People with more muscle mass and less visceral fat have younger brains

This study looked at whether visceral fat (fat around organs) and subcutaneous fat (fat under the skin) are linked to brain volume. While they found statistically significant differences, the actual effects were very small. The authors acknowledge that the significance was mainly due to the large number of participants rather than meaningful brain differences. Additionally, because this was a snapshot in time, it cannot show whether fat actually causes changes in brain volume. The study also didn't account for other important factors like physical activity, diet, genetics, or menopause status, which should be examined in future research. This study doesn't study muscle mass, neither mentioned brain age.