tailieunhanh - Ielts practice test plus part 7

IELTS stands for International English Language Testing System It is a test of English language skills designed for students who want to study in the medium of English either at university, college or secondary school. | E In Australia the University of Sydney s Professor Ian Caterson says while major genetic defects may be rare many people probably have minor genetic variations that combine to dictate weight and are responsible for things such as how much we eat the amount of exercise we do and the amount of energy we need. When you add up all these little variations the result is that some people are genetically predisposed to putting on weight. He says while the fast slow metabolism debate may have been settled that doesn t mean some other subtle change in the metabolism gene won t be found in overweight people. He is confident that science will eventually be able to cure some forms of obesity but the only effective way for the vast majority of overweight and obese people to lose weight is a change of diet and an increase in exercise. F Despite the 500 million a year Australians spend trying to lose weight and the 830 million it costs the community in health care obesity is at epidemic proportions here as it is in all Western nations. Until recently research and treatment for obesity had concentrated on behaviour modification drugs to decrease appetite and surgery. How the drugs worked was often not understood and many caused severe side effects and even death in some patients. Surgery for obesity has also claimed many lives. G It has long been known that a part of the brain called the hypothalamus is responsible for regulating hunger among other things. But it wasn t until 1994 that Professor Jeffery Friedman from Rockerfeller University in the US sent science in a new direction by studying an obese mouse. Prof. Friedman found that unlike its thin brothers the fat mouse did not produce a hitherto unknown hormone called leptin. Manufactured by the fat cells leptin acts as a messenger sending signals to the hypothalamus to turn off the appetite. Previously the fat cells were thought to be responsible simply for storing fat. Prof. Friedman gave the fat mouse leptin and it lost 30