Background There is considerable policy interest in promoting behaviours with health and environmental co-benefits, but current research has typically focused on single behaviours in isolation rather than on understanding healthy, sustainable lifestyles more broadly. The aim of this study was to describe the prevalence and socio-demographic patterning of healthy, low-carbon (HLC) lifestyles in the UK population by identifying clusters of travel and dietary behaviours that have implications for both human health and carbon emissions.

Methods We analysed self-reported data from participants in UK Biobank (aged 39–72) who completed a 24 hour dietary recall questionnaire (n=211,049). Measures of travel behaviour included transport mode(s) for both commuting and non-work journeys (car, public transport, walking, cycling) as well as average daily driving time. Measures of dietary behaviour included consumption of red and processed meat (RPM), fruit and vegetables, and vegetarian status. We used latent class analysis (LCA) to identify unique clusters of travel and dietary behaviour and characterised each group as ‘higher-carbon’ or ‘lower-carbon’ based on its indicators. Best-fitting LCA models were selected using information criteria and interpretability. Multinomial logistic regression was used to examine socio-demographic differences between each cluster, compared to the highest-carbon class. All analyses were stratified by sex due to gender differences in diet and active travel behaviour.

Results The best-fitting models identified 10 different classes among females and 9 among males. The largest classes were characterised by higher car use (2–4 hours/day) and higher RPM consumption (>1 serving/day) representing 72% of males, and 65% of females. The proportion leading entirely HLC lifestyles (composed of female cyclists, urban vegetarians) was very small (3%). Several groups comprised a much larger segment whose lifestyles were partially or predominantly HLC (20% of males, 27% of females). In fully adjusted multinomial models, the most consistent predictors of HLC lifestyles (across all classes) were having higher qualifications, residing in an urban postcode, and living in and around London.

Discussion This is the first study to measure HLC lifestyles in the UK based on combinations of travel and dietary behaviour. We found that wholly HLC lifestyles are very rare and particularly scarce outside of the most highly urbanised areas, however a sizable minority of the population engages in behaviours that are partially or predominantly HLC. The existence of clustering between travel and dietary behaviours suggests that there is a policy role for establishing stronger links between these areas and for promoting HLC lifestyles more holistically.