That’s a proposal in a recent scientific article, from which I quote:
The present hypothesis suggests that in parallel with the bacterial effects of sugars on dental and periodontal health, acellular flours, sugars, and processed foods produce an inflammatory microbiota via the upper gastrointestinal tract, with fat able to effect a “double hit” by increasing systemic absorption of lipopolysaccharide. This model is consistent with a broad spectrum of reported dietary phenomena. A diet of grain-free whole foods with carbohydrate from cellular tubers, leaves, and fruits may produce a gastrointestinal microbiota consistent with our evolutionary condition, potentially explaining the exceptional macronutrient-independent metabolic health of non-Westernized populations, and the apparent efficacy of the modern “Paleolithic” diet on satiety and metabolism.
You can read the whole shebang free online.
Reference: Spreadbury, Ian. Comparison with ancestral diets suggests dense acellular carbohydrates promote an inflammatory microbiota, and may be the primary dietary cause of leptin resistance and obesity.Diabetes Metab Syndr Obes. 2012; 5: 175–189. Published online 2012 July 6. doi: 10.2147/DMSO.S33473 PMCID: PMC3402009