一项新的研究发现，与体重正常人群相比，肥胖人群脑组织含量少8%左右，他们的大脑也要比后者衰老约16年。而超重人群与正常人相比，脑组织含量缺少约4%，脑龄衰老8年。据研究人员称，脑组织的缺失会使人逐渐丧失认知，从而极大的增加了患有老年痴呆症，或其他脑损伤疾病的风险，但是人们仍然可以通过合理饮食和控制体重，来降低发病的可能。

An undated image of the human brain taken through scanning technology.

A new study finds obese¹ people have 8 percent less brain tissue than normal-weight individuals. Their brains look 16 years older than the brains of lean individuals, researchers said today.

Those classified as overweight have 4 percent less brain tissue and their brains appear to have aged² prematurely³ by 8 years.

The results, based on brain scans of 94 people in their 70s, represent "severe brain degeneration," said Paul Thompson, senior author of the study and a UCLA professor of neurology.

"That's a big loss of tissue and it depletes⁴ your cognitive⁵ reserves, putting you at much greater risk of Alzheimer's and other diseases that attack the brain," said Thompson. "But you can greatly reduce your risk for Alzheimer's, if you can eat healthily and keep your weight under control."

The findings are detailed⁶ in the online edition of the journal Human Brain Mapping.

Obesity⁷ packs many negative health effects, including increased risk of heart disease, Type 2 diabetes⁸, hypertension and some cancers. It's also been shown to reduce sexual activity.

More than 300 million worldwide are now classified as obese, according to the World Health Organization. Another billion are overweight. The main cause, experts say: bad diet, including an increased reliance on highly processed foods.

Obese people had lost brain tissue in the frontal and temporal lobes¹⁰, areas of the brain critical for planning and memory, and in the anterior¹¹ cingulate gyrus (attention and executive functions), hippocampus (long-term memory) and basal ganglia (movement), the researchers said in a statement today. Overweight people showed brain loss in the basal ganglia, the corona¹² radiata, white matter comprised of axons, and the parietal lobe⁹ (sensory lobe).

"The brains of obese people looked 16 years older than the brains of those who were lean, and in overweight people looked 8 years older," Thompson said.

Obesity is measured by body mass index (BMI), defined as the weight in kilograms divided by the square of the height in meters. A BMI over 25 is defined as overweight, and a BMI of over 30 as obese.

Vocabulary:

deplete：耗尽，衰竭

Alzheimer：阿兹海默氏症， 老人痴呆症