I think, as you surmise, generalized metabolic inflammation is almost inescapable if one lives anywhere but 3d-world subsistence countries...the current diets in the US and Europe are chock-full of natural and synthetic molecules that our bodies were simply never evolutionarily developed to consume and therefore register as "alien" and cause inflammation...everywhere. Chronic inflammation is understood at this point to be absolutely anathema to the healthy functioning of the human body, and the greater the inflammation and the longer it is present works adversely on all genetic variations of people. So, although "diet and exercise" is vastly important in consideration of gradients of health (in the developed countries, at least) isn't going to have the effect you presume on weight and health in general. We have woven our environment with too many toxins and molecules that we ingest that our amazing bodies were never made to process. And those toxins and "foreign" molecules are, unfortunately, inescapable in modern life.