BY DR JANE OGDEN, PROFESSOR IN HEALTH PSYCHOLOGY
Obesity is clearly on the increase and has many physical and psychological consequences. This paper will describe definitions of obesity, its impact on health and its causes with a focus on genetics, the obesogenic environment and the role of behaviour.
What is overweight?
The easiest way is to calculate whether someone is overweight or obese is to use Body Mass Index (BMI) which is a ratio between height and weight and can be calculated using any online BMI calculator. This produces a number as follows: normal weight: 18-24.9; overweight: 25-29.9; Obese: 30+. Since the 1980’s adults and children have become heavier in most countries of the world. The highest rates of obesity are found in Mexico, Tunisia, the USA, Saudi Arabia and Canada, and the lowest are found in China, Mali, Japan, Sweden and Brazil; the UK, Australia and New Zealand are all placed in the middle of the range. Across Europe people in Northern and Western Europe are thinner than Eastern and Southern Europe and women are more likely to be obese than men.
The consequences of being overweight
Obesity has several consequences and can cause both psychological and physical health problems. In particular, being obese is associated with body dissatisfaction, low self esteem, anxiety, low mood and a general lack of confidence. It also increases the chances of cardiovascular disease, heart attacks, diabetes, joint trauma, back pain, many types of cancer, hypertension and strokes and the likelihood of these problems simply increases as a person’s BMI gets greater than 25. Obesity is also directly linked with mortality and decreased life expectancy.
The causes of being overweight
So what causes this problem? There are three key approaches to understanding the causes of weight gain which focus on genetics, the environment and behaviour.
Body size runs in families and the probability that a child will be overweight is related to the parents’ weight. Parents and children, however, share both their environment and genetics so this likeness could be due to either factor. To address this problem, research has examined twins and adoptees. In general, researchers believe that there is a role for genetics for both weight and where body fat is stored (upper versus lower body), that a mother’s weight is a better predictor of her child’s weight than that of the father and that the role of genetics gets less as a person’s BMI gets larger. BUT this cannot explain why there has been such a huge increase in the prevalence of obesity over the past 30 years as our genes have not changed during this time. Nor can it explain the compelling evidence which comes from migration data which shows that as populations move from one country to the next they quickly take on the body weight of their new environment. Finally genetics cannot explain how obesity seems to be contagious within friendship groups. Researchers have therefore turned to both the environment and individual behaviour as more useful explanations.
The obesogenic environment
To explain the increase in obesity, researchers have turned their attention to the role of the external world which has been labelled an ‘obesogenic environment’. For example, the food industry with its food advertising, cheap ready meals and take aways discourages food shopping and cooking and encourages eating out and snacking. There has also been a reduction in manual labour and an increase in the use of cars, computers and television which makes us more sedentary at both work and home. This obesogenic environment creates a world in which it is easy to gain weight and requires effort to remain thin. However, not everyone in this environment becomes overweight which points to a role for behaviour. Particularly what we eat and how active we are.
The role of behaviour
The energy in versus energy out equation is a very fine balance and even just eating one extra piece of toast per day, that you don’t need, can result in a half stone increase in weight after a year. It is clear, therefore, that people who are overweight have eaten more than they needed in the past. It is also clear that in order to maintain this level of weight they must be eating exactly what they are using up in energy otherwise their weight would go down. Eating behaviour and activity are therefore key to weight gain.
At its simplest eating can be seen as the result on what’s in our heads and the triggers in our environment which in turn can lead to overeating.
What’s in our heads
From the moment we are born, we learn to like certain foods in the same way that we learn to speak, to like certain clothes or to enjoy certain hobbies. And this can cause overeating which can be seen in terms of the following factors.
When a child is upset the easiest and quickest way to calm them down is to give them food. In the longer term this can be harmful as we quickly learn that food is a good way to manage emotions. Then as we go through life whenever we fed up, anxious or even just bored we turn to food to make ourselves feel better. This is known as emotional eating and is linked with weight gain.
Food is also central to the way we socialise with others and for many this leads to overeating and subsequent weight gain.
Food also plays a central role in the way that we see ourselves and a core part of our identity. Food can therefore become a language to speak with and as a result can result in eating more than we need and becoming overweight.
Guilt and denial:
For many, food is linked with denial which can’t last long as people end up eating and swing between eating, guilt about eating and then subsequent overeating and a means to manage the guilt. This in turn can lead to weight gain.
Food and reward:
Eating food is rewarding as it tastes nice and makes us feel good. Food is also used as a reward for when we deserve a treat, a break from work or have met one of our goals. And these rewards are often in the here and now whereas any costs are in the future as cake now always beats heart attack in 40 years. So we overeat and our weight goes up.
