Authors: Jörg Blech
A GLOBAL EPIDEMIC
The epidemic of type 2 diabetes is a dire reminder that people today are genetically hardwired to pick berries and hunt mammoths. Two millions years ago, most hominids had a rather busy week. The men spent up to four days hunting; the women spent two to three days gathering food and other useful items. Physically demanding work was performed every day. Our forebears would carry their babies, kill and gut their prey, make stone tools, break bones open (to get the nutritious marrow), and build dwellings. Life was never boring and could change abruptly. In times when food was plentiful, people greedily devoured enormous portions of meat. During famine, however, they had so little food that they could starve to death.
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So, is modern civilization actually bad for us?
Of course not, and it doesn’t require deep thinking to find reasons. Mean life expectancy is increasing every year by another three months, a trend that has endured for more than 160 years, chiefly driven by enhanced hygiene and safer food. Infant mortality is lower than ever. Heated houses, sanitary facilities, and health-care services have reduced the risk of death from infections and injuries, which were the most frequent causes of mortality 200 years ago.
And yet there are signs indicating that life expectancy, contrary to the predictions of many demographers, is about to level off and might even decline. “Looking out the window, we see a threatening storm—obesity—that will, if unchecked, have a negative effect on life expectancy,” claims Jay Olshansky at the School of Public Health of the University of Illinois at Chicago, along with colleagues in an article in the
New England Journal of Medicine
.
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Unless obesity among Americans is reduced, “the youth of today may, on average, live less healthy and possibly even shorter lives than their parents.” A prognosis of the Department of Health in London arrives at a similarly grim prediction, stating that the mean life expectancy of Englishmen will be five years lower by the year 2050.
In the past, type 2 diabetes affected, if anyone, only people of old age. Today, the medical term “adult-onset diabetes” is outdated. One of every three children born in the United States in 2000 is going to suffer from type 2 diabetes at some point, often early in life. This will only add to the dramatic health disparities already existing in the United States. Women living in affluent neighborhoods of New Jersey have a mean life expectancy that is 30 years higher than that of women dwelling in parts of South Dakota.
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The gears of evolution grind slowly, making it impossible for our genetic makeup to adapt to the modern world. Today, the evolutionary program for energy conservation means that our muscle and bone tissues immediately begin to degrade as soon as we curl up on the sofa. If you don’t use it, you will lose it. The resulting obesity and metabolic changes fuel the diabetes epidemic.
For some creatures, however, idle time does not always lead to a rapid degradation of bodily structures. Black bears, for example, rest five to seven months during the winter and retain most of their strength. Upon leaving their dens in the spring, the bears are in good shape and eager for activity. After 130 days of dormancy, the muscle strength of a bear’s leg has declined by 23 percent, whereas a human leg would lose 90 percent of its power during the same period of rest. The difference lies in the genes. Black bears have evolved a metabolism suitable for hibernation. Certain biochemical mechanisms see to it that the bear’s muscular system is not wasting away in the den.
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We humans are wired in a different way. We need exercise, much as we need air for breathing. We’ve inherited bodies that depend upon regular moderate activity. However, it is also the excess supply of food that does not agree with us. Humans evolved in times when famines abounded. Thus, after overeating, the body is not going to flush away all these superfluous sodas, sundaes, and pizzas. Instead, it converts all these calories into padding of sheer fat.
Curiously, humans are not the sole creatures unable to say “no” in front of a full plate. Cats and dogs also lack an instinct that would stop them from overeating. The masters and their pets are in the same boat: apparently 20 percent of all cats and dogs in the United States are obese. They, too, are at risk of getting cancer, type 2 diabetes, and arthritis. And American veterinarians have noticed another remarkable fact: the obese pets frequently resemble their mistresses and masters. “We see large numbers of domesticated pets being fed very high quality food and living very sedentary lifestyles with very limited exercise,” says Scott Alan Brown at the University of Georgia in Athens. “Quite honestly, it’s analogous to what we see in the pet owners.”
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This excessive supply of sugar and fat has changed the constitution of a whole generation. This metamorphosis is especially evident when people gain access to unlimited food in a relatively short period of time. In West Germany, it happened shortly after the Second World War, when the first beer bellies popped up. Other researchers note the Pima Indians, a tribe whose people live in Mexico and the United States. Those in the United States consume 500 to 600 kilocalories a day more than their counterparts across the border. The result of this is that the Pima in the United States are on average 26 kilograms heavier and have one of the highest rates of type 2 diabetes in the world, some 50 percent of the population.
The onset of this metabolic disease is a textbook example of how much humans are still adapted to the Stone Age. The body is capable of storing only a small amount of sugar (glucose) in the liver and in the muscles. This supply becomes depleted after only one day of fasting. For this reason, the body needs a regulatory circuit protecting its glucose supply during a famine—which is why resting muscles are unable to fish glucose out of the bloodstream.
“Consequently, it would have been advantageous to our ancestors to develop a system that allowed only physically active muscles to remove blood glucose,” explains Frank Booth at the University of Missouri in Columbia.
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For the average American, who consumes fast food and drives everywhere, this ancient system now fires back. Underused muscles are not able to suck the glucose out of the bloodstream, and the blood then becomes thickened with sugar. This metabolic turmoil actually led to the name of the disease “diabetes mellitus” because those affected drink a lot of liquids and subsequently flush out unusually high amounts of urine (the term comes from the Greek
diabainein
, meaning “to flow through”). On the other hand, the urine contains high levels of sugar and is sweet; thus the term “mellitus” (derived from the Greek
meli
, or “honey”).
