• Coeliac disease
• inflammatory bowel disease
• mucosal immunology

The global epidemic of obesity and obesity-associated disorders, including diabetes, metabolic syndrome and cardiovascular disease, continues apace despite widespread public health education. The problem is also set to emerge in regions undergoing socioeconomic development. The fact that obesity arises from a chronic surplus of energy consumption over energy expenditure is self-evident, but this is not the whole story. Effective preventive strategies need to look beyond simple calorific mathematics.

Among the more intriguing developments in medicine in recent years, the evidence linking indigenous microbiota with obesity and obesity-associated complications has been significant. This is a complex relationship. For example, a direct, obligate role for the microbiota in atherosclerosis has recently been identified with the discovery of a microbial-dependent pathway for metabolism of dietary phospholipids, which generates metabolites that are pro-atherosclerotic after absorption and hepatic metabolism.1 Even more intriguing is the microbial contribution to the metabolic processes underpinning obesity. This involves multi-directional signalling among the microbiota, host metabolism and immunity, with dietary intake influencing each component of this triangular network.2–4

Obesity is characterised by insulin resistance and a state of low-grade inflammation or metabo-inflammation.5 This differs in many respects from classical inflammation: it is induced by nutrient overload, is associated with reduced metabolic rate, is characterised by …