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Built to Bite:

RUMS Review

RUMS Review

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Built to Bite:

The Impact of built environments on obesity and accessibility to food 

Written By Charlotte Muller

Have you ever wondered why the first thing you see in a Lidl is the bakery? 

Obesity has become one of the most pressing global public health challenges of the 21st century. As of 2022, 1 in 8 people worldwide are now living with obesity, more than double the rate since 19901. While this rise is often attributed to individual lifestyle choices, such as diet and physical activity, an increasing amount of research suggests that these behaviours are not as independent as one might think. Rather, they are shaped by our surroundings, otherwise known as our built environment. 

Urbanisation has transformed not only our cities, but also our food systems. In many urban areas, energy-dense, highly processed foods are cheaper, more visible and more aggressively marketed than healthier alternatives.

At the same time, aspects of the built environment, such as neighbourhood design and transport infrastructure, can either encourage or restrict active lifestyles. 

But this issue extends beyond simple convenience. Urban environments influence dietary behaviours in multiple ways: the increasing availability of ultra-processed foods, the emergence of food deserts and food swamps, and the subtle influence of choice architecture. These effects often interact with socioeconomic factors to specifically affect vulnerable populations. Understanding these drivers is essential for developing effective and equitable strategies that consider the wider context of obesity to address this global epidemic.

Ultraprocessed food and what are food environments

A food environment consists of the physical, political, economic and socio-cultural contexts that influence what people buy, prepare and consume. It shapes dietary choices through food accessibility, affordability and advertising. The food environment is recognised as a key determinant for the prevention of obesity and other diet-related non-communicable diseases2. Regions characterised by abundant fast-food outlets, limited supermarket access and scarce fresh produce stores tend to have higher obesity rates. 

Ultraprocessed foods are so energy-dense because of how they’re engineered on a chemical level. They often combine refined sugars and added fats, which have ~9kcal per gram. By combining both in large amounts, manufacturers create foods with extremely high caloric density. What’s more, this process strips away water and fibre, which normally reduces energy density since water adds weight and fiber slows digestion which increases satiety.

Ultraprocessing also structurally changes food by breaking down cell structures, making nutrients more bioavailable and absorbable3. This results in faster digestion (so less energy is spent on digestion) and, therefore, quicker glucose spikes and weaker satiety signals. 

Finally, ultraprocessed foods are engineered to encourage overconsumption, as they’re often soft and easy to chew, and therefore easily digested. This reduces the release of the satiety hormones GLP-1 and PYY, and reduces gastric stretching, which means an individual can consume more calories before feeling full. All these factors result in ultraprocessed foods, which are already extremely calorie dense, being consumed in high volumes, making for an extremely high-calorie meal. 

Navigating food swamps and deserts 

Food swamps are defined as residential areas with an abundance of non-nutritious food options such as corner shops or fast-food restaurants. They’re characterised by an overwhelming abundance of high-calorie, low-nutrient processed foods4. Given their high concentration of calorie-dense foods, food swamps are directly linked to obesity. 

Food deserts, on the other hand, are areas that have limited access to fresh food. Food deserts mean that an area is deprived of fresh produce and healthy options, increasing the risk that the population will have a less healthy diet with a higher concentration of ultraprocessed foods5. 

Food swamps and food deserts are different sides of the same coin. The key difference between food swamps and deserts is that a food swamp specifically focuses on an over-allocation of unhealthy food, whereas a food desert highlights the noticeable absence of nutritious options. For example, someone might live in an area with 10 fast-food restaurants in a mile radius, yet still have access to supermarkets with fresh produce and nutritious options. That would be considered a food swamp. In another case, someone might be living far from a supermarket so cannot conveniently buy fresh produce or healthy items, and would therefore be living in a food desert.

Beyond availability, choice architecture actively steers consumers towards high-calorie food choices. Choice architecture is structuring environments to influence decisions, often used in advertising to influence a consumer. This can include the accessibility, salience, colours, information and ordering of items. Subtle aspects of choice architecture can have significant effects on public health24. For example, if chocolate bars are easily accessible and highly salient (e.g. located at the checkout rather than the middle of a supermarket aisle), people are more likely to choose them.

Appealing packaging, sometimes even perverted with targeted health-related claims and cunningly placed around the store, all work to increase purchasing and consumption6. Multiple examples have been identified in which false health connotations, or ‘health-halos’7, serve to increase purchasing. By using false advertising to get ahead in sales, food companies can blind consumers to what they’re actually eating and disillusion them. 

Impact on vulnerable populations

Food deserts are often used as an indicator of the vulnerability of an area to obesity. They are often assessed by measuring the distance between people’s homes and supermarkets, which has been found to vary significantly with a neighbourhood’s ethnic and socioeconomic composition. 

When considering an individual’s socioeconomic position and how it relates to their accessibility to food, low-income families appear to place a premium on time and convenience when it comes to food purchasing decisions20 due to factors like unpredictable work schedules or increased burdens due to poverty. Time scarcity for cooking and shopping is a significant barrier to the uptake of a health-promoting diet. Increased time spent on food preparation and cooking has been linked to higher quality diets and health status21.Furthermore, an increase in time spent preparing, cooking and cleaning up from meals at home is associated with healthier patterns of food consumption measured by an increase in fruit and vegetable consumption, decreased spending on food consumed outside the home, and fewer visits to fast-food restaurants. 

