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What are the key causes of obesity?

One in ten adults in the UK is obese

The causes of obesity are many and varied but they all boil down one thing; taking in more energy in food and drink than you use up in daily activities. This means that the only way to avoid obesity and to maintain a normal healthy weight throughout life is to eat less but move more. This is, however, easier said than done.


As people in industrialised societies have moved from an active lifestyle in which they did regular, hard and physical work to having more sedentary occupations, their energy needs have reduced. But that does not mean that we necessarily eat less – in fact, increased consumption of highly processed foods rich in fat and sugar that make up fast foods, ready meals and convenience foods means that our energy intake has risen. This imbalance is one of the fundamental causes of obesity.


Of course, why the imbalance arises is very complex; the underlying causes of obesity are due to many different factors, some cultural, some genetic and some behavioural.

Cultural causes of obesity

Most human cultures put food at the centre of their social interactions. Groups and families from all different parts of the world gather together to eat meals, whether it is a royal banquet for 300 people, a ritual tribal feast or a small family breakfast. Eating and sharing food is a pleasure and can help maintain and strengthen the bonds that hold relationships together. Research has shown that this type of communal eating is a very positive experience and, interestingly, people generally eat much less in a group then they do when eating alone. The cultural causes of obesity stem from activities within human societies that use food for some other purpose.


One of the major causes of obesity, particularly in women in our society, is comfort eating. We become dependent on food as something to improve mood and as a way of coping with problems. Once the link between food and hunger is replaced by an association between food and feeling OK, whether you are hungry or not, eating can spiral out of control.


The fact that food is big business in the western world is another of the major cultural causes of obesity. In the Britain of the 1940s, there was very little choice of food. Fresh meat, vegetables, flour, sugar, eggs, cheese, some cereals, fresh fruit and vegetables made up the vast majority of everyone’s diet and there were hardly any convenience foods. The overall diet that people ate was generally very healthy although this was regarded as a time of austerity and some people undoubtedly did not have enough food.


Studies show that people tend to eat less when fewer foods are available but today, with supermarkets stacked high with thousands of different products, we have a much wider choice and we tend to eat more of a greater variety of foods. This hasn’t made our diet more balanced in the nutritional sense because it is now higher in fat and sugar and lower in the fresh foods that provide vitamins and minerals. Some experts believe that this greater variety could be one of the more subtle causes of obesity; it over-stimulates our palate, encouraging us to over-eat on a daily basis.

Genetic causes of obesity

Several key genes have been implicated as genetic causes of obesity but taking a more overall perspective, it should be no surprise that humans face such a battle with maintaining a sensible weight in modern society. Humans have evolved to be hunters and gatherers. We originally spent a lot of energy obtaining an unpredictable supply of just enough food to survive. The human system is geared up to feast in times of plenty to store up fat to survive the leaner periods when food is scarce. In an environment where there is always plenty of food, the body’s natural reflex is still to eat in case the supply runs out. Our evolution could be one of the key causes of obesity that will be very difficult to overcome.


The specific genetic information certainly paints a very complex picture. Some people have a mix of genes that makes them more likely to become obese but other people seem to have no apparently abnormal genes but they become exceptionally obese. Some mixtures of genes may cause people to metabolise food differently, or genetics may make a difference to the way they feel hunger or, more importantly, the way they feel full after eating. More studies may eventually unravel the complex processes involved and may pinpoint the exact genetic causes of obesity. Research may also lead to better treatments for extreme forms of obesity in the future.

Behavioural causes of obesity

With genetics and culture already tending to make us overeat and gain weight, our behaviour can tip us over the edge. If we choose to buy high energy foods and opt to do as little exercise as possible, obesity is almost inevitable.


The behaviour that we choose is often a result of our parents and our friends and peers. People whose parents are obese have a much greater chance of becoming overweight themselves. The culture of binge drinking and regular drinking in the UK is also one of the major behavioural causes of obesity. Alcohol has to be broken down by the liver and, although it contains a lot of calories, it has few nutrients. Drinking large amounts on a regular basis adds to the imbalance between energy intake and the energy used up.


Stress, pressure at work, giving up smoking can all make comfort eating more likely and feeling depressed or having low self esteem also makes people feel less able to take part in sports or other activities that involved physical exercise. Taking too little exercise, even if you eat sensibly, is another of the major behavioural causes of obesity.

Tackling the causes of obesity

Many medical experts and people in government realise that obesity is a major threat to the health of the population in general. Obesity can lead to a far higher risk of major chronic and potentially fatal diseases such as heart disease, strokes, diabetes, some types of cancer and arthritis.


It is much more difficult to know exactly how to approach the causes of obesity to make a radical difference for the future. Better education is one method and schools are putting in place many different programs to encourage children to start eating more healthy food and to learn to love doing exercise and sport – but doing enough to combat all the different causes of obesity is likely to be a great uphill struggle.

Kathryn Senior

Profile of the author

Dr Kathryn Senior is an acclaimed medical journalist who has written over 500 feature articles for leading international journals within The Lancet group. As Senior Writer at Freelance Copy she produces high quality scientific and medical content for websites and printed publications for companies and organisations in the health, medical and pharmaceutical sectors.