The deadliest diet in the world

Millions of adults worldwide are suffering from a virulent strain of diabetes, which can cause obesity and even kill. Are Western foods to blame?

The people of the island republic of Nauru, in the Pacific Ocean, are the living embodiment of what happens when a Western diet meets Eastern genes. A century ago, they lived by hunting and fishing and, although poor by Western standards, they were healthy, and nobody went hungry. Today, they are experiencing an epidemic of type 2 diabetes, which is marked by chronic ill health and obesity.

It all began in the 1900s, when the inhabitants of the tropical paradise discovered a rich seam of phosphate, the raw ingredient of fertiliser. Almost overnight they became very rich and were able to buy practically anything they wanted, including a carbohydrate-rich Western diet.

The trouble was, their genes were not built to cope with this new-found calorie wealth. The genetic predisposition meant that half the population now suffer from type 2 diabetes, which occurs when the hormone insulin no longer functions in its role of maintaining the correct sugar balance in the bloodstream. Being grossly overweight is the result.

But it is not just the Nauru islanders who have experienced the epidemic. Type 2 diabetes is rising at an alarming rate in many other regions of the world, where it has become one of the most important causes of ill health. It is a disease that has become synonymous with economic development and westernisation. Certain Asian populations are particularly susceptible.

Most people have heard of type 1 diabetes, which is caused by the cells of the pancreas producing too little insulin. Without insulin the body cannot use glucose, the sugar derived from food, nor can the liver process it. A person suffering from diabetes literally wastes away, unable to absorb any nourishment. Fortunately, injecting insulin after eating can counteract the worst effects of diabetes.

This form of diabetes is usually apparent from early childhood. In contrast, type 2 diabetes is associated with later life, and usually manifests itself in middle age. Sufferers fail to produce enough insulin but they also develop resistance to the hormone, making it quite ineffective. As a result, insulin injections fail to provide any benefit.

It is estimated that about 150 million people have type 2 diabetes. In Europe about 22.5 million adults, 5 per cent of the population, have the disease. The incidence is even higher in other areas of the world and is rising at an alarming rate. The World Health Organisation estimates that by 2025 there will be at least 300 million sufferers worldwide. The cost is astronomical: in Europe and the US, 10-15 per cent of total healthcare expenditure goes on type 2 diabetes and its associated complications; in the UK this amounts to £2bn a year.

Until recently, type 2 diabetes only affected older people who had adopted a Western diet but now evidence has emerged that younger people are also becoming susceptible. This year, eight European children between the ages of nine and 16 were diagnosed with the disorder.

Type 2 diabetics have high blood pressure and high LDL (low density lipoprotein) cholesterol. They run the risk of blindness, losing a limb due to nerve damage, kidney damage, and cardiovascular disease. Four out of five people with type 2 die of a stroke or a heart attack; their life expectancy is 10-15 years lower than those without diabetes.

"There is no such thing as mild diabetes," says Professor Eberhard Standl, executive chairman of the Diabetes Research Institute in Munich. "Type 2 is a killer."

The problem is that these symptoms are usually the only way to diagnose type 2 diabetes. It's thought that by the time a person is diagnosed by one of their symptoms they will have had type 2 diabetes for up to 12 years. Diabetes is detected by measuring glucose in the blood after fasting – first thing in the morning, for instance. But with type 2 diabetes, this figure could be normal.

The problem is that the beta cells in the pancreas, which normally produce insulin, malfunction. Fat is toxic to beta cells so the more overweight a person is, the more the cells are disabled. It's thought that as a person grows fatter, the body fails to produce enough insulin to cope with their increased bulk and raised levels of glucose in the blood.

New research has shown that prior to the onset of type 2 diabetes, sufferers are affected by a condition known as impaired glucose tolerance, or IGT. This is an impaired ability to deal with glucose, basically carbohydrates in the diet. Blood sugar rises very quickly after a meal, more so than it would in normal people but less so than those with type 2. However, it will return to normal or a moderately raised level.

There has been considerable controversy over how IGT can be diagnosed, but the consensus seems to be that it can only be diagnosed if a person's fasting glucose levels found in the blood fall somewhere between normal and diabetic levels.

IGT is the result of impaired insulin secretion, through insulin resistance – when the body no longer responds to the hormone. It usually occurs as the disease develops into fully blown type 2 diabetes. A study called Decode (Diabetes Epidemiology: Collaborative Analysis of Diagnostic Criteria in Europe) which was completed in 1999 analysed 25,000 people and showed that people with IGT were 50-per-cent more likely to die than those with a normal glucose tolerance. In a survey of almost 3,000 adults carried out in America, 15 per cent of them had IGT.

The cause, says Professor Pierre Lefèbvre, Emeritus Professor of Medicine at the University of Liège in Belgium, is our ageing population, an unhealthy diet, a sedentary lifestyle, the fact that unhealthy food is frequently cheaper, and a rise in levels of obesity. "It's the result of Coca-Cola colonisation, acculturation, modernisation and westernisation," he says.

There is also a genetic component to the disease. The highest rates of diabetes are found in Asian countries. The European children recently found to be suffering from type 2 are of Indian, Pakistani or Middle Eastern descent. In Europe, type 2 usually begins between the ages of 50 and 60; in India onset typically occurs between 35 and 45. IGT is also more common among some ethnic groups, for instance 20 per cent of Mexican-Americans have it as opposed to 15 per cent of white Americans. No one knows why.

Diabetes is partially influenced by genes. Some scientists have called them the "thrifty" genes, which have enabled human metabolism to cope with regular periods of starvation. "We are dealing with genes that have been in the genome for a very long time," says Professor Harry Keen, Emeritus Professor and consultant physician at the University of London's faculty of medicine. "They've been useful to us, they've kept us alive in periods of famine. Now a large number of people are getting enough to eat and those genes are deleterious. We're not going to find a single abnormal gene. My guess is that [in trying to discover the cause of IGT] we'll find a constellation of genes which will differ from family to family."

So what can be done about it? In one recent experiment, ten Australian aborigines were persuaded to revert to their traditional lifestyle. Within seven weeks their blood glucose levels had dropped from diabetic levels and they'd lost 8kg. Professor Lefèbvre says, "We don't have to go back to the bush, but we do need to adopt a similar lifestyle."

Professor George Alberti, President of the International Diabetes Federation, and Professor of metabolic medicine at Imperial College, London, has worked with a community in rural Tanzania where 90 per cent of the population suffered from diabetes. By persuading them to diet and exercise, he reduced the number of diabetics by half. The reason he believes his study worked, though, is because the tribal leader had diabetes himself so was very much in favour of the programme.

A study published last month in the New England Journal of Medicine conducted in Finland showed that individuals who had exercised and dieted for six years achieved a 60-per-cent reduction in the risk of diabetes. Professor Keen says that the participants in the Finnish study lost 4.5kg on average, but the loss of just one kilogram was enough to reduce their risk.

Also, drugs are becoming available to combat the disorder. Nateglimide increases insulin secretion and valsartan reduces insulin resistance. In 2002, the diabetes prevention programme will have completed its analysis of the effects of a change in lifestyle compared with taking the drug metaformin which increases the liver's sensitivity to insulin.

But Professor Keen warns that these drugs have side-effects. "It won't change insulin resistance or sensitivity," says Professor Alberti, "but the 'cure' for 90 per cent of type 2 diabetics is to keep a normal weight and exercise."

The experiences of the Nauru islanders should be a warning to all of us living in a more prosperous age. As Professor Keen says: "Eat less and walk more."