must tackle food systems that are driving up emissions and pushing us toward high-energy, highly processed diets full of animal products.”

The review calls for food system reforms to replace energy-dense UPFs with unprocessed foods and reduce the proportion of animal-based foods. They also call for a better classification system for UPFs to increase clarity and emphasize that not all UPFs are the same. For example, processed meat and low-fiber, energy-dense UPFs have worse health and environmental impacts than less energy-dense, high-fiber, plant-rich UPFs.

From willpower myths to systems-level solutions

Obesity increases the risk of premature death and is a leading cause of noncommunicable diseases. For example, a recent study in China found that half of newly diagnosed cancers were linked to obesity, with an alarming increase among younger generations.

The health impacts taken together make obesity one of the biggest causes of global health problems, in addition to its economic burden.

The authors note that while weight loss medications and bariatric surgery are important options for people with obesity, they do not address the larger context that affects entire populations and ecosystems. Concerns also remain about the long-term affordability, safety and sustained global access to these treatments, particularly as obesity increasingly affects younger and lower-income populations.

“The rise in obesity and non-communicable diseases among children and adolescents is alarming,” said co-author Prof Katherine Samaras from St Vincent’s Hospital Sydney, the Garvan Institute of Medical Research and UNSW Sydney, all in Australia. “In adults and children, individual willpower is no match for aggressive marketing campaigns.

“While treatments such as medications and surgery provide important therapeutic options for individuals, they will not replace combating our unhealthy, unsustainable diets and living environments.”

Actions for health and climate

The review brings together current findings from the fields of epidemiology, endocrinology, psychology, public health, nutrition and food systems, economics and environmental sciences. Based on these findings, they recommend:

• Taxes on energy-dense UPFs and sugar-sweetened beverages

• Subsidies to make minimally processed, healthy foods more affordable, funded by taxes on unhealthy foods

• Raise public awareness of the true cost of food by educating the public and health care professionals

• Front-of-pack tobacco labels and restrictions on marketing unhealthy foods to children

• Policies that support healthy school meals and local food sourcing

• Changing your diet to include minimally processed, fiber-rich plant foods and fewer animal products.

Preventing weight gain through healthier food environments would be "far cheaper and less harmful," the authors say, than adapting to the consequences of obesity and climate change or treating individuals rather than changing the system. Obesity-related spending was over 2% of global GDP in 2019. These costs are expected to exceed $4 trillion by 2035 if trends continue.

The authors emphasize that national strategies to combat obesity have so far focused on personal responsibility, based on the perception that it is a lifestyle problem. They note that this has failed to slow the rise in obesity, and they argue that coordinated, science-led reform of the food environment can address both the root cause of obesity and environmental damage.

The authors argue that reframing obesity as a disease should help improve policymaking and shift responsibility from individuals to the systems that influence their decisions.

“Treating individuals – rather than the system that makes them sick – perpetuates the misguided idea that obesity is due to a lack of willpower in individuals,” Prof Holly added. “To reduce the health and climate burden on the food system, governments must first recognize that both climate change and obesity are symptoms of profit-driven, systemic problems – and address the root causes.”

The authors note that although UPFs, obesity and climate impacts are linked by multiple lines of evidence, the underlying mechanisms are complex and several proposed mechanisms remain poorly understood.

They emphasize that further research is needed to clarify causal processes and strengthen the evidence base.

“We risk erasing the gains from health innovation and economic growth if we do not urgently address these twin crises,” Prof Holly added.

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