In reaction to the excess amounts of glucose molecules in the blood, the body starts to produce high amounts of the hormone insulin. It is made in the pancreas and helps the muscle cells filter glucose out of the blood. The high levels of insulin, however, have unintended consequences: the cells stop responding to the abundant glucose molecules, instead becoming resistant. Subsequently, the whole glucose metabolism spins out of control, and the affected person falls sick with type 2 diabetes.
The disease progresses incrementally, and in the beginning there are no symptoms that can be felt, with the possible exception of fatigue and thirst. Furthermore, some affected men lose interest in sex. These sexual problems are caused by diabetic changes in the blood vessels and by the resulting impairment of the blood circulation in the pelvis, but patients erroneously blame their age for their loss of potency.
Before the Second World War, a person suffering from type 2 diabetes was a medical curiosity. Only 0.4 percent of the German population suffered from adult-onset diabetes, as the condition was then known. Today, 10 percent of Germans are affected.
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In the United States, the figures are also skyrocketing: according to the National Institutes of Health, approximately 19 to 20 million Americans have type 2 diabetes, and about one-third of them don’t even know it. Diabetes prevalence in the United States has increased by 49 percent from 1990 to 2000 and is now believed to be the sixth leading cause of death in this country.
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Yet many patients regard type 2 diabetes as nothing but an annoying condition that could be easily managed and controlled. Ironically, medical advances have given rise to this popular fallacy. Canadian researchers discovered in 1921 that diabetes was caused by a lack of insulin. In the wake of this discovery, scientists found ways to produce insulin outside the human body that could be administered to patients. This treatment made it possible to keep even people in advanced stages of diabetes alive. Furthermore, pharmaceutical companies began producing so-called antidiabetic drugs. Although experts doubted the effectiveness of these products, their ready availability tricked patients into believing there was a quick fix for their problems. Additionally, manufacturers introduced expensive food products like diabetics’ chocolate, pudding, and marmalade. This created the illusion among diabetic people that they could lead a more or less normal life, as long as they consumed the many products from pharmaceutical and food companies.
Patients’ optimism, however, turned out to be premature. Many of the people who have simply rejected admonitions to exercise now have to face the dire consequences of their decisions. Even though people with type 2 diabetes can survive for a surprisingly long time, they don’t have a particularly enjoyable life. The long-term consequences of the disease are severe. For one, the circulation becomes weak, and the kidneys often stop working, making dialysis necessary. The high level of glucose in the blood can destroy the retina, a fatal degeneration causing blindness. Eye damage is thought to occur in 19 percent of diabetics.
Moreover, the sugar in the blood attacks nerve cells in the feet and in the legs. Problems such as amputation of a toe or a foot, foot lesions, and numbness in the feet occur in 23 percent of people with diabetes. And sadly, an amputation usually further worsens the lack of exercise that promoted the onset of type 2 diabetes in the first place.
EXERCISE TO TREAT DIABETES
Proof that physical activity is effective in treating diabetes is the outcome of a whole array of studies. In the Chinese city of Daqing, sedentary persons who already showed early symptoms of the disease were allowed to keep their drinking and eating habits, but only if they committed themselves to regular exercise. Six years later their risk for developing full-blown type 2 diabetes was cut by 46 percent. Individuals in a control group conversely stayed sedentary but changed their eating habits. They only reduced their risk by 31 percent.
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In one trial, 3,234 overweight Americans at the onset of type 2 diabetes (they had impaired glucose tolerance) were randomly divided into three different groups. The members of the first group were given a daily dose of the standard medication: two tablets of metformin to slow down the glucose production in the liver, thereby lowering the level of glucose in the blood. The patients of the second group received placebo pills. The members of the third group were encouraged to change their lifestyle: They were asked to go on a low-fat diet and to walk for 30 minutes, five days a week, with the goal of losing 7 percent of their body weight.
After three years, all the participants of the study were reexamined. In the group taking the standard medication, the prevalence of the disease in comparison with the group receiving placebo was reduced by 31 percent. However, the individuals prescribed the walking treatment were in better health, with the prevalence of the condition lowered by 58 percent.
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Spanish physicians prescribed ten men with fully developed type 2 diabetes a moderate form of exercise. Over four months, the patients exercised two days per week, but did not have to change their eating habits (their intake of energy in the food actually rose by 15 percent). The result: The total average weight of the participants remained the same, but the fat distribution had shifted toward a more benign pattern. The fat deposits around the belly that are believed to be particularly bad for one’s health shrank by 10 percent. Furthermore, the blood-sugar levels dramatically improved. These findings show that regular exercise pays off, even when it isn’t accompanied by loss of weight.
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Statisticians at the University of Leicester in England wanted to know whether lifestyle changes could even turn around the symptoms of an emerging diabetic sickness. Recently, they carried out a survey of the medical literature and tracked down a total of 17 trials, covering 8,084 subjects. This meta-analysis revealed that “lifestyle interventions seem to be at least as effective as pharmacological interventions,” with the additional bonus of creating fewer adverse reactions. The survey is good news for people already showing early symptoms of diabetes: moderate exercise can cut the risk of fully contracting this insidious illness by half.
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For healthy people, it’s also worth heeding this advice because the onset of diabetes is inversely correlated to the fitness of a person. This is the central message of a large epidemiological study involving more than 84,000 nurses: If you eat a balanced diet, avoid becoming overweight, are a nonsmoker, drink modest amounts of alcohol, and exercise for 30 minutes a day, you will dramatically increase your chances of never getting diabetes in the first place.
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