试题详情
阅读理解
Night owls may be prone to heart disease and diabetes (糖尿病) than early birds because their bodies are less able to burn fat for energy, U. S. researchers say. People who rise early rely more on fat as an energy source. They are often more active in the day than those who stay up later, meaning fat may build up more easily in night owls, the scientists found.
The findings may help explain why night owls are at greater risk of type 2 diabetes and cardiovascular disease. They may also help doctors to identify patients early on who are more likely to develop the conditions.
The researchers divided 51 fat middle-aged adults into early birds and night owls, depending on their answers to a questionnaire on sleeping and activity habits. They monitored the volunteers' activity pattern for a week and tested their bodies' fuel preference at rest and while performing moderate or high-intensity exercise on a treadmill.
In Experimental Physiology, the team described how early birds were more sensitive to blood levels of the hormone insulin (胰岛素) and burned more fat than night owls while at rest and during exercise. The night owls were less sensitive to insulin and their bodies favored carbohydrates over fat as an energy source.
Prof Steven Malin, a senior author on the study and an expert in metabolism, said it was unclear why differences in metabolism were seen in night owls and early birds. But one possibility, he believes, is a mismatch between the time people go to bed and wake the next morning and the circadian rhythms (昼夜节奏) that govern their body clocks.
The findings could affect discussions around the health risks of night-shift work and even changing the clocks to suit daylight hours. "If we promote a timing pattern that is out of sync with nature, it could worsen health risks, " Malin said. "Whether dietary patterns or activity can help reduce these is an area we hope becomes clear in time. "
试题所涉知识点
