It focuses on the importance of eating real, whole food over any sort of junk food or food like product.
Heavy processing of food - which improves shelf life and palatability - also removes nutrients, adds chemicals and makes food more readily absorbable, which might be a problem for insulin and fat metabolism.
That’s why you should try to avoid heavily processed foods, labeled by Michael Pollan as “edible foodlike substances.”
"They’re highly processed concoctions designed by food scientists, consisting mostly of ingredients derived from corn and soy that no normal person keeps in the pantry, and they contain chemical additives with which the human body has not been long acquainted. Today much of the challenge of eating well comes down to choosing real food and avoiding these industrial novelties1."