If you're middle-aged¹ and your memory's not what it used to be, check the bathroom scale, researchers warned, suggesting overweight people tend to score more poorly on tests of memory than their thinner peers do.

The findings suggest that a heavier weight in middle age may mean a higher risk of dementia later in life.

Reporting in the journal Neurology, the researchers speculated that higher rates of cardiovascular disease or diabetes² might help explain the link. But it's also possible that substances produced by fat cells, such as the hormone³ leptin, have direct effects on the brain.

The study compared mental abilities to body mass index (BMI), a measurement of weight in relation to height used to define overweight and obesity⁴. A BMI of 25 or more indicates overweight, and 30 or more is obese⁵.

The study also investigated the relationships between BMI and cognitive⁶ function in 2,223 healthy men and women between the ages of 32 and 62 in France through the use of four cognitive tests.

The study found a higher BMI was associated with lower cognitive test scores. Results from a test involving word memory recall show people with a BMI of 20 remembered an average of nine out of 16 words, while people with a BMI of 30 remembered an average of seven out of 16 words.

研究人员提醒，如果你已步入中年，发现自己的记忆力不如从前，那么你得小心体重了。研究表明，超重的人记忆测试的得分要比较瘦的人低。

研究发现，体重偏大的中年人今后患老年痴呆症的可能性较大。

研究报告在《神经学》期刊上发表，研究人员推断，心血管疾病及糖尿病的高发现象可以解释其中的原因。此外，脂肪细胞所产生的物质，如瘦体激素，对大脑有直接影响。

此项研究将调查对象的智力与体重指数进行了对比。体重指数指的是身高和体重之间的比例，主要用来衡量一个人是否偏胖或肥胖。体重指数为25或25以上的人偏胖，达到30或30以上的人则为肥胖。

研究人员还对体重指数和认知功能间的关系进行了研究，他们在法国对2223位年龄在32岁至62岁间的健康男女进行了认知测试。

研究发现，体重指数越大，认知测试的得分越低。其中一项"单词记忆"的测试结果表明，在16个单词中，体重指数为20的人平均能记住9个，而体重指数为30的人平均只能记住7个。