A study published in the journal Neurology found that exercise can help protect brain cells. It explained that exercise helps in maintaining insulin and body mass index levels which in turn protects brain volume and help reduce the risk of dementia. The study author added that the results help us to understand the link between physical activity and brain health that may usher us toward developing new interventions to prevent or delay age-related memory loss.

The author also added that maintaining a lower BMI helps in regulating insulin metabolism in older age and thus promoting brain health. 

However, in contrast, researchers have found that the link between exercise and the metabolism of glucose is not affected by insulin and BMI and reduced glucose metabolism can be seen in people with dementia. The study involved 134 people with an average mean age of 69 years with no memory problems. Based on the survey questionnaire, brain scan, BMI value, cholesterol, blood pressure, and other factors it was determined that people with the most physical activity had a higher total volume of grey matter in their brain. When researchers evaluated the results with regards to Alzheimer’s disease, they found insignificant values as no association between physical activity and amyloid plaque formation in the brain could be established. 

(Source: https://www.hindustantimes.com/lifestyle/health/exercise-may-protect-brain-volume-by-keeping-insulin-bmi-levels-low-study-101650084118811.html )