Please answer the following question: BEIJING, Jan. 11(Xinhuanet)-- Sleeping a little bit longer a day might help fight against obesity , a recent study shows. The research-- published in the Archives of Internal Medicine along with an editorial by Turek and Northwestern colleague Joseph Bass commenting on it and related research-- after comparing people of normal weight- a body mass index of less than 25- with those who were overweight or _ , found that sleeping for an extra 20 minutes each night could offer a pain-free way to lose weight. Insufficient sleep is linked with changes in hormone levels that may stimulate appetite. A series of studies in recent months have shown that the less people sleep, the heavier they tend to be. American researcher Robert Vorona from Eastern Virginia Medical School in Norfolk and colleagues have now examined the relationship between people's self-reported sleep time per 24 hours and their body mass index(BMI). They found that total sleep time and BMI were inversely correlated was total sleep time decreased, BMI increased, except in the severely obese group." Americans experience insufficient sleep and corpulent bodies. Clinicians are aware of the burden of obesity on patients," the study said. "Our findings suggest that major extensions of sleep time may not be necessary, as an extra 20 minutes of sleep per night seems to be associated with a lower body mass index," it added. "We warn that this study does not establish a cause-and-effect relationship between restricted sleep and obesity (but) investigations demonstrating success in weight loss via extensions of sleep would help greatly to establish such a relationship." In November 2004, researchers from Columbia University in New York City, New York demonstrated a clear link between the risk of being obese and hours of nightly sleep, finding that people aged 32 to 59 who slept four hours or less per night were 73% more likely to be obese than people who slept between seven and nine hours per night. According to the text , the author intends to tell us that _ . A) Sleeping a little bit longer a day might help fight against obesity B) insufficient sleep is linked with changes in hormone lives C) there exists a clear link between the risk of being obeses and hours of nightly sleep D) the less people sleep , the heavier they tend to be
Answer:
A