(1). Excess weight is a risk factor for the development of many non-communicable diseases such as cardiovascular disease, stroke, type 2 diabetes and certain types of cancer. Diet-related chronic diseases are the leading causes of preventable death in Australia and 5.5% of Australia's burden of disease is attributable to obesity (1)(2). Despite the significant impact obesity has on population health, policies and programs struggle to create long lasting behaviour change in individuals, and the prevalence of obesity is predicted to continue increasing (3). There has been action at all levels of government about the issue. The federal government established the National Preventative Health Taskforce to develop strategies to tackle obesity, with states, territories and local governments also developing initiatives for obesity prevention (4).
Another major public health challenge that is expected to become increasingly problematic is anthropogenic climate change due to greenhouse gas emissions (5). As the climate becomes more unpredictable with more frequent extreme weather events, water security is anticipated to become a major source of international conflict. Changing temperatures will impact where and when food is able to be grown, and less water will be available to grow it. Together these things have the potential to lead to widespread fresh food shortages (3). Despite overwhelming scientific consensus, anthropogenic climate change remains a politically partisan issue in Australia. This causes significant challenges making it a priority on the political agenda, with policies generally met with criticism (6). However, there is potential to mitigate climate change through policies and programs targeting other, more politically aggregable areas of public health.
There is a growing body of evidence suggesting that climate change be partly mitigated with programs and policies aimed at reducing obesity rates (3). A population where 40% of people are obese requires 19% more food than a population free of obesity, placing an enormous burden on both the health and environment of Australia and the world. (7). According to Van Loo, Hoefkens and Verbeke, people tend to be of the belief that food packaging has the greatest environmental impact. Surprising, consumption of meat places more pressure on the environment than the production and disposal of food packaging (2). Livestock accounts for 13% of Australia's anthropogenic greenhouse gas emissions. The majority of this is from sheep, beef cattle and dairy cattle (8). These emissions occur due to a combination of deforestation to make land for grazing and growing feed, fermentation of waste, and fossil fuel consumption for the transport and processing of the livestock (9). Besides meat, almost a third of Australia's food related greenhouse gas emissions are due to energy dense, nutritionally poor processed food (10). Consumption of excess kilojoules not only contributes to the development of obesity but results in further environmental demand to produce unnecessary food (2). However it is only recently that the environmental impacts of this shift in diet have been considered (10).
The Food and Agriculture Organization of the United Nations defines a sustainable diet as a diet “with low environmental impacts which contribute to food a¬¬nd nutrition security and to healthy life for present and future generations (11)(p83)”. They suggest that an ideal diet should be environmentally protective, nutritionally adequate, safe, accessible and culturally acceptable, promoting both individual and environmental health (12). Springmann, Godfrey, Rayner and Scarborough (5) developed found what they term a ‘healthy global diet' made up of 5 portions fruit and veg, less than 50g sugar, a maximum of 43g red meat, and 2200-2300 kcal. World-wide adoption of these guidelines would result in 5.1million deaths avoided per year and 79 million years of life saved, reducing deaths due to cardiovascular disease, stroke, cancer and type 2 diabetes in 2050 by 12%. Springmann et al also predicted that food related greenhouse gas emissions would only rise by 7% by 2050 if these guidelines were followed globally, a huge difference to the 51% increase predicted following current dietary practices (5). The current Australian dietary guidelines recommend 5 portions of vegetables, 2 portions of fruit and 3 serves of protein (including up to 195 grams red meat) They also recommend limiting added sugars and excess kilojoules, but do not specify an amount (13). The Australian dietary guidelines are similar to the healthy global diet although they do not recommend limiting intake of red meat. It was proposed that a specific guideline be included about eating an environmentally protective diet however this was highly contested by industry so the information was relegated to a one page appendix (2). The appendix briefly discusses the environmental benefits of eating seasonally and limiting processed foods (13).
Some of the barriers the National Health and Medical Research Council identified as impeding people adopting the Australian dietary guidelines are the affordability and availability of food, poor communication of the guidelines, low level of food literacy, dietary preferences, and conflicting messages. They specifically identified the advertising of processed foods as one such barrier (13). Over the last few decades the diets of Australians have been changing to be higher in fat, sugar, energy intake and animal product, and lower in fresh produce (3). Highly processed foods and beverages that have minimal nutritional value and high amounts of salt, sugar and fat are more durable, convenient for the consumer and are often more appetising than fresh produce. They are heavily marketed by supranational corporations, further increasing their appeal. These factors have led to the shift in dietary patterns seen in Australia and across much of the world (14). In 2014-15, 93% of Australian adults ate less than the recommended 5 daily serves of vegetables, and 50% ate less than two serves of fruit. As much as 35% of Australian adults' daily energy intake came from foods high in saturated fats, sugar or salt (1). There is a plethora of evidence showing that higher consumption of these types of food is linked to increased incidence of obesity and related non-communicable diseases (3).
Individual attitudes and beliefs that lead to poor dietary choices and higher greenhouse gas emissions are formed through a combination of the social, cultural, political and economic environment that individuals belong to. It is difficult for an individual to overcome multiple barriers in their environment to make long lasting changes to their diet. Therefore, policies that shape these environments to encourage healthier, more sustainable choices generally have the greatest impact (3). There are many different strategies a government can use to help facilitate healthier, more sustainable food choices across the population: policy measures, taxes or subsidies, regulations on food supply and purchase, supporting the development of alternative products, monitoring and program evaluation, education and communication (7).
