A recent study (Chassaing, et al.) showed that two dietary emulsifiers — carboxymethylcellulose and polysorbate-80 — induced gut microbiota alteration and gut barrier dysfunction in mice, resulting in weight gain, low-grade inflammation, and metabolic disorders. While it is unlikely that emulsifiers in processed foods are uniquely responsible for the human pandemic of obesity and inflammatory diseases, we cannot rule out the idea that ingesting combinations of similar compounds could contribute to low-grade inflammation and worse metabolic health in those who may be predisposed to metabolic disease.
Cani PD. (2015) Dietary emulsifiers — sweepers of the gut lining? Nature Reviews Endocrinology 11(6), pp. 319-320. doi:10.1038/nrendo.2015.59
Chassaing B, et al. (2015) Dietary emulsifiers impact the mouse gut microbiota promoting colitis and metabolic syndrome. Nature 519 (7541), pp. 92-96. doi:10.1038/nature14232
See this article for a discussion of potential mechanisms:
Cani PD & Everard A. (2015) Keeping gut lining at bay: Impact of emulsifiers. Trends in Endocrinology and Metabolism 26(6), pp. 273–274 doi:10.1016/j.tem.2015.03.009