Dieting, according to an old joke, may not actually make you live longer, but it sure feels that way. Nevertheless, evidence has been accumulating since the 1930s that calorie restriction—reducing an animal"s energy intake below its energy expenditure—extends lifespan and delays the onset of age-related diseases in rats, dogs, fish and monkeys. Such results have inspired thousands of people toput up with constant hunger in the hope of living longer, healthier lives. They have also led to a search for drugs that mimic the effects of calorie restriction without the pain of going on an actual diet. Amid the hype (intensive publicity), it is easy to forget that no one has until now shown that calorie restriction works in humans. That omission, however, changed this month, with the publication of the initial results of the first systematic investigation into the matter. This study, known as CALERIE (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy), was sponsored by America"s National Institutes of Health. It took 48 men and women aged between 25 and 50 and assigned them randomly to either a control group or a calorie-restriction regime. Those in the second group were requir ed to cut their calorie intake for six months to 75% of that needed to maintain their weight. The CALERIE study is a landmark in the history of the field, because its subjects were either of normal weight or only slightly overweight. Previous projects have used individuals who were clinically obese, thus confusing the unquestionable benefits to health of reducing obesity with the possible advantages of calorie restriction to the otherwise healthy. At a molecular level, CALERIE suggests these advantages are real. For example, those on restricted diets had lower insulin resistance and lower levels of low-density lipoprotein cholesterol. They showed drops in body temperature and blood-insulin levels—both phenomena that have been seen in long-lived, calorie-restricted animals. They also suffered less oxidative damage to their DNA. Eric Ravussin, of Louisiana State University in Baton Rouge, who is one of the study"s authors, says that such results provide support for the theory that calorie restriction produces a metabolic adaptation over and above that which would be expected from weight loss alone. Nevertheless, such metabolic adaptation could be the reason why calorie restriction is associated with longer lifespans in other animals—and that is certainly the hope of those who, for the past 15 years, have been searching for ways of triggering that metabolic adaptation by means other than semi-starvation.
单选题
The evidence since the 1930s has inspired people to _____.