Modelling individual responses to healthier diets: new ways to quantify the importance of physiology and behaviour for successful dietary changes

Diet is a major determinant of health. Traditionally, effects of diet on health parameters are determined as the average response in a population. However, it is estimated that only 40% of any population responds to a dietary intervention. Precision nutrition approaches investigate effects on the individual level by single subject studies. In these so-called 'n-of-1 trials', multiple data are collected over time as the individual undergoes different treatments. This enables us to study how genetic, phenotypic and environmental factors shape an individual's response, and to what extent this differs from the average population responses, to dietary interventions. If enough data are collected over a sufficiently long time, and by looking for commonalities across multiple n-of-1 studies, the data can be aggregated to predict effectiveness of dietary interventions in defined population groups. The Food4Me study showed that personalised diets, based on predicted individual responsiveness, can be an effective strategy to improve individual health. The objective of this project is to quantify differences in health responses to specific dietary changes between individuals, and to identify which personal physiologic characteristics and factors determine this variation. We will also investigate the importance of psychological and behavioural factors, in relation to physiological determinants, for individual responsive.

This project will consist of three interlinked phases that exploit new mathematical methodologies and combine physiological and behavioural sciences. to better understand what drives individual effects and success of dietary changes. In the first phase we will make use of available high-quality datasets with repeated measurements of relevant outcomes from randomised controlled intervention studies to re-analyse data with n-of-1 statistics, followed by aggregation of multiple n-of-1 trials to investigate how physiological and behavioural factors contribute to responses in metabolic markers. We postulate that this approach will enable accurate prediction of individual responses to dietary interventions. In the second phase of the project we will conduct a proof-of-principal 'n-of-1' dietary intervention study in which a large number of responses to a diet will be measured in a limited number of subjects. This will reveal whether an observed change in a health outcome of interest is indeed caused by the dietary treatment or just due to normal biological fluctuations. In collaboration with the consumer science group at Unilever R&D, the PhD student will explore the role of psychological and behavioural factors that determine individual responses to short- or long-term consumption of healthier foods. To achieve this, both behavioural aspects (knowledge, perception, self-efficacy, social norms and intentions and reward will be measured in the proof-of-principle study.