From reading the proof, it seems the authors are mainly focused on “linking” or showing correlation, not causation. Part of me wonders about the directionality

From reading the proof, it seems the authors are mainly focused on “linking” or showing correlation, not causation. Part of me wonders about the directionality of causation here (If we assumed one existed). One could argue the hippocampus, which from my recollection is involved in inhibiting impulsive behavior, has a clear path to being a causative agent for obesity. Distinguishing between the two narratives of “Being overweight inhibits brain function” versus “Differences in part of brain controlling impulses leads to weight differences” is important to resolving it, as it is easier to imagine treatment regimens to combat weight more than brain blood flow. It is also completely possible these two variables do not affect each other, but are correlated. That’s useful still, because it means we may be able to use body weight increases as an inferred marker for the brain changes. It would be incredibly interesting if the story of Alzheimer’s transformed more into “Same factor may be causing both America’s obesity increases as well as Alzheimer’s cases” Edit: Updated this a few times while reading the original paper