Dietary patterns and change in eating habits are influenced by multiple factors from an individual’s internal and external environment. A longitudinal dietary survey study provided quantitative evidence of dietary change and investigated factors influencing dietary change from adolescence to adulthood, using sociodemographic data and participants’ own perceptions of, and attributions for, their dietary change. Longitudinal dietary data were obtained in 1980 and 2000 (average age 11.6 and 32.5 years, respectively). Two questionnaires (2000) and 2 x 3-day food diaries (1980 and 2000) were collected from 198 participants. Foods consumed were assigned to one of the five food groups from The Balance of Good Health (a UK food guide). Questionnaire responses were used to examine how subjects perceived their own dietary change and the factors to which they attributed such change. Six key factors were identified from the questionnaire: parents, partners, children, nutritional awