The prevalence of obesity among adults more than doubled worldwide between 1990 and 2022, affecting around 890 million people. Obesity is a chronic disease characterized by excessive body fat, which increases the risk of numerous comorbidities, such as type 2 diabetes, cardiovascular diseases and certain cancers. Emerging evidence suggests that obesity may also contribute to chronic low-grade neuro-inflammation, systemic inflammation and microbiome dysbiosis, potentially leading to neuropsychiatric disorders and cognitive impairment. This systematic review aims to determine if obesity is an independent risk factor for cognitive impairment. Our review will focus on prospective cohort studies in order to establish a causal relationship, taking into account the limitations of previous reviews that relied mainly on cross-sectional studies. We will include studies of adult participants (aged between 20-50 years) suffering from obesity, using the body mass index as a measure of obesity, and who were compared with normal-weight control groups. Impaired cognitive function must have been established by means of valid cognitive tasks or psychological tests. By updating and summarizing the latest evidence, this review attempts to clarify the independent effect of obesity on cognitive functioning. This understanding is crucial for the development of targeted prevention and intervention strategies to mitigate the adverse effects of obesity, ultimately contributing to improved public health outcomes. This protocol was submitted to the "International prospective register of systematic reviews" PROSPERO on July 26, 2024.