At a fundamental level, weight gain arises from an energy imbalance. Some weight gain is expected in certain populations, but why do we see runaway obesity statistics across the globe, including developed cities and regions such as Hong Kong and Singapore?

It is a common misconception that only industrialised nations have this problem; however, many developing countries are now seeing dramatic increases in the rates of obesity. What was once a problem of the wealthy is now a global phenomenon that impacts all societies and social classes. But what is causing it? There are many misconceptions around obesity, including demonising food groups and blaming the individual for their condition. The reality is that obesity is a far more complex condition than most people realise, so I’ll try to highlight some of the key issues below.

There is simply more food available to us

Part of the problem of obesity is that there are simply more calories available to us than ever before. Over the past 50 years, the average availability of calories to each human has risen from around 2200kcal in the 1960s to 2800kcal in 2013. Therefore, on average, energy consumption as increased, contributing to the energy imbalance needed for weight gain.

Portion sizes have increased

There is evidence that portion sizes in restaurants and packaging sizes of many foods have increased over the last 30 years. This is, in part, reflected by where we eat food. Between 1977 and 1991, there was a 75% increase in the number of restaurants in the US, the majority being fast-food restaurants that offer low-cost meals and large portion sizes. Our modern food environment is partly to blame here. If you take a walk down any high street in any developed or moderately developed nation, what is there an abundance of? Food! These days it is so much easier to get a highly palatable, low-cost, delicious meal at a restaurant or have it delivered to your doorstep with little to no energy cost. Combine that with people working longer hours, less willpower (or even knowledge on how) to cook, then you end up with a restaurant culture with families eating out multiple times per week.

Increasingly sedentary lifestyles

As more and more of the world’s population shift from an agrarian to an industrialised society, which comes with all the creature comforts that we are accustomed to, we are spending more time in environments that require less and less physical activity. Worksites, schools, homes, and public spaces have been re-engineered to minimise human movement and muscular activity. These changes have a dual effect on human behaviour: people move less and sit more, which our energy expenditure and, thus, calorie balance.

Sociodemographic impact

Many people want to blame the individual for weight gain and obesity without considering the sociodemographic factors that might apply to them. A person’s income, poverty level, social status, employment status and education level all play a part in the health outcomes of an individual, including obesity. For example, vegetarians and vegans (supposed health-promoting dietary patterns) are far more likely to be educated to university level. It has also been shown that you can get more junk food calories for your money than healthier alternatives. If you are struggling to make ends meet and have a family to feed, it makes sense to stretch your money as far as possible. Another barrier to eating more fresh food can be the perishability of the food. Everyone knows that a piece of broccoli is probably better for them than a frozen French fry, but what if they lack the knowledge of how to prepare the broccoli in a way that is acceptable to their families so that it actually gets eaten? What if you don’t even have a fridge to keep the broccoli in so that it doesn’t perish before it gets eaten?

These are real problems that people have and, in this situation, the safer bet (in terms of being able to feed their family) might just be to have the French fries in the freezer, where they won’t perish and will definitely be eaten. Some families living in poverty live in a ‘food desert’ where there are 5 fast-food restaurants for every supermarket. If you have to take 3 buses to get to the nearest place that sells fresh food and you already work 2/3 jobs, what’s the likelihood of you being able to do that?

Increased exposure to food cues

In most industrialised nations and urbanised populations of the modern world, there is an onslaught of advertisements for enticing foods (food porn) in the public space and at home through digital media, whose sole purpose is to make you buy and consume more food. These signals are mainly processed unconsciously, meaning they are relatively impervious to conscious control. In 1997 in the US, the food industry spent around $3 BILLION on convenience food, confectionery, snacks, and soft drinks compared with just $159 million for fruits, vegetables, grains, and beans. It’s probably no coincidence that seeing an advert for a Krispy Kreme doughnut rather than an apple on the way to work might make you want one at lunchtime or on the way home from work! This challenges our ability to regulate our body weight.

Genetics

Genes give our bodies instructions for responding to changes in the environment. There are variations in genes between obese and non-obese individuals that could influence behaviour (drive to overeat or tendency to be sedentary) or metabolism (such as low capacity to use fats for fuel or an increased tendency to store body fat). However, only about 20% of BMI variation can be accounted for by common genetic differences between individuals, meaning that there is a lot more still at play. Obesity is probably the result of complex interactions between genetics and environmental factors that remain poorly understood.

Obesity is a complex problem

Obesity is a complex issue with deep psychological roots, and that requires a fundamental change of diet, lifestyle, and environment. However, how exactly this can be achieved is a puzzle that needs to be solved. At an individual level, it is easy to tell people to eat less and move more, but we know after decades of trying that this doesn’t work. With our current food environment and powerful food lobbying associations resisting the taxation and reduction of high sugar/fat/salt foods, I believe the odds are stacked against us.

What is causing the obesity epidemic?