Why Diet-Related Disease Isn’t as Simple as “Unhealthy Choices”

Most of the world’s population now live in countries where overweight and obesity kills more people than lack of food. Discover the many drivers behind diet-related diseases in the UK.

The saying ‘you are what you eat’ may be an old one, but modern science provides overwhelming evidence for it. Countless research studies have concluded that diets rich in vegetables, fruits, pulses, nuts, seeds, and olive oil, with moderate amounts of fish, meat, and dairy, promote long life and good health.¹ Conversely, diets heavily based on energy-dense foods high in fat, sugar and salt have been strongly linked to obesity, type 2 diabetes, high blood pressure, heart disease, arthritis, and various cancers. But despite this knowledge becoming more commonplace, rates of diet-related diseases are soaring around the world.

For instance, obesity rates have nearly tripled since 1975, and most of the world’s population now live in countries where overweight and obesity kills more people than lack of food.² In the average European country, the proportion of people living with overweight or obesity has risen to 53%, but in the UK - the focus of our case study here - the numbers are particularly high, at almost 64%.^3,4 The combined costs of this – including reduced productivity, lower life expectancies, and the National Health Service funds – are thought to reduce UK GDP by around 3.4%, equivalent to every UK person paying an additional £409 in taxes each year.⁵

Aside from health and economic implications, people experiencing overweight and obesity are slo often met with judgement and social stigma. There is a widely held idea that their situation results from laziness, a love of junk food, and a lack of willpower. But this simplistic - and judgemental - explanation fails to consider how extraordinarily complicated obesity is: a truly ‘wicked problem’ that is tangled up in many different physiological, environmental, and social issues. From unequal access to fresh food to enormous corporate marketing budgets, and even biological differences in our microbiomes, our health is the result of far more than individual willpower and dietary choices.

Read more about how diet affects longevity
 

Good food costs money (and time)

Healthy food is expensive. Fruits and vegetables, for example, cost more than twice the price per calorie than food high in fat and/or sugar.⁶ Ana Maria Narvaez-Olaya, Senior Policy and Advocacy Officer at The Food Foundation, told FoodUnfolded, “The harsh reality is that purchasing healthy, sustainable food is financially out of reach for many households. Meeting the UK government's recommended healthy diet would cost the poorest fifth of the population 50% of their disposable income, compared with just 11% for the least deprived fifth.⁶ This economic tension forces individuals to compromise on nutrition and opt for cheaper, less nutritious alternatives. There is an urgent need to reorientate the food system and make nutritious choices affordable to all.”

But it’s not just the ingredients that are out of reach. Preparing meals from scratch using fresh ingredients requires energy and cooking appliances, and not everyone has access to these. In the UK, spiralling energy costs are forcing more people to choose between ‘heating or eating’, and around 4.8 million people lack at least one essential household appliance, such as a cooker, freezer, fridge or washing machine.^7,8

Not surprisingly, diet-related disease is disproportionately higher in low-income groups than the more comfortably off. Compared with the most affluent 10%, those belonging to the most deprived 10% in the UK are 2.1 times more likely to die from preventable heart disease; 1.7 times more likely to die from preventable cancer; 3 times more likely to have tooth decay at five years of age; and nearly twice as likely to be overweight or obese by age 11.⁹

Shopping around for affordable, healthy ingredients and preparing fresh meals from scratch can also take a lot of time. For those with multiple jobs, shift work, caring responsibilities or long commutes, speed and convenience often have to be prioritised over nutrition. This can lead to a reliance on ready-prepared, ultra-processed foods, which growing evidence is associating with particularly harmful health effects.¹⁰

You can’t eat what you can’t access

Food landscapes vary enormously, so even when money isn’t a problem, some people have more difficulty accessing healthy foods. Across the UK, millions of people are trapped in ‘food deserts’: places where poor public transport links, lack of large supermarkets and unavailable online deliveries can make it almost impossible to physically access good food.¹¹ In the North East of England, almost half (45%) of local neighbourhoods fall into this category.¹²

On the flip side, junk food can be all too easy to come by: an average of 1 in 4 (25.6%) places to buy food in England are fast-food outlets. But this distribution isn’t equal: there is a clear link between poverty and the density of fast-food businesses, which make up 21% of food outlets in the least deprived local authorities compared with 31% in the most deprived.⁶
 

Meanwhile, in schools, the rising costs of ingredients, labour and energy are making it increasingly challenging for caterers to provide recommended nutrient-dense foods (such as fresh fruit and salmon); in 2018, the Soil Association estimated that up to 60% of secondary schools are non-compliant with the School Food Standards, largely due to a lack of government monitoring.¹⁴

Knowledge is power

Even when access is not an issue, it requires knowledge to understand which foods are healthy (which can require deciphering misleading on-pack claims) and how to prepare them into balanced meals.¹⁵ Across the UK, food education has declined thanks to squeezed budgets, limited numbers of food educators, and the removal of the ‘food’ A level in 2016.^16,17,18 In 2018, the school inspection body Ofsted found that only 26% of schools are implementing the practical cookery requirements of the National Curriculum.¹⁴ Coupled with the decline in home cooking, this is causing more children and young people to grow up without kitchen confidence, setting a trend for an adulthood relying on convenience foods.¹⁹ In Britain, one survey found that the average number of meals people can cook from scratch without a recipe was seven, and more than a third of people (38%) say they wouldn't be confident cooking fresh ingredients without a recipe.²⁰

Louise Davies, Founder of the Food Teachers Centre, told Food Unfolded, “The huge variation in the provision of food education across the UK means that many children are not receiving the opportunity to learn about what constitutes a healthy, varied diet, as well as develop their food skill repertoire. This could greatly hinder their ability to adopt healthy lifelong dietary habits, and widen health inequalities.”

Our intrinsic differences

Even if two people eat identical meals, the unique differences in their gut microbiome (the trillions/billions of bacteria that live in our intestines) may cause them to process it very differently. Increasingly, scientific studies link these bacterial differences with our likelihood of developing diet-related diseases. People living with obesity, for instance, have been found to have higher proportions of species, such as Lactobacillus reuteri, that have been associated with weight gain in animal studies.²¹ Reasons for this are thought to include certain microbial species being more efficient at harvesting energy from foods, impacts on the production of appetite-regulating compounds, and influences on the rate of energy expenditure.²²

Obesity also has a strong genetic component. For common obesity (not caused by a single genetic mutation or a disorder), hundreds of variations affecting many different genes have a small but cumulative effect in determining an individual’s genetic risk for obesity.²³ These genes are associated with factors that include energy balance and heat production, the development of fat cells, and appetite-regulating hormones.²⁴ Although having a high genetic risk score for obesity doesn’t necessarily mean an individual will develop obesity, it makes a person considerably more vulnerable to a ‘junk food’ environment.

We eat with our eyes

From every direction, we are bombarded by advertisements for junk foods, whilst promotions of fruit and vegetables are barely noticeable. In the UK, for instance, 1.2% of food and drink advertising (minus alcohol) in 2015 was spent on vegetables, compared with 22.2% for cakes, biscuits, confectionery and ice creams.²⁶ And around one-third of ‘buy one get one free’ and multi-buy deals are on unhealthy food, with just 3.8% on fruit and veg.²⁷ Food companies invest heavily in enticing marketing campaigns, with children’s products often featuring popular cartoon characters or ‘free’ gifts. And it works: studies have found that exposure to junk food advertising increases both short-term calorie intake in children and purchasing of high-fat, salt or sugar foods.^28,29
 

Read more in 'When Does Food Processing Go Too Far?'

Yet, despite strong public support for greater restrictions on junk food advertising, the UK Government announced that it would delay plans to ban multi-buy deals and a ban on TV advertising for foods high in fat, salt or sugar before 9pm (when children are more likely to see them).³⁰ The proposals, originally due to become law in January 2023, have been put back until 2025 at the earliest.³¹

Hard-wired for calories

Biologically speaking, our bodies are adapted to an environment of food scarcity, hard-wiring us to seek out and get pleasure from energy-dense foods.³² Storing excess calories as body fat was an evolutionary strategy to survive lean times. But now that we are surrounded by cheap calories, this has backfired. Eating junk foods such as industrially-produced chocolate cake causes our brains to release the chemical dopamine, giving us the sensation of reward. Over time, the brain can become desensitised to this response, meaning that more junk food is needed to produce the same effect, causing us to eat more.³³ On top of this, processed and ultra-processed foods have been shown to be less satiating (so we feel less full), to have a greater impact on blood glucose levels, and to cause people to eat more compared to home-cooked meals.^34,35

When our biological drive to seek out calories is combined with the relentless marketing of unhealthy foods, this has created what has become known as a ‘Junk Food Cycle.’ As Henry Dimbleby, co-founder of the Leon restaurant chain explains in the UK’s 2020-2021 National Food Strategy report, “We have an in-built preference for foods that are high in calories – in sugar and fat. They not only reward us with disproportionate pleasure, but when they are soft, energy-dense (low in water content) and low in insoluble fibre, they also fill us up less quickly than other foods. Food companies have spotted this. They have increasingly focussed their Research and Development and marketing on these foods. We eat more, they spend more, we eat more, they spend more, and we get sick. It is what is known as a reinforcing or escalating feedback loop. A vicious cycle. Only by breaking this ‘Junk Food Cycle’ can we begin to make progress on tackling diet-related diseases.”

Food companies shouldn’t be given all the blame, though; if they stop selling unhealthy products, they may lose out to competitors. Without legally binding policies, there is no level playing field for companies ‘wanting to do the right thing’, and there is a huge amount of pressure to make profitable (less healthy) products for investors. Going forward, policies like taxes on unhealthy foods, tighter restrictions on the amounts of fat, salt, and sugar that products can contain, or limits on advertising junk foods (especially to children) could help.^{37, 38, 39}

All of this means that, even if we have some element of choice over what we eat, we simply can’t attribute all dietary-disease to individual willpower. Tackling dietary-related disease is a wicked problem that will require action on all levels – national, social, and within families – if we are to start turning back the tide.