Dietary patterns and young adult body mass change: A 9-year longitudinal study

Purpose While excessive weight gain is highest during young adulthood, the extent to which specific dietary patterns are associated with changes in measures of body mass in this course of life remains unknown. We aimed to examine the associations of dietary patterns at 21 years with changes in body weight and body mass index (BMI) between 21 and 30 years. Methods We used data on young adults from a long-running birth cohort in Australia. Western and prudent dietary patterns were identified applying principal component analysis to 33 food groups obtained by a food frequency questionnaire at 21 years. Body weight and height were measured at 21 and 30 years. Multivariable regression models, using generalized estimating equations, were adjusted for concurrent changes in sociodemographic and lifestyle variables in evaluating the effect of identified dietary patterns on changes in weight and BMI over time. Results In the fully adjusted model, young adults in the highest tertile of the Western pattern had a mean weight gain of 9.9 (95% CI 8.5, 11.3) kg compared to those in the lowest that had a mean weight gain of 7.1 (95% CI 5.6, 8.5) kg, P -for linear trend = 0.0015. The corresponding values for mean gains in BMI were 3.1 (95% CI 2.7, 3.6) kg/m 2 for young adults in the highest tertile compared to 2.4 (95% CI 1.9, 2.9) kg/m 2 for those in lowest, P- for linear trend = 0.0164. There was no evidence of a significant association between the prudent pattern and mean changes in each outcome over time in this study. Conclusions The findings of the current study show that greater adherence to the Western diet at 21 years was positively associated with increases in body weight and BMI from 21 to 30 years of age, whereas the prudent diet had no significant association with these outcomes. The findings provide evidence that the adverse effects of the Western diet on weight gain in young adulthood could partly be prevented through optimising diet in the early course of life.