Poor diet and obesity are associated with cognitive impairment throughout adulthood, and increased dementia risk in aging. Here we review the current literature interrogating the mechanisms by which diets high in fat, or fat and sugar lead to cognitive impairment, focusing on changes to gut microbiome composition, inflammatory signalling and blood-brain barrier integrity. Preclinical studies indicate weight gain is not necessary for diet-induced cognitive impairment. Rather, gut microbiome composition, and systemic and central inflammatory processes appear to contribute to diet-induced cognitive impairment. While both obese humans and rodents exhibit reduced blood-brain barrier integrity, cognitive impairments precede these changes, suggesting other mechanisms may underly diet-induced cognitive changes. Other potential candidates include hormone, glucoregulatory and cardiovascular changes. Poor diet and obesity act through multiple mechanisms to affect cognitive health and the challenge for future research is to identify key processes that can be reversed to improve cognition and quality of life.

饮食不佳和肥胖与整个成年期的认知障碍有关，并增加了老年痴呆的风险。在这里，我们回顾了目前的文献，这些文献审视了高脂肪，高脂肪和高糖饮食导致认知障碍的机制，重点是肠道微生物组组成的变化，炎性信号传导和血脑屏障完整性。临床前研究表明，体重增加对于饮食引起的认知障碍不是必需的。相反，肠道微生物组组成以及全身性和中枢性炎症过程似乎会导致饮食引起的认知障碍。虽然肥胖的人和啮齿动物都表现出血脑屏障完整性的降低，但认知障碍先于这些变化，表明其他机制可能是饮食引起的认知变化的潜在原因。其他可能的候选药物包括激素，糖调节和心血管变化。不良的饮食和肥胖通过多种机制影响认知健康，未来的研究面临的挑战是确定可以逆转的关键过程，以改善认知和生活质量。