Younger adults who get either little sleep or a lot of it may see a greater expansion in their waistlines（腰围）over time, a study published suggests. Researchers found that among black and Hispanic adults younger than 40, those who typically slept for five hours or less each night had a greater accumulation of belly fat over the next five years, versus（相比于） those who averaged six or seven hours. Those who slept eight hours or more in bed each night also showed a bigger fat gain - but it was less obvious than that seen in "short sleepers."
The study, reported in the Journal Sleep, does not prove that too little or too much sleep directly leads to excess fat gain. But the findings support and extend those of other studies linking sleep duration - particularly a lack of sleep - to weight gain and even to higher risks of diabetes(糖尿病) and heart disease. Among participants younger than 40, the study found, those who said they slept for five hours or less each night gained more belly fat than those who averaged six or seven hours of sleep. On average, short sleepers showed a 32 percent gain in visceral（内脏的）fat, versus a 13 percent gain among those who slept six or seven hours per night, and a 22 percent increase among men and women who got at least eight hours of sleep each night. A similar pattern was seen with superficial abdominal（腹部）fat.
The findings, according to lead researcher Dr. Kristen G. Hairston, support the belief that sleep habits affect weight and health in general. "Sleep is an important part of your overall health - not just in whether you're tired during the day," she said.
There may be indirect effects; people who get too little sleep may be too tired during the day to exercise, while those who spend a lot of time in bed may spend less time being active, relative to people who sleep fewer hours. Research also suggests that sleep loss alters people's levels of appetite-regulating hormones（荷尔蒙）- which could, in theory, cause them to overeat. Depression, which often affects people's sleep and has been linked to weight gain, could also be a factor, Hairston noted.
Who may have the higher risk of being fat over the next five years?

A．Jack, a Hispanic man, aged 35, sleeps for 3 hours every night.

B．Candy, a black woman, aged 41, sleeps for about 5 hours every night.

C．Bob, an American, aged 50, sleeps for more than 12 hours every day.

D．John, a student in Africa, sleeps for more than 6 hours every week.

What does the study, reported in the Journal Sleep find?

A．Too little or too much sleep directly gives rise to the fat gain.

B．People are subject to heart disease due to the lack of sleep.

C．It is admitted that sleep plays an important part in our health.

D．Researchers find a longer sleep time is better for our health.

What does the lead researcher Dr. Kristen G. Hairston agree with?

A．People should do some exercise in their daily life.

B．There is a close link between sleep habits and health.

C．More nutrition is greatly needed when we lack sleep.

D．More and more people tend to sleep less than before.

What can we infer from the passage?

A．Younger adults getting little or much sleep may become fat.

B．We are supposed to do exercise as much as possible to keep fit.

C．We should keep a good sleep habit to improve our health.

D．We have to spare no efforts to drive depression away.

What’s the best title of the passage?

A．Sleep Habits Linked to Fat Gain in Younger Adults.

B．Doing Exercise Is the Best Way to Keep Fit.

C．Our Waistlines Can Be Driven Away Right Now.

D．Diabetes No Longer bother all of Young People.