There is NO body of direct evidence that shows that the American propensity towards obesity is CAUSED by, or even greatly influenced by, refined foods.
How do I gently say "Bullshit"? You don't need a 'direct body of evidence' (whatever that is) to understand a few simple facts:
1) Overprocessed foods (most of what we eat) have been stripped of their original nutrients, vitamin, minerals, enzymes, etc. IOW, the stuff your body needs. Fructose, fat, chemicals, preservatives, colorings, artificial 'flavorings', and all sorts of (who knows what?) are added.
2) The human body needs the nutrients, not the additives.
3) People eat more (yes, that's the cause of obesity, eating more as a result of processed foods), they ingest more sugars and fats while their bodies are screaming for basic nutrients, and the wind up being huge waddling fatasses.
If you need a protracted multimillion dollar 'study' to demonstrate that, I think you're way behind the power curve, so to speak.