As I have always said, nutrition and metabolism is not always that simple. For some context of why, please visit this website for a (simplified) overview of what we know about metabolism so far: http://biochemical-pathways.com/#/map/1 (by the way, you can order this as a wall poster. Probably something @john.tavis would love 
). Just one change in one step and the balance of what comes out can be altered. These processes are acting in each of our cells, which also interact with each other, complicating things even more.
This diagram doesn’t even take into account differences in enzyme activity for each of these steps that are affected by a person’s DNA make-up (both cellular AND mitochondria), the gut bacteria (which can alter what is absorbed by the body based on THEIR metabolism), the gut viruses (most of which infect bacteria and so alter how THEY metabolise), someone’s mental state (which can alter stress hormones, hunger signals, etc). All of these are interacting and contribute to someone’s end state. Exactly which factor is actually causing the state at the end, you’ll probably never know without some trial and error with lifestyle changes.
There are general things you can say (e.g. the Western diet probably has too much salt and sugar to be healthy), but anything more specific is really hard. This is basically the reason I’ve stayed out of research in metabolism, it’s just too hard!
To address a query from @Kinoti, I believe there is research showing that peripheral fat (seen in the arms, legs, belly, etc.) is actually quite different to visceral fat (which surrounds and is within our organs). They are regulated differently, use different cells, and importantly have different health outcomes. Visceral fat is probably worse for our health than peripheral fat.
Thomas