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Obesity and its Causes
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Obesity in the 21st century and its Causes
Olli Lukkari discusses the obesity crisis, and its causes
Introduction
Obesity has become one of the fastest growing and most acute health threats of our times. At the start of the 21st century, an estimated 1.6 billion adults are overweight worldwide, with at least 400 million obese.[1] As a result, the health services, which are already under pressure, are stretched to their limits, as the rates of heart disease and diabetes are soaring. Medical experts are predicting that for the first time in 100 years, life expectancy in industrialised countries will fall.[2] With future predictions estimating the problem getting even worse, governments and international organisation across the globe have made dealing with obesity one of their health priorities.
Many studies have looked at the causes of obesity, and it is clear now that it is mainly due to changed lifestyles and diets.[3] People are eating more energy-dense processed food with more calories, exercising less and may not have the money or opportunity to buy healthy and nutritional food. Furthermore, aggressive advertising by the food producers, combined with a lack of public knowledge about food and nutrition makes the obesity epidemic extremely hard to tackle.
This article highlights the current obesity crisis by first looking at the concept of obesity and some historical trends. Secondly, it presents the prevalence rates and predictions, both in the UK and worldwide. Thirdly, it emphasises the causes by focusing on the shift in dietary patterns and changes in lifestyle, and deals with the economical and political aspects of obesity.
Measuring obesity and historical trends in obesity
Obesity can be defined in terms of body mass index (BMI), which compares a person’s weight with their height.[4] This gives a simple measurement on a scale ranging from 15 (starvation) to over 40 (morbidly obese), which is used to determine whether someone is within or outside a normal weight range. A person with a BMI over 25 is classed as overweight, while a BMI above 30 means obesity. The evidence shows, however, that the risk of chronic illnesses, such as heart disease, diabetes and some forms of cancer, ‘increases progressively from a BMI of 21′ [5].
Although BMI is widely used to measure overweight and obesity in the health service, and is the same for both sexes and adults of different ages, it is only a rough statistical guide. It does not take into account different body compositions, or the fact that muscle weighs more than fat tissue. Hence the BMI may overestimate obesity in people with heavy bones or an unusually high muscle density. Another problem with measuring obesity is that many studies are based on voluntary reporting, where people report their weight and height themselves. This can underestimate the prevalence of obesity, as people may underestimate their own weight.
Historically, in times of food shortages and malnutrition, being overweight was regarded as a sign of prosperity and wealth. When living conditions improved and the problem of accruing a decent nutritional intake was overcome, attention was turned to the health effects of obesity. Although obesity was first described hundreds of years ago, it was not until the early 20th century when first scientific studies on obesity were undertaken, and the link between obesity and an increased risk of death was discovered. [6] Since then, despite the increased knowledge and awareness of the adverse health effects of obesity, its prevalence has been increasing in both advanced market economies and less industrialised countries, surpassing some of the more traditional public health concerns such as infectious diseases.
Prevalence and predictions
According to recent estimates, there are now over 400 million obese people worldwide.[7] While the majority of them live in industrialised countries, mainly in Europe and North America, obesity and related illnesses are also a growing concern for less industrialised countries. For the first time there are parts of the world where, in a perverse way, obesity coexists with extreme hunger, adding to the burden of undernutrition and presenting a great challenge for local health services. Prevalence rates around the world have grown at an alarming rate in recent years. In the United States, which has the highest levels of obesity in the world, the number of obese adults has doubled since the 1980s, bringing the prevalence rate up to 30.4 per cent – meaning that about every third adult is obese. [8] In terms of adolescents and children, the levels are almost as alarming. Some 16 per cent of children aged 6-19 years are obese, putting them in a greater risk of becoming overweight in later years. [9]
In many European countries, obesity rates have also doubled in only a short period of time.[10] In 2002, at least half of the fifteen member countries had obesity levels above 20 per cent.[11] The UK has the highest growing obesity prevalence in Europe. Here, adult obesity has almost trebled since the 1980s.[12] The latest figures for England show that 22 per cent of men aged 16 and over are obese and 43 per cent overweight.[13] For women, the rates are 23 per cent and 33 per cent respectively.[14] That is over 4 million obese men and nearly 5 million obese women. Furthermore, obesity is becoming also increasingly common in younger people. Figures from 2003 show that over 1.4 million children in the UK are obese.[15]
The obesity epidemic shows little signs of slowing down in the near future. Globally, the World Health Organisation predicts that by 2015 more than 700 million people will be obese, an increase of 75 per cent. [16] Furthermore, obesity levels are soaring especially rapidly in low and middle income countries. In the UK, a report prepared for the Department of Health estimates that by 2010 there will be another 2.3 million obese men and 1.2 women, raising the total number of obese adults to roughly 12.5 million – more than a fifth of the whole population.[17] Among children, the prevalence among girls is predicted to grow by six per cent during this time, and will also grow significantly among boys, although at a slightly slower rate. Although these figures are necessarily only estimates, this report gives an idea of the scale of the problem, and helps to explain why obesity has quickly become a public health priority.
The causes of obesity
Overweight, and hence obesity, is caused simply by an energy imbalance – when someone consumes more calories than they use up. The excess energy is stored as body fat. While in some cases obesity can be a result of genetic inheritance, [18] scientists regard it to be mainly a consequence of changes in a person’s energy intake and energy consumption. In other words, due to changes in diet and physical exercise. In terms of diet, there has been a global shift towards more energy-dense food. These kinds of food, brought to us by developments in food processing during the last few decades, are different in the amount of calories and nutrients they contain. The industrialised diet is made up of the ‘wrong sorts of energy-dense food, saturated and processed fats, highly refined carbohydrates and sugars’, [19] including large amounts of “empty” calories – calories without any nutrients. A diet high in refined, energy-dense food may lack vital nutrients contained in unrefined food such as fresh fruit and vegetables, fish and nuts. Furthermore, processed food may undermine the way in which we control our appetite, as it does not fill us up naturally like unrefined food does.[20] We simply do not realise when we are full and keep on eating, needing more and more exercise to burn the extra calories, which are otherwise converted to fat.
Diet is not the only thing that has changed in recent history in industrialised countries. How we live, work, move around and spend our free time has been redefined by changes in our societies since the Second World War. Economic prosperity and technological innovations, many designed to make our lives better, may also have unexpected consequences. There has been a strong trend towards a decline in physical activity ‘due to the increasingly sedentary nature of many forms of work, changing modes of transportation, and increasing urbanisation’. [21]
Agricultural production, for instance, by nature an occupation that requires physical activity, employs less and less people. Between 1950 and 2000, the proportion of the population working in agriculture fell from almost 30 per cent to merely 4 per cent [22]. As office work becomes the main type of work in countries such as the UK, daily energy expenditure falls. This will result in weight gain unless compensated for, for example by increased physical exercise outside working hours. The use of cars and public transport is easier and more appealing than walking and cycling, especially when living in crowded cities. While there are situations where it is necessary to drive, statistics show that half the car trips in Europe now cover a distance less than five kilometres [23].
There are also economic and political factors contributing to the obesity crisis. Many of the primary causes for obesity, too little exercise and too much processed food, are a direct result of our improved prosperity. In short, ‘people use extra income to eat more and be less active’ [24]. Advertising may encourage people to consume ‘aggressively marketed foods that are high in energy but low in nutritional value’ [25] and products such as ‘cars, television sets and computers that promote sedentary behaviour’ [26].The food industry claims that obesity ‘would not be tackled by restricting freedom of choice’ [27]
However, it is clear that in order to really tackle this epidemic, more is needed than expecting individuals alone to make different choices about their diets and lifestyles. Ironically, it can be difficult for governments to come up with regulations which work in practise, and sound nutritional advice. Food is a big and profitable business, and the food lobby will of course try to prevent changes being imposed by governments. [28]
Conclusion
Health experts across the globe agree that obesity is fast becoming the main health threat in all but the poorest countries. At the turn of the century, millions of people are obese and billions overweight, with many countries having a third of their adult population classed as obese. Although we are yet to fully understand the causes of it, obesity is strongly linked to changed diets and lifestyles. Tackling this crisis will require action at many levels, and may be hindered due to lobbying by those with vested interests and a lack of true political will.
References
[1] World Health Organisation (2006) Obesity and overweight. Fact sheet No. 311
[2] Lawrence, F. (2004) Not on the label. Peguin: London.
[3] Lobstein T., Millstone E. (2007) Context for the PorGrow study: Europe’s obesity crisis. Obesity Reviews 8 (Suppl. 2), 7-16.
[4] ‘BMI is a simple index of weight-for-height that is commonly used to classify underweight, overweight and obesity in adults. It is defined as the weight in kilograms divided by the square of the height in metres (kg/m2).’ World Health Organisation. Global Database on Body Mass Index. http://www.who.int/bmi/index.jsp (accessed in August 2007)
[5] WHO (2006)
[6] World Health Organisation (2000) Obesity: Preventing and managing the global epidemic. WHO Technical Report 894. WHO, Geneva.
[7] WHO (2006)
[8] Baskin M. L., Ard, J. and Allison D. B. (2005) Prevalence of obesity in the United States. Obesity Reviews 6, 5-7.
[9] US Department of Health and Human Services (2001). The Surgeon General’s call to action to prevent and decrease overweight and obesity. US Department of Health and Human Services, Public Health Service: Rockville.
[10] International Obesity TaskForce and European Association for the Study of Obesity (2002) Obesity in Europe. The case for action. IOTF, London.
[11] Fry, J. and Finley, W. (2005) The prevalence and costs of obesity in the EU. Proceedings of the Nutrition Society, 64, 359–362
[12] Rennie, K. L. and Jebb, S. A. (2005) Prevalence of obesity in Great Britain. Obesity Reviews 6, 11-12.
[13] Zaninotto, P. et al. (2006) Forecasting Obesity to 2010. National Centre for Social Research, Department of Epidemiology and Public Health at the Royal Free and University College Medical School.
[14] Zaninotto (2006)
[15] Zaninotto (2006)
[16] WHO (2006)
[17] Zaninotto (2006)
[18] Farooqi, I. S. and O’Rahilly, S. (2007) Genetic factors in human obesity. Obesity Review 8 (Suppl. 1), 37–40
[19] Lawrence (2004), 208.
[20] Prentice, A. M. and Jebb, S. A. (2003) Fast foods, energy density and obesity: a possible mechanistic link. Obesity Reviews 4, 187-194.
[21] WHO (2006)
[22] Food and Agricultural Organisation, quoted in Lobstein and Millstone (2007)
[23] Lobstein and Millstone (2007)
[24] Nestle, M. (2003) The ironic politics of obesity. Science, vol. 299,
[25] Nestle (2003), 781.
[26] Nestle (2003), 781.
[27] Lawrence (2003), 223.
[28] Nestle (2003)
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