News release

From: Frontiers

Global food systems driving twin crises of obesity and global heating

A major review in Frontiers in Science highlights how tackling unsustainable food systems—reflected by our changing food environment—is urgent for both health and climate.

The paper reviews evidence that both obesity and environmental harms result from a profit-led food system that encourages high intake and poor health. The authors say that our food environment promotes high-calorie, low-fiber products such as some ultra-processed foods (UPFs)—the most calorific of which encourage weight gain. Those same production systems, especially involving animals, release large amounts of greenhouse gases and put pressure on land and water.

The comprehensive review, led by Prof Jeff Holly at University of Bristol, UK, says that addressing the food environment can therefore deliver double benefits for health and climate.

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

They also counter the perception that weight-loss drugs are a panacea for obesity, as they do not address the systemic drivers which also harm the climate.

“While obesity is a complex disease driven by many interacting factors, the primary driver is the consumption-driven transformation of the food system over the last 40 years,” said Prof Holly. “Unlike weight loss drugs or surgery, addressing this driver will help humans and planet alike.”

Diets reshaping land and climate

By 2035, half the world’s population is projected to be living with overweight or obesity—diseases which increase the risk of serious conditions such as heart disease and cancer. Meanwhile, global heating now kills one person every minute around the world, accounting for around 546,000 deaths per year over the period 2012-2021, up 63% from the 1990s.

Food production is responsible for between a quarter and a third of total greenhouse gas emissions, and is the leading cause of land clearance, which drives deforestation and biodiversity loss.[1-3]

The authors note that even if fossil fuel emissions ended today, current food systems alone could still push global temperatures beyond the 2°C threshold. Ruminant meat production is particularly impactful, with beef generating far greater emissions than plant-based sources.[4]

“We can’t solve the climate crisis without transforming what we eat and how we produce it,” said first author Prof Paul Behrens from University of Oxford, UK and Leiden University, the Netherlands. “To tackle the climate crisis, we must tackle food systems that push up emissions and push us toward energy-dense and highly processed diets full of animal products.”

The review calls for food system reforms to replace energy-dense UPFs with unprocessed foods and reduce animal-sourced foods. They also call for a better classification system for UPFs to enhance clarity—highlighting that not all UPFs are made equal. For example, processed meat, and low-fiber, energy-dense UPFs have poorer health and environmental outcomes than less energy-dense, high-fiber, plant-rich UPFs.

From willpower myths to system-level solutions

Obesity increases the risk of premature death and is a major driver of noncommunicable diseases. For example, a recent study in China found that half of newly diagnosed cancers were obesity-related, with an alarming rise among younger generations.

The health impacts together make obesity one of the largest contributors to global ill-health beyond its economic burden.[5-7]

The authors note that while weight-loss drugs and bariatric surgery provide important options for individuals with obesity, they fail to address the wider environment that affects whole populations and ecosystems. Concerns also remain over long-term affordability, safety, and sustained global access to these treatments, particularly as obesity increasingly affects younger and lower-income populations.

“The rise of obesity and non-communicable diseases in children and youth 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. “For adults and children alike, individual willpower is no match for aggressive marketing campaigns.

“Although treatments such as medicines and surgeries offer important therapeutic options for individuals, they won't substitute for tackling our unhealthy, unsustainable food and living environments.”

Actions for health and climate

The review brings together recent evidence from epidemiology, endocrinology, psychology, public health, nutrition and food systems, economics and environmental science. Based on this evidence, 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 food
• improving public awareness of the true cost of food via educating the public and healthcare professionals
• tobacco-style front-of-pack labelling and restrictions on marketing unhealthy foods to children
• policies that support healthy school meals and local food sourcing
• shifting diets toward 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 note, than adapting to the consequences of both obesity and climate change, or treating individuals instead of changing systems. Obesity-related expenses cost over 2% of global GDP in 2019. These are projected to exceed US$4 trillion by 2035 if trends continue.

The authors stress that national strategies to address obesity have so far focused on personal responsibility, based on the perception of it being a lifestyle issue. This, they note, has failed to slow the rise in obesity, and they argue that coordinated science-led reform of food environments can address both the root cause of obesity and environmental harms.

The authors argue that reframing obesity as a disease should help to improve policymaking, shifting responsibility from individuals to the systems that shape their choices.

“Treating individuals—instead of the system that’s making them sick—perpetuates the misguided idea that obesity stems from a lack of willpower in individuals,” added Prof Holly. “To reduce the food system’s health and climate burden, governments must first recognize that both climate change and obesity are symptoms of profit-driven, systemic problems—and address the root.”

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

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

“We risk undoing the gains from healthcare innovations and economic growth if we don’t urgently tackle these twin crises,” added Prof Holly.

ENDS

Notes to editors:

More on food system links with climate:

1. UPF manufacturing relies heavily on ingredients derived from large crops such as sugar, maize, and wheat along with animal products such as powdered milk, eggs, and processed meats. The additional food intake needed to maintain obesity increases emissions by 20%.
2. Food production is the biggest single cause of land clearance, losing natural habitats and biodiversity. Deforestation worsens the risk of climate change, destroying an important mechanism of removing carbon dioxide removal from the air. Transforming areas like wetlands can even release carbon dioxide that was previously locked away.
3. Producing 100 g of protein from beef generates around 50 kg of carbon dioxide equivalent, compared to 0.84 kg from beans.

More on food system links with obesity:

4. About three-quarters of agricultural land use, and the associated emissions, is due to the demand for animal products, such as meat and dairy.
5. Unhealthy foods, including energy-dense, low-fiber UPFs, have been shown in randomized controlled trials to be associated with increased energy intake and weight gain, particularly in lower-income populations. They are also associated with higher risks of obesity and non-communicable diseases across multiple cohort studies. Early evidence shows that these risks disappear for plant-rich, high-fiber, less energy dense UPFs.
6. Obesity, alongside many of these diseases, is now rising in children.
7. Obesity also drives diseases such as type 2 diabetes, fatty liver disease, osteoarthritis, sleep apnea, and impaired immune function, many of which are now appearing at younger ages.