What do spoons taste of? What can cohort studies tell us about the drivers of obesity? How do drugs and bugs interact with their hosts in metabolism – and what exactly is a host? These were some of the many questions raised (if not completely answered) in the Metabolism & Society@UCL symposium that I attended on 16 February. Culinary (and faecal) metaphors were in abundance – this was described by some as a smorgasbord of an event, highlighting the huge range of research across the disciplines being carried out in UCL in the area of metabolism and society.
The opening keynote was from Steve Simpson who directs the Charles Perkins Centre at the University of Sydney. His talk entitled ‘Putting the Balance Back in Diet: The Nutritional Geometry of Metabolic Disease’ began with an account of the modelling of a multi-dimensional ‘nutritional space’ and moved on to analyse the results of a number of extraordinary animal studies (mostly of primates) which demonstrated how consistently across different environments, they ‘targeted’ a 15% protein to non-protein ratio in their diet. Simpson went on to argue that evidence from a range of hunter-gatherer societies (with very different kinds of diets) showed that humans in food sufficient contexts also ‘leverage’ protein at about 10-25% of total energy intake and that this is achieved across cycles of gain and loss or body fat. He went on to talk about modern ultra-processed foods as “protein decoys” and about the possible costs to eating too much protein. Longer-lived healthy animals are apparently fat – and adiposity is healthier on a low protein high carbohydrate diet. Since most of us now live in food environments dominated by processed foods, the question is how we can manage the protein leverage effect. Simpson was keen to stress complexity – and the interactive nature of metabolic processes.
Over the course of the day a whole range of papers from widely different perspectives examined the complexity of metabolic processes – how they are shaped by society and history and how they in turn shape us. Most speakers had 10 minutes, which was not really enough for Jonathan Wells to summarise his holistic and politically engaged account of the creation of the ‘Metabolic Ghetto’. Informed by history, anthropology and social theory, as well as by evolutionary biology and theories of the developmental origins of disease, Wells’ book demonstrates the degree to which social and economic inequality have contributed to the rise of metabolic disorders. His work is a reminder that not everyone can choose what they eat – and since so much health education assumes that they do, this is a critical issue.
But what is metabolism anyway? Hannah Landecker from UCLA gave the final keynote in which she outlined the history of the concept of metabolism from its origins in the mid nineteenth century to the present. She showed how ‘food as fuel’ (a kind of combustion engine) in the industrialising nineteenth century has been transformed into ‘nutrition as information’ in the science of the ‘post-industrial’ era. Epigenetics and the microbiome now enter the picture, complicating both the temporalities of metabolic thinking and the assumption that the ‘body’ is distinct from the ‘environment’ that it eats and breathes.