## 3 Results and Discussion
The controversy and debate surrounding the claim that a higher BMI in late life is associated with a decreased likelihood of developing dementia among older adults is acknowledged. However, there is a paucity of studies that directly address this issue. A study involving nearly two million individuals in the UK found that the risk of dementia decreases as the body mass index (BMI) increases in older age. The findings indicated that individuals with a BMI above 40 kg/m\({}^{2}\) exhibited a 29% lower risk of dementia compared to those with a normal BMI. Furthermore, the risk of dementia was observed to be highest in underweight individuals (BMI \(<\) 20 kg/m\({}^{2}\)), who demonstrated a 34% higher risk compared to individuals with a normal BMI. The underlying mechanisms that precipitate these observations may be associated with the energy reserve provided by a higher BMI, particularly among older adults, who are susceptible to losing muscle mass and body fat [36]. Additionally, the impact of a higher BMI on reducing the risk of malnutrition and sarcopenia, which are strongly associated with cognitive decline, could be a contributing factor. Furthermore, the BMI in older age may serve as a marker of overall metabolic health, which could offer a protective effect on the brain. This assertion is further substantiated by the findings of [PERSON] et al. [36], who conducted a retrospective cohort study encompassing two million individuals over a two-decade period. Their research, published in the Lancet Diabetes Endocrinol, revealed that the BMI is associated with a reduced risk of dementia. As indicated by the authors of article [37], a correlation between the BMI and the risk of developing dementia has been identified, particularly in the context of weight fluctuations across various stages of life. The epidemiological studies presented demonstrate that a high BMI in middle age is associated with an increased risk of dementia, while an elevated BMI in later life is linked to a reduced risk of dementia. Conversely, weight loss or a low BMI in later life is associated with an elevated risk of developing dementia. This observation suggests a potentially protective role for a higher BMI in late life. Considering the study by [PERSON] et al. [38], it is noteworthy that their findings indicate that low levels of muscle mass, independent of muscle strength, are associated with an accelerated decline in executive function in elderly individuals. This association remained significant even after controlling for variables such as the body fat percentage, hand grip strength, and level of physical activity. These findings offer a potential explanation for the seemingly \"contradictory\" observations reported in the literature regarding the relationship between the BMI and cognitive function. A low index of muscle mass (ALM) has been associated with a decline in executive function, which encompasses abilities such as problem-solving, organization, and working memory, functions that are crucial to maintaining independence in daily activities among older adults. In the context of this study, weight loss, including the loss of muscle mass, can be a risk marker for accelerated cognitive decline. The authors identified potential mechanisms to explain the association of a high BMI with cognitive function:  
* Higher body fat levels may provide an energy reserve, which is particularly important for older people at a higher risk of malnutrition and sarcopenia;
* Skeletal muscles secrete myokines (e.g., BDNF), which may benefit cognitive function by promoting brain health;
* A higher BMI may help reduce oxidative stress and chronic inflammation, both of which are associated with sarcopenia and dementia.