This article will explain why sustainable diets are essential for human and environmental wellbeing, and our survival on this planet. We’ll also take a look at some of the harms, benefits and health implications of our current food systems, as well as steps we can take towards positive change.

 A failing food system

The UN Food and Agriculture Organisation defines sustainable diets and sustainable agriculture as having low environmental impacts, while promoting the health and food security of present and future generations. They must preserve biodiversity and ecosystems, be culturally acceptable, affordable, and nutritionally safe, while optimising natural and human resources ¹.

Unfortunately, what has evolved instead is a network of extractive systems, covering 40% of Earth’s land surface and most of the oceans, aimed at maximising profits and yields, while promoting eating patterns which are far from sustainable. It is heavily dependent on fossil fuels, synthetic chemicals and fertilisers, while rapidly depleting our soil and water.

Agriculture generates at least 30% of human greenhouse gas (GHG) emissions, half of which are due to the grazing of over two billion ruminant livestock. It is also the biggest cause of habitat destruction, species decline and extinction, including fish and pollinators². Vast crop monocultures, giant concentrated animal feed lots, and long supply chains make this system productive in the short term, but extremely vulnerable to diseases, extreme weather, rising oil prices, armed conflicts, and other long-term challenges.

At present, we’re producing enough to feed the worlds’ 8 billion people, an impressive achievement. However, a full third of all this food is wasted, and distribution is strongly skewed towards wealthier nations. As a result, two billion people are malnourished or even starving, while 2.5 billion are overweight or obese². Even in Australia, a net food exporter, around 3.7 million households are food insecure³. These systemic failures have serious environmental and social consequences.

The global spread of the Western diet

Australia, like other wealthier nations, has seen a slow shift away from kitchen gardens and home cooking, towards excess meat and ultra-processed foods (UPFs), high in fat, salt, and sugar. The global spread of this Western diet since the 1960s correlates with new food technologies, and business decisions taken within the food industry, to promote products with cheaper ingredients, longer shelf lives, and higher profit margins. Their advertising budget of around $550 million annually in Australia is poorly regulated and often targets children⁴.

The NOVA food classification system

Large food corporates promoting UPFs also generate most of the world’s plastic waste. Coca-Cola alone makes over 100 billion single-use plastic bottles every year, which usually end up in landfill or waterways⁶.

A meaty issue

Meat is a good source of nutrients including protein, haem iron, zinc, and B12, particularly for younger age groups, women, and during pregnancy. However, there are strong health and environmental reasons to reduce our meat intake. A main drawback, especially of beef, is a heavy environmental footprint, and relatively low protein yield.
Per 100-gram of dietary protein, beef produces 50kg of GHG equivalents (a quantity of GHG can be expressed as CO2e by multiplying the amount of the GHG by its GWP), compared to pig at 7.6kg/100gm, poultry 5.7kg/100gm, and tofu 2kg/100 gm protein.

Despite this, around 80% of the worlds’ farmland is devoted to either livestock grazing, or growing livestock food crops like soya and corn. Consumption is wealth and culture related, with Australians among the world’s biggest meat eaters at over 100kg per person per year, half of which is poultry. Bangladesh averages 4kg per person per year². Australian Dietary Guidelines recommend eating no more than 20kg of red meat per year. Processed meats such as bacon and salami, are Class 1 carcinogens, increasing the risk of breast and bowel cancer⁷.

How Western diets are impacting our health

Western diets, and the systems that underpin them, are also a major factor in the global rise of overweight and obesity, which has tripled in the past 50 years to around 2.5 billion adults worldwide. Australia ranks in the top ten, with one third of adults overweight, another third obese, with higher rates in Indigenous populations¹¹. It has given rise to thousands of weight-loss products, diets, and treatments, including almost 40,000 bariatric surgical procedures annually⁸. Obesity costs our health system around $11.8 billion each year, a figure that is expected to rise to $88 billion by 2032 if current trends continue⁴.

UPFs displace healthy foods, and the higher the intake, the higher the risk of weight gain and obesity. Each 10% increase in dietary UPFs may be associated with a more than 10% risk of heart attack and stroke⁹. One recent survey of household food budgets showed that 60% was spent on UPFs¹⁰.

Non-communicable diseases (NCDs) account for around 90% of all deaths in Australia, with being overweight second only to smoking as the greatest risk for prolonged disability and early death¹¹. Obesity is also linked to a range of conditions including hypertension, stroke, ischaemic heart disease, diabetes, fatty liver, sleep apnoea, arthritis, and ten common cancers. Treating these conditions consumes a considerable amount of Australia’s health budget.

Women are more likely to develop polycystic ovary syndrome and experience reduced fertility if they are overweight. This is linked to chronic raised insulin, and decreased levels of sex-hormone binding globulin. These conditions are likely to improve with dietary changes, including a modest 5% weight loss¹². Pre-pregnancy obesity increases the risk of gestational diabetes and of maternal preeclampsia, while healthy plant-rich diets seem to have a protective effect¹³.

Calling for a better future for all

Improving the nutrition and eating habits of Australians must become a priority for all levels of government (which) need to consider the full complement of measures open to them…ranging from increased nutrition education and food literacy programs, through to mandatory food fortification, price signals to influence consumption and restrictions on food and beverage advertising to children.

– AMA. Nutrition-2018

So how do we move towards having a healthier and more sustainable diet? Prevention is key. Virtually all our major health and medical associations are calling for action and have strong public support. A “National Obesity Strategy 2022-2032” exists, but we still lack basic measures such as a sugary drinks tax, mandatory food health labelling, and a ban on the predatory advertising of UPFs to children. At least 50 other nations have successfully enacted such measures, but in Australia, industry interference, fragmented advocacy and conflicting political agendas have delayed effective action. Backing healthy lifestyle messaging with effective legislation would return around $6 per public health dollar invested, with triple bottom-line benefits to health, the environment, and budgets. Updated NHMRC and Australian Dietary Guidelines must underpin a national approach to healthy sustainable diets, with provision of a free national online counselling service, like Quitline for smokers¹⁷. The education and involvement of health professionals has been, and remains, absolutely critical. Role models include Dr James Muecke AM, Dr Gary Fettke, and Dr Sophie Scamps MP, who recently proposed a national bill to protect children from unhealthy food advertising⁴.

Sustainable diets are the single best way to optimise human and environmental health. To reflect environmental as well as health impacts, Western dietary patterns must transform to plant-rich or planetary¹⁴ diets, with at least twice the proportion of minimally processed plant-based foods, including fruits, greens, legumes, nuts, and grains, and less than half the meat. This simple switch creates significant gains in health and life expectancy¹⁵, while helping alter priorities in the farming and retail sector, away from centralised industrial towards more localised low-impact networks of agroecological production¹⁶, potentially halving GHGs from the food sector⁴. We face many challenges, including climate change, food insecurity, increasing NCDs and stretched budgets, but one thing is certain — shifting to sustainable diets and food systems is an essential step towards economic security, environmental repair, and flourishing good health for all.

Dr Michael Schien, MBBS Dip Anaes. (UK). DipRACOG, FRACGP. GP & Chair of Doctors for the Environment’s Diet Planet Working Group.