Stability of physical activity, fitness components and diet quality indices

Regular physical activity (PA), a high level of fitness and a high diet quality are positively associated with health. However, information about stability of fitness components and diet quality indices is limited. This study aimed to evaluate stability of those parameters.

This study includes 652 adults (men=57.56 (10.28) years; women=55.90 (8.34) years at follow-up) who participated in 2002-2004 and returned for follow-up at the Policy Research Centre Leuven in 2012-2014. Minutes sport per day and Physical activity level (PAL) were calculated from the Flemish Physical Activity Computerized Questionnaire. Cardiorespiratory fitness (CRF), morphological fitness (MORF; body mass index and waist circumference) and metabolic fitness (METF) (blood cholesterol and triglycerides) were used as fitness components. Diet quality indices (Healthy Eating Index-2010 (HEI), Diet Quality Index (DQI), Mediterranean Diet Score (MDS)) were calculated from a diet record. Tracking coefficients were calculated using Pearson/Spearman correlation coefficients (r_Pearson) and intra-class correlation coefficients (r_ICC).

In both men (r_Pearson&ICC=0.51) and women (r_Pearson=0.62 and r_ICC=0.60) PAL showed good stability, while minutes sport remained stable in women (r_Pearson&ICC=0.57) but less in men (r_Pearson&ICC=0.45). Most fitness components remained stable (r⩾0.50) except some METF components in women. In general the diet quality indices and their components were unstable (r<0.50).

PAL and the majority of the fitness components remained stable, while diet quality was unstable over 10 years. For unstable parameters such as diet quality measurements are needed at both time points in prospective research.