英文阅读：啤酒肚更易患痴呆症？
Scientists already know that overweight adults risk developing diabetes,heart problems and other medical conditions. But over the last few years
researchers have noticed that obesity in middle age is linked with cognitive
problems in the aged. Now it seems that overall body mass is not so important –
it's the fat around the belly that appears to cause the problems.
Epidemiologist Rachel Whitmer and colleagues looked at the medical records
of 6583 adults registered with the healthcare firm she works for – Kaiser
Permanente of Oakland, California. During the 1960s and 1970s, records were
taken of the diameters of the adults' bellies, which gave Whitmer a rough idea
of how much fat they were carrying around the waist.
When she compared the measurements with the subjects' current medical
records, the results were startling. Incidence of dementia(痴呆) increased
steadily with the amount of belly fat, such that the 20% with the most belly fat
were over two and half times more likely to develop dementia that those carrying
the least. Levels of total fat also seemed to increase dementia risk, but not by
the same magnitude.
"This is an important paper," says Sudha Seshadri, a neurologist at Boston
University who has also found evidence linking belly fat to cognitive problems.
"I believe the effect is real." The link may seem odd, but Whitmer notes that
the fat around the belly is the most metabolically(新陈代谢地) active of all fat
types.
For example, it secretes larger amounts of cytokines, molecules that carry
chemical signals between cells. Some of these molecules, such as leptin, have
been shown in animal studies to cross the blood-brain barrier, suggesting a
mechanism by which extra weight around the belly could be affecting the
brain.
Yet Seshadri also notes that factors other than fat could be responsible
for the results. Whitmer's team controlled for some of these, such as education
and rates of other illnesses. But other issues were not taken into account.
Overweight people are less likely to exercise, for instance. Physical activity
is known to decrease obesity risk, as well as being psychologically
beneficial.
Researchers next need to study the impact that the molecules released by
body fat have on the brain. If Whitmer's hypothesis proves right, the
conclusions could be disturbing – those beer bellies may be silently damaging
the brain, long before old age sets in. But she notes that there are also
grounds for optimism, since moderate exercise and diet can reduce weight around
the belly more easily that it can in other parts of the body." It's the least
stubborn fat," Whitmer says.
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