Triggers in our environment
Eating is also a response to triggers in our environment and the obesogenic environment makes it very easy to eat and offers a wide range of triggers which causes mindless eating and changes what, when, where and why we eat.
We now live in a world where portion sizes are bigger, cakes are offered around at work, we have snacks in our cupboards and ‘drive in’ fast food restaurants where we can buy thousands of calories worth of food without even having to stop driving to eat it. And we eat it because it’s there.
What we eat:
With the decrease in cooking from scratch and the increase in fast food outlets, takeaways and ready meals the obesogenic environment has changed what we eat. This causes weight gain as fast foods, takeaways and ready meals and often very high in fat.
When we eat:
The obesogenic environment also means that we are far more likely to eat snacks than meals and unfortunately, snacks are often higher in fat and calories and more likely to be forgotten or discounted. This means that snacking makes people eat more in the longer term as they have not registered that they have eaten and therefore don’t feel as full.
Where we eat:
There have also been changes to where people eat and not only do people eat more snacks but they eat these snacks on the go either in the car, at our desks or in the street. An eating on the go makes people less full so they eat more later on.
Why we eat:
We eat for many reasons other than hunger as food is used a way to manage our emotions, for social interaction, to make statements of our identity; all the factors that are in our heads. The environment around us not only changes when, where, what and how we eat it also changes why we eat and it also acts as a trigger for these different reasons. And this all makes us overeat and gain weight.
Obesity is also related to a second behaviour – being active. And similar to eating behaviour, being active can also be understood in terms of what is in our heads and the triggers in the environment.
What’s in our heads
Exercise is good for our physical and mental health. But knowing this is not enough to make us more active. Actually doing exercise is related to the way in which we think as follows.
Exercise is far more likely to happen if it is a social activity which brings with it social benefits. Not recognizing or valuing the social benefits of exercise may lead to people becoming inactive which in turn can prompt weight gain.
Exercise also reflects whether being active is the norm in someone’s family or social group. So if you change job and make new friends who are all quite active, the chances are you will become more active as well. Similarly, if you meet a group of people who enjoy sitting around eating cake and drinking tea then you may well start to gain weight. Such social norms therefore influence how active people become.
Exercise is fun:
Most exercise campaigns emphasise health benefits and tell people that keeping active is good for your heart, helps you live longer and helps you to maintain a healthy weight. But most of this means very little to most people who live in the present and find it hard to worry about having a heart attack when they are 65. Therefore, the next main reason why people exercise is having fun. If exercise is fun, the benefits of doing it NOW easily outweigh the costs, and it works by making the here and now more enjoyable.
The impact of exercise on mood:
Exercise is good for our mood. Once people have felt the psychological benefits of exercise, they will start to believe that being active benefits them and will therefore will do more of it.
Feeling confident is also key to being active. The best way to build confidence is simply to do something a few times, congratulate yourself on having done it and then do it more.
The perceived costs of exercise:
There are many costs that get in the way of exercise such as ‘it’s time consuming’, ‘it’s boring’, ‘it takes time’, I’m busy’, ‘I don’t like getting sweaty’, ’I don’t like having to change’, ‘it’s embarrassing as I’m not very fit’ and ‘it costs too much to join a gym’. Exercise will be more likely to happen if it is done in a way that avoids all these costs.
Triggers in the environment
Being active and carrying our exercise is also a response to triggers in the environment.
Being active requires green spaces, pavements, cycle paths, stairs, gyms, sports facilities and playgrounds. Simply having access to these facilities makes it much more likely someone will be active.
Cost and time:
High prices, difficult to reach facilities and busy lives can provide a barrier to becoming more active.
Part of daily life:
The main reason for being active is that it is ‘just part of my life’. Accordingly, an environment which makes it easier to incorporate activity into everyone’s daily life will be more likely to trigger more active lifestyles.
Any behaviour is a simple cost / benefit analysis and at the time of doing anything the benefits will outweigh the costs. Further, people are very good at future discounting which means the present outweighs the future. For eating and exercise this is problematic as cake now (and sitting now) will always beat heart attack in 20 years time. The trick is therefore to find the more immediate benefits of behaving in a healthy way and the immediate costs of not doing!
Overweight and obesity have increased dramatically over the past 30 years and impact on both physical and psychological health. Although there is a role for genetics in weight gain, there is a stronger role for the environment and our behaviour. This paper has described how eating behaviour and activity are clearly linked to obesity and a product of what’s in our heads and triggers in the environment.
Ogden, J. (2018) The Psychology of Dieting. Routledge: London.