People are more likely to successfully change to a diet that is similar to their own, therefore encouraging slow change, swaps and ensuring that health promotion messaging is culturally appropriate are vital (15). Although many campaigns have been run promoting a specific amount of servings of fruit and vegetables each day, the most successful have focusing on simply increasing frequency of consumption rather than aiming for a set target (16). A program that has been highly successful at increasing fruit and vegetable consumption in children is the Stephanie Alexander Kitchen Garden program. The program began in Melbourne in 2001 and has expanded across the country, currently running in over 1000 primary schools nationwide. Children spend time each week gardening and cooking, learning how to grow, harvest and prepare seasonal food (17). An evaluation of the program conducted in 2013 found that it has led to a measurable improvement in the children's food choices, nutritional knowledge, and willingness to try new foods. Parents surveyed also reported their children showed greater interest in cooking at home (18). Developing familiarity with fresh produce early in life is vital, as familiarity plays a large role in food choices across all stages of life (12). Despite being such a successful program, it does face ongoing challenges securing funding and remaining a priority with teachers integrating the program into an already packed national curriculum with a focus on testing scores (18).
It is important to facilitate people's ability to make healthy and sustainable dietary choices not only as children, but throughout their lives. Self-regulation refers to a person's motivation and control over their choices. It has been shown that choices that require a person to self-regulate such for opting for water over their favourite sugary beverage reduces their ability to self-regulate subsequent choices (19). This is why it is so important to change to environment to make healthy choices easier and more convenient(15). Current Australian guidelines mandate that all packaged foods display nutrition information on the front of the packaging to assist with quickly identifying healthy food choices. Presently this information is required to be displayed as a percentage of daily intake, however studies have shown that the use of a ‘traffic light' system is more readily understood (20). The traffic light system involves classifying food and beverages as green (best choice), amber (choose carefully and in smaller portions) and red (limit intake). This system is used as part of the City of Melbourne's “Green Light, Eat Right” program and the Victorian Government's Healthy Choices guidelines. As part of these programs the traffic light system has been implemented across multiple recreation centres, health services, schools and universities. This system has led to a sharp reduction in the amount of ‘red' products being purchased and increased sales of ‘green' and ‘amber' products, showing that making choices simple does lead to an increase in positive health choices (21). The introduction of carbon footprint labelling alongside nutrition labelling could also be considered to increase consumer awareness of the environmental impact of their food choices (2). Despite (or perhaps because of) the success of the traffic light labelling system, the food and beverage industry has been lobbying to try and prevent widespread adoption. The system empower consumers by providing straightforward information about the nutrition content of different foods rather than requiring them to compare confusing labels and serving sizes (22).
Another measure that is the source of much debate and industry lobbying around the world is a tax on sugar sweetened beverages. Sugar sweetened beverages cause weight gain due to their poor ability to satiate compared to their energy content and are often consumed to satisfy thirst rather than hunger, leading to overall excess energy intake (23). There are many studies showing that increasing the price of sugary beverages reduces consumption, and while there are limited studies currently available on the impact of such a tax on population weight, those that have been conducted report some reduction in weight (24).
The food and beverage industries include multiple supranational corporations with substantial economic power and political influence. As the industry is comprised of such powerful corporations there are significant legal and political challenges involved in tightening the regulations on the marketing of unhealthy food (19). These corporations lobby politicians for policies that are good for them and maintain a positive public opinion of the industry, for example framing the debate around obesity in a way that presents these companies as part of the solution. Unfortunately, this can lead to policies that favour business over health, undermining public health efforts (25). The food and beverage industry tend to use strategies similar to those used by the tobacco industry, aiming to increase their profits and promote deregulation of the industry. It is vital that governments and public health organisations pay attention to the lessons they learnt from tobacco control efforts to combat industry opposition to efforts aiming at reducing the prevalence of obesity (26).
Given that obesity is such a complex issue, there are many different experts, advocates and groups seeking to address the problem. Unfortunately, without a principal organisation to develop a response to the issue it has proved challenging for these groups to develop a cohesive agenda. This has led to a lack of consistency in messaging and proposed action (26). The fresh produce industry faces similar challenges. Fruit and vegetable producers generally operate separately, making generic promotional campaigns about fruit and vegetables unlikely to occur on a scale required to have significant reach and impact (16). In comparison, corporations producing highly processed foods generally have substantial advertising budgets (25). Use of mass media can lead to positive changes to health behaviours across the population, particularly when used in combination with other health promotion measures. Another way the media can be used to encourage positive health behaviours is a media advocacy campaign. This involves working with the media to shape the presentation of public health issues in an informative way that is in line with current public health knowledge and campaigns (27).
Obesity and climate change are major health issues which require multiple approaches in order to solve. Public health measure promoting healthier dietary choices including limiting consumption of red meat, processed food and excess calories are one such approach. In doing this, health promotion strategies aimed at reducing the prevalence of obesity can play a role in mitigating climate change. Through a combination of policy, regulation and education we can work towards decreasing obesity in the population. Successful programs such as Stephanie Alexander's kitchen garden program and the traffic light packaging labelling system need to be supported by the government and the community in spite of industry opposition.
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