Obesity's main causes are well known - an unhealthy diet and lack of exercise. The dangers of being too fat are, however, often underestimated. Together with hypertension and high levels of fat and sugar in the blood, it plays in a deadly quartet that quickly becomes metabolic syndrome (MTS). The metabolism of MTS sufferers increasingly veers off course and could lead to a heart attack or stroke. Millions of people, especially over 40 years are at risk, says Hartmut Becker of the German health foundation, Exclamation Point, near Munich. One cause of MTS is obesity, especially deposits of fat around the internal organs, noted Alfred Wirth of the German Adiposity Society in Hamburg. He said the fat was broken down into free fatty acids that blunt the action of insulin, which the pancreas produces to keep blood sugar levels constant. That, put simply, can lead to diabetes. According to Markus Hanefeld of Dresden, who studies metabolic syndrome, people with MTS are at considerably greater risk of developing diabetes. Since the amount of fat in the blood also increases, deposits build up in the arteries. Both diabetes and obesity raise blood pressure, increasing the chances of a cardiovascular disorder or even heart attack. Measuring one's waistline is one way of assessing the risk, experts point out. Becker, a general practitioner, said the danger zone for men was more than 102 cm and for women, more than 88 cm. The sooner countermeasures are taken, the better the chances of staying healthy, Wirth remarked. When obese persons with MTS lose a lot of weight, he said, the majority also leave their MTS behind. "There are no special diets," said Becker, who suggested "unsaturated instead of saturated fats, for example fish once or twice a week, roughage and a lot of fruit and vegetables." Regular exercise is also important. Drugs are an alternative. Some can improve the action of insulin; others impede the assimilation of fat. But all of them have side effects, Becker warned. The interrelations of obesity, diabetes, high blood pressure and lipometabolism are not fully known. Professor Wolfgang Kerner of the German Diabetes Society in Dusseldorf noted that nobody knew for certain whether insulin resistance was the main cause of MTS. "We want to raise awareness that a time bomb is ticking" for people with MTS, said Becker. Meanwhile, Wirth said his primary aim was to convince people of the danger of obesity. "People think that if they feel good, they are healthy," Wirth said. But there was no such thing as a healthy fat person - "only a fat person who has not fallen ill yet."