Genotype-based diet and physical activity advice: effects on behaviour change to reduce risk factors for cardiometabolic disease.

The most important aspect of dietary or physical activity advice is that it results in a beneficial change in behaviour. Despite clear evidence that adherence to dietary and physical activity advice can reduce the risk of cardiometabolic disease, a significant proportion of the population do not meet recommendations. Personalised advice based on genetic variation has been proposed to motivate behaviour change, although research to date has been contradictory. The aim of this research was to determine the efficacy of genotype-based personalised advice to motivate and promote dietary and physical activity behaviour change, in the context of reducing the risk of obesity, type II diabetes (T2D), and cardiovascular disease (CVD). Four studies were conducted. The first two were intervention studies investigating: 1) dietary behaviour change following genotype-based personalised nutrition advice in participants (n = 114) informed of a risk versus a non-risk genotype (Study 1); and 2) healthy-eating motivation in young adults (n = 153) after receiving genotype-based personalised advice versus non-genotype-based personalised advice or no advice (Study 2). A systematic review and meta-analysis of 14 reports from 11 randomised controlled trials (RCTs) investigated the efficacy of genotype-based dietary or physical activity advice on behaviour change in the general population and individuals that are at-risk of CVD or T2D (Study 3). Finally, a survey (n = 396) was conducted to investigate the factors that influence the intention to adopt genotype-based personalised advice for diet and physical activity in young adults that perceive themselves to be a healthy weight versus those that perceive themselves to be overweight or obese (Study 4). Genotype-based personalised nutrition advice led to favourable dietary changes in participants who were not meeting dietary recommendations, but only those informed of a risk genotype met saturated fat recommendations following personalised nutrition advice (Study 1). Genotype-based personalised advice did not affect healthy-eating motivation in young adults (Study 2). The meta-analysis suggested that the use of genotype-based advice to promote dietary or physical activity behaviour is no more effective than general advice or advice based on lifestyle or phenotypic measures (Study 3). Background factors including belief composites, health locus of control (HLC), gender, physical activity, and food choice motives of ‘health’, ‘price’, ‘familiarity’, ‘weight control’, and ‘convenience’ interact with Theory of Planned Behaviour (TPB) constructs related to the intention to adopt genotype-based advice in young adults (Study 4). The findings from this programme of research suggest genotype-based advice does not motivate or promote greater behaviour change to reduce the risk of obesity, T2D and CVD, compared to non-genotype-based advice or general advice. However, recommendations are made for health care professionals and researchers to tailor genotype-based advice for young adults based on the findings of our survey. Finally, the effectiveness of the recommendations to motivate and change behaviour using genotype-based advice should be investigated in an intervention study in a young adult population.