An underlying tenet of the Healthy Food Financing Initiative, a $400 million investment in the US intended to bring affordable healthy foods to food deserts22, is that the lack of access to healthy foods is an important cause of obesity and chronic disease in minority populations.

However, another variable must be considered - cost. When store prices were lower, the obesity rates of the shoppers were higher. The inverse association between store prices and obesity suggests that those who did their major food shop at a low-price shop have a higher chance of being obese. 

An explanation for this association is that residents with low socioeconomic status, and consequently higher rates of obesity, shop at low-price shops23. Another explanation for this association is that price level captures underlying differences in store environments, such as differences in marketing of healthy versus junk foods. This links to the earlier idea of choice architecture. Compared to expensive stores, low-price stores had fewer displays to promote healthy foods and junk foods were more visible from the entrance, in opposition to the prominent display of fruits and vegetables in high-price stores. 

Altogether, it’s clear that high-price supermarkets actively market healthy foods, while low-price shops actively market unhealthy food. This might be because high-price shops know that their customer base is comprised of those in higher socio-economic brackets, and are therefore more able to seek out more expensive items such as produce or high-quality nutritious items. Low-price shops are not able to stock produce or healthier items in the first place because they cost more to sell. This creates a massive barrier for those seeking cheaper options while still trying to be health conscious. Over time, this narrowing of choices for those shopping in low-price shops means their diet will consist of higher-calorie items, eventually contributing to weight gain and potentially obesity.

Built environments

As the number of obesity cases rises, research into the causes of obesity has diversified, including the drivers of ‘obesogenic’ behaviours that lead to a chronic surplus in energy intake compared to expenditure9. While earlier research has generally focused on individual-level factors such as motivation or genetics, more recent epidemiological research places obesity into the larger socio-ecological context where the environment plays a major role in shaping individual behaviours10. 

In the past two decades, the built environment has emerged as a conceptually important determinant of obesity8, by driving obesogenic behaviours11. It encompasses all aspects of an individual’s surroundings which are man-made or modified such as buildings, parks and infrastructure. It’s also a subset of the ‘exposome’ - all exposures and lifestyle behaviours of an individual over a lifetime12. 

In one study, two main pathways are imagined where the built environment can contribute to health outcomes: behavioural and direct exposure13. While behaviour refers to obesogenic behaviours, such as physical activity and diet, direct exposure includes biological responses to environmental exposures (like how air pollution in a busy city might affect weight through inflammation). These two pathways are not mutually exclusive, increasing the complexity of built environmental studies. 

An example of where these two pathways can intersect is the ‘walkability’ of an area. Of course, while the choice to walk is behavioural, it is heavily shaped by environmental characteristics known as the ‘D variables’14, including density, diversity (of land uses), design, destination accessibility and distance to transit. Environments with a low population density, poorly connected streets and limited destination access can reduce opportunities for incidental physical activity, making it much less walkable than another built environment15. This essentially takes away the choice to walk from a person, eliminating easily accessible physical exercise from their routine. In this case, a more conscious choice to exercise is necessary, which many people don’t have the time to consider, nor the money to attend expensive exercise classes or gyms.

Neighbourhood designs that make it easier to engage in active forms of transportation, including walking and cycling, are hypothesised to increase physical activity as it is far more convenient and easier to incorporate into everyday life. Studying 14 cities across 10 countries, the International Physical Activity and Environment Network study found that residents living in the most activity-friendly neighbourhoods had up to 89 additional minutes per week of moderate to vigorous physical activity compared to the least activity-friendly neighbourhoods studies25. Similarly, another study found that those living in the most versus least walkable neighbourhoods performed an average of 82.6 minutes more per week of moderate to vigorous physical activity16. Based on these studies, residents that live in areas more conducive to walking appear to be more likely to achieve physical activity targets (150 minutes of moderate intensity activity per week) according to NHS guidelines17. 

Another study showed substantially lower rates of obesity in adults living in high walkability areas18.The adjusted rates of obesity in a sample of the population remained stable in highly walkable areas over a 12 year period between 2001 and 2012, while rates significantly increased over time in less walkable areas19. It is vital to consider built environments as major risk factors for being overweight and obese, as small everyday factors build up over time and can lead to massive health complications. 

Conclusion

Obesity cannot be reduced to a matter of personal responsibility alone. The environments in which people live fundamentally shape their dietary behaviors and physical activity. From the engineered appeal of ultra-processed foods to the presence of food deserts and swamps and the design of neighbourhoods that limit or enable physical activity, the built environment consistently nudges people towards certain choices over others. 

It’s important to consider that these influences are not experienced equally. Socioeconomic constraints amplify the impact of obesogenic environments, narrowing the range of realistic choices available to more vulnerable populations. Addressing the obesity epidemic therefore requires a shift in perspective. Policies that improve access to affordable, nutritious food, regulate food marketing and prioritise walkable, activity-friendly urban design are essential.Obesogenic lifestyles are not as simple as an individual’s personal choice. People are a product of their environment, therefore it’s vital to consider how structural factors ultimately influence health.

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References

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