It is impossible to be sure what proportion of the western world is obese but current estimates suggest that about 30 per cent are ‘clinically’ overweight. That obesity increases one’s chances of suffering from diabetes, heart attacks, gall-stones, hiatus hernia, cancers of all kinds, painful feet, arthritis of the hips and knees and several other conditions is now beyond dispute. It shortens life and reduces the quality of life for countless millions of people. Obviously obesity is a terrible health and social problem.
In the 1920s obesity was rare in African rural peoples and a 1960 study suggested that low body weights were lifelong in rural Zulu men. There is now overwhelming evidence that in certain ways the control mechanism of body weight somehow breaks down in an affluent society. Individuals in primitive societies have a kind of automatic regulator which controls the amount of effort they spend searching for food and the amount of food they consume. According to one world expert, ‘Supermarket Man has no such automatic facility.’
An adult man, wherever he lives and however he eats, who eats 1 per cent more energy every day than he expends accumulates 1 kg of fat per year. At 30 such a man would weigh 30 kg (66 lb) more than someone who had been in good energy balance for a lifetime. Obesity is a real hazard to hunter-gatherers because it slows them down, affecting their ability to catch prey and to escape animal predators. So in survival terms it pays the hunter-gatherer to keep slim. Such peoples get their food mainly from plants, and individuals spend 2-3 hours a day gathering food, three-quarters of which is supplied by women and children gathering and one quarter by men hunting. Many hunter-gatherers live long enough to become obese but they do not do so. In one study of such a group 7 per cent of the men were over 65 but they were all slim.
The first agricultural revolution, in about 10,000 BC, changed things radically for most of the world’s population as man began to farm cereals and to store food. The diet of today’s peasant agriculturalist has changed little since this time. Although food shortages occur in developing rural peasant communities, resulting mainly from population density and poor soil fertility, competent scientific observers say that even where the population is not dense, the soil is fertile and there are two harvests a year, body weight remains low throughout adult life.
Pastoral peoples plant no crops but raise animals and eat meat, blood and milk. Studies show that their blood cholesterol levels remain low despite the high intakes of animal fat and cholesterol, and that obesity is rare.
The second agricultural revolution started in Europe towards the end of the eighteenth century and crop rotation and fertilizers, together with better machinery and animal husbandry, changed western eating habits totally. The upper classes became wealthy; meat, butter and milk could be consumed throughout the year; and sugar intake went up, as did that of alcoholic drinks. Obesity suddenly became extremely common in the upper social classes, towards the end of the seventeenth century and even more so in the eighteenth century. Portraits of even quite young people of the time show double chins.
With the coming of the Industrial Revolution in the nineteenth century the production of goods and wealth really took off. This enabled radical changes in the production, storage and transport of food. Dietary fibre began to be milled out of bread-the staple diet of the masses. Salt, sugar and fat intakes rose and the consumption of starchy foods fell. Fruit and vegetable intakes rose steadily. People got less exercise, as machines began to do the work. Slowly food became so plentiful, even for the masses, that people began to eat snacks between meals as well as regular meals-themselves a luxury for many until 200 years before.
So why is obesity so common in the West and hardly ever seen in non-westernized peoples? The main answer is that our food has radically changed in character-it is not simply that we eat too much of it, as was previously thought. Over half the energy in the food of a hunter-gatherer or peasant agriculturalist comes from high-starch foods. Such a diet eaten even ‘to excess’ does not cause obesity, partly because it is almost impossible to eat an excess, so bulky and filling is it. At least two-thirds of the energy in a western diet comes from fibre-free fats and sugars and low-fibre cereal products. Undoubtedly, there are other factors in the production of obesity but, looking at populations overall, food is undoubtedly at the heart of the problem. That westernized people can slim by adopting a high-fibre (rich in unrefined carbohydrate) diet is no longer in doubt; and the observation that slim, rural dwellers in non-westernized countries can be made obese very quickly on a western diet is not easy to refute.
It seems that food intake stops when we feel we have had enough and that we feel satisfied sooner on foods rich in dietary fibre – i.e. unrefined carbohydrate foods. It is simply so easy to over-consume refined foods that have no appetite-controlling capacity that we in the West eat ourselves to obesity.