To assess tracking of energy and nutrient intakes between adolescence and young adulthood.

Longitudinal study of a random sample of adolescents (aged 15 years at baseline). The extent of tracking of dietary intakes (assessed by diet history) was investigated using weighted kappa statistics (κ).

Northern Ireland population survey.

Adolescents who participated in the Young Hearts Project, Northern Ireland at age 15 years, and subsequently at young adulthood aged between 20 and 25 years (n = 245 males, n = 231 females).

Despite overall increases in height and weight (both P < 0.001), increases in body mass index in males (P < 0.001) and body fatness in females (P < 0.001), median reported intakes of energy (kJ kg− 1 day− 1), carbohydrate (g day− 1) and fat (g day− 1) decreased (all P < 0.001) over time. Expressed as nutrient densities (per MJ), diets at young adulthood were overall richer in thiamin, vitamin B6, total folate (all P < 0.001), vitamin C (P < 0.01) and vitamin D (P < 0.05). Whereas the nutrient density of the males' diets decreased over time for calcium (P < 0.05) and vitamin A (P < 0.001), iron and riboflavin densities increased in the females' diet (P < 0.001). Tracking of energy (MJ day− 1) and nutrient intakes (expressed per MJ day− 1) at the individual level was only poor to fair (all κ < 0.25), indicating substantial drift of subjects between the low, medium and high classes of intake with increasing age.

These data suggest that individual dietary patterns exhibited at 15 years of age are unlikely to be predictive of dietary intakes at young adulthood.