I am an obese mother and my son is obese. definately hereditory and cross gender too!
since my other son living in the same house is lean [and active]. What my son that is obese and I share is what is called physical laziness or you could also call it reluctence to engage in sportivic activities, due to muscle pain in every atempt of physical activity.
The underlying cause is not clear. I remember myself even as an adolescent strugling to maintain weight and can report muscular difficulties even as a normal weight person. So, I would summarize that this research is in complete.