Over the last 20 years there has been an increasing interest in the influence of the gastrointestinal tract on appetite regulation.
Much of the focus has been on the neuronal and hormonal relationship between the gastrointestinal tract and the brain. There is
now mounting evidence that the colonic microbiota and their metabolic activity have a significant role in energy homeostasis. The
supply of substrate to the colonic microbiota has a major impact on the microbial population and the metabolites they produce,
particularly short chain fatty acids (SCFAs). SCFAs are produced when non-digestible carbohydrates, namely dietary fibres and
resistant starch, undergo fermentation by the colonic microbiota. Both the consumption of fermentable carbohydrates and the
administration of SCFAs have been reported to result in a wide range of health benefits including improvements in body
composition, glucose homeostasis, blood lipid profiles and reduced body weight and colon cancer risk. However, published studies
tend to report the effects that fermentable carbohydrates and SCFAs have on specific tissues and metabolic processes, and fail to
explain how these local effects translate into systemic effects and the mitigation of disease risk. Moreover, studies tend to
investigate SCFAs collectively and neglect to report the effects associated with individual SCFAs. Here, we bring together the recent
evidence and suggest an overarching model for the effects of SCFAs on one of their beneficial aspects: appetite regulation and
energy homeostasis.