It might be that this is still undergoing research. Originally published in 2002 [1] a later followup paper in 2019 [2] points out ADHD points to a number of inflammation-related conditions like asthma and obesity. It's still not known the exact underlying mechanisms! I'm just really interested that obesity seems to be increasingly not a voluntary choice.

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC130024/

2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6826981/