美国研究者经由脑部扫描发现,面对诱人的高热量食物,瘦人的大脑可以比胖人调动出更活跃的冲动控制力。这可能是胖瘦分化明显的原因之一。
这项由美国耶鲁大学和南加州大学研究者合作的研究,以报告形式刊登在最新一期《临床研究期刊》月刊。
法新社援引报告内容报道,借助核磁共振成像技术,研究者比对观察胖人和瘦人在面对高热量食物时的大脑反应。结果发现,面对高热量食物的图片时,瘦人大脑中控制冲动区域的活跃度增强,而胖人这一区域活跃程度不明显。
在耶鲁大学康涅狄格医学院研究者罗伯特·舍温看来,这一比对研究说明,“人们之所以不能完全控制对食物的欲望,本质上出于生理因素”。
共有9名偏瘦和5名肥胖志愿者参与比对测试。志愿者在进食两小时后进行脑部扫描,主要观测大脑中负责发出抑制进食信号的大脑前额叶皮质区活跃度。
比对结果显示,饭后两小时,面对高热量食物诱惑,胖人的前额叶皮质区活跃度不及瘦人,换句话说,胖人大脑的抑制进食能力更差。
试验同时测定志愿者血糖值,发现血糖值差异对前额叶皮质区活跃度确实产生影响,但不改变胖人比瘦人抑制进食能力更差的总体状况。
舍温在接受路透社电话采访时说,尽管这一发现有待更大规模研究核实,但胖瘦群体大脑中抑制进食区域活跃度差异确实有可能是胖人更爱高热量食物的原因之一。
这项研究旨在发现导致肥胖的生理因素。在美国,三分之一成年人和将近17%未成年人受肥胖困扰。(生物谷 Bioon.com)
doi:10.1172/JCI57873
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Circulating glucose levels modulate neural control of desire for high-calorie foods in humans
Kathleen A. Page, Dongju Seo, Renata Belfort-DeAguiar, Cheryl Lacadie, James Dzuira, Sarita Naik, Suma Amarnath, R. Todd Constable, Robert S. Sherwin and Rajita Sinha
Obesity is a worldwide epidemic resulting in part from the ubiquity of high-calorie foods and food images. Whether obese and nonobese individuals regulate their desire to consume high-calorie foods differently is not clear. We set out to investigate the hypothesis that circulating levels of glucose, the primary fuel source for the brain, influence brain regions that regulate the motivation to consume high-calorie foods. Using functional MRI (fMRI) combined with a stepped hyperinsulinemic euglycemic-hypoglycemic clamp and behavioral measures of interest in food, we have shown here that mild hypoglycemia preferentially activates limbic-striatal brain regions in response to food cues to produce a greater desire for high-calorie foods. In contrast, euglycemia preferentially activated the medial prefrontal cortex and resulted in less interest in food stimuli. Indeed, higher circulating glucose levels predicted greater medial prefrontal cortex activation, and this response was absent in obese subjects. These findings demonstrate that circulating glucose modulates neural stimulatory and inhibitory control over food motivation and suggest that this glucose-linked restraining influence is lost in obesity. Strategies that temper postprandial reductions in glucose levels might reduce the risk of overeating, particularly in environments inundated with visual cues of high-calorie foods.