Obesity

'For the first time in history, the world's total of overweight people equals the total of those who are underfed. Up to 1.2bn people eat more than they need, and as many go hungry each day.' (The Guardian, March 2000).

It is estimated that more than half the British population and two thirds of the American population are overweight or obese. The past twenty years has also seen a dramatic increase in childhood obesity with twice as many American children and three times as many adolescents being overweight now compared with 1980. Obesity is the second leading killer of Americans, beaten only by cigarette smoking. What is the reason for such a dramatic increase in this epidemic?

Consider one of the most severe cases of obesity in Britain, that of Barry Austin. Barry was obsessed with eating, saying that food was his god and he worshipped it. He weighed 318kg at the age of 29 and clearly consumed more food than his body required or was able to burn. Typically, for breakfast Barry would eat four packets of crisps and half a box of biscuits. After lunch, from the chip shop, he ate several plates of beans on toast, fruit-cakes and more crisps. For tea he would have 6 lamb chops, 12 roast potatoes, vegetables and gravy, pie and custard. Finally for supper he had five large hamburgers. This was all washed down with 12 litres of cola each day. Can today's society really feel sorry for someone like Barry? Is he simply another obesity case who practices two of the deadly sins, greed and gluttony? Or is it something he cannot help and should certainly not be 'blamed' for?

Obesity is a disease and it can lead to heart disease, diabetes and an increased risk of cancer. More than a quarter of cancer cases worldwide are related to being overweight, while over three-quarters of sufferers of type II diabetes are also obese. Type II diabetes is the form of diabetes that usually occurs in adults. Sufferers develop a resistance to their own insulin and become unable to regulate the sugar levels in their blood. However, in recent years this previously adult-only disease is being diagnosed increasingly in teenagers and even in children. Some experts insist that it's not just how much fat you have but where you carry it that affects your risk of developing other diseases. Men and post-menopausal women have an "apple-shaped" distribution of fat, carrying it predominantly inside the abdomen. Pre-menopausal women tend to have a "pear-shaped" distribution, with flab on the thighs and buttocks. "Apples" carry a higher risk of developing heart disease and diabetes than do "pears".

There is a paradox here. How can nations like America and Britain that are so body-obsessed become so overweight? Over the past 20 years the media, bookshelves and TV programmes have been filled with the notion of healthy eating, pro-carbohydrate, pro-fibre, low fat, no cholesterol, no sugar foods and diets. Supermarket and food chains have participated in this consumer hype and developed so called 'healthy eating' options. Many people are devotees of 'weird and wonderful' fitness regimes; Yoga, Pilates, Spinning, Body Pump, Tae-Bo, Boxercise, just to name a few. But despite being encouraged to get fitter, the population as a whole has instead got fatter by the year. One simple reason for this is that our lifestyles have changed such that the majority of people live more sedentary lives. The price we pay in all age groups is a sharp increase in obesity.

In our society there is no longer a need to search for food and water. You only have to walk through any town centre and you will be offered an array of inexpensive and convenient fast food restaurants. It is no coincidence that the rapid increase in obesity has accompanied a rapid increase in the number of fast food chains. Dining out is more common and eating food is seen as a means of entertainment, often accompanied by alcohol. With greater variety and more social eating people may tend to gorge more and drink more alcohol leading to larger and unhealthier individuals. Why is this? Have we lost the will to stop eating when food is plentiful? People are busier than ever so they grab whatever is quick and convenient. Unfortunately "quick and convenient" does not necessarily mean "nutritious and healthy". But this is a poor excuse considering that most supermarket aisles are well-supplied with fresh vegetables and salads that require no washing, no cutting - just eating!

It is thought that the greatest contributory factor to 'childhood' obesity is diminished physical activity. Gone are the days when children played outside until dusk and walked to and from school. After-school and holiday activities often consist of playing computer games, watching television and surfing the Internet, but these do not burn off many calories. Television also adds to the temptation: the average American child apparently sees 27,000 food advertisements on television every year!

Some people can maintain a normal body weight despite overeating. Changes in feeding behaviour do not always correlate with changes in bodyweight: it seems that some of us are predisposed to become obese. Studies of certain populations show that genetic factors certainly can have a role in obesity. Studies of identical twins and of families indicate that as much as 80% of the variation in body weight may be attributable to genetic factors. There are also diseases, caused by changes to a single gene, whose symptoms include obesity but these types of disorders are extremely rare and cannot account for the current 'epidemic' in obesity.

Animals and humans eat for a variety of reasons: hunger, time of day, social setting, stress, boredom, palatability/reward, and food availability. Some animals have evolved so that they are able to burn fewer or more calories depending on the circumstances of their life or changes in the weather. For example, the ability to store substantial amounts of energy in the form of fat allows dairy cows to achieve high rates of milk production. Hibernating animals also depend on the ability to reduce their energy expenditure while still maintaining the body processes necessary for life. Some hibernators are able to reduce their metabolic rate by 95%, which causes a drop in body temperature and enables the animal to survive during the winter. Humans possess many of the same genetic adaptations but they remain "dormant" since current lifestyles do not require such responses. The differences in these genes between individuals may explain some of the differences in bodyweight between people who otherwise seem to eat the same and exercise the same amount.

From an evolutionary perspective the ability

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