The prevalence of obesity in children and adolescents worldwide has quadrupled since 1975 and is a key predictor of obesity later in life. Previous work has consistently observed relationships between macroscale measures of reward-related brain regions (e.g., the nucleus accumbens [NAcc]) and unhealthy eating behaviors and outcomes; however, the mechanisms underlying these associations remain unclear. Recent work has highlighted a potential role of neuroinflammation in the NAcc in animal models of diet-induced obesity. Here, we leverage a diffusion MRI technique, restriction spectrum imaging, to probe the microstructure (cellular density) of subcortical brain regions. More specifically, we test the hypothesis that the cell density of reward-related regions is associated with obesity-related metrics and early weight gain. In a large cohort of nine- and ten-year-olds enrolled in the Adolescent Brain Cognitive Development (ABCD) study, we demonstrate that cellular density in the NAcc is related to individual differences in waist circumference at baseline and is predictive of increases in waist circumference after 1 y. These findings suggest a neurobiological mechanism for pediatric obesity consistent with rodent work showing that high saturated fat diets increase gliosis and neuroinflammation in reward-related brain regions, which in turn lead to further unhealthy eating and obesity.

自1975年以来，全世界儿童和青少年中的肥胖症患病率已经翻了两番，并且是以后肥胖症的重要预测指标。以前的工作一直观察到奖励相关的大脑区域（例如伏隔核[NAcc]）的宏观测量与不健康的饮食行为和结果之间的关系。但是，这些关联的基础机制仍不清楚。最近的工作强调了在饮食诱导的肥胖动物模型中神经炎症在NAcc中的潜在作用。在这里，我们利用扩散MRI技术，限制光谱成像来探测皮层下大脑区域的微观结构（细胞密度）。更具体地说，我们测试了与奖赏相关的区域的细胞密度与肥胖相关的指标和早期体重增加相关的假设。在参加青少年脑认知发育（ABCD）研究的一大批9岁和10岁儿童中，我们证明了NAcc中的细胞密度与基线时腰围的个体差异有关，并且可以预测腰围增加1年后的周长。这些发现表明，与啮齿动物工作一致的小儿肥胖症的神经生物学机制表明，高饱和脂肪饮食会增加与奖励相关的大脑区域的神经胶质增生和神经炎症，进而导致进一步的不健康饮食和肥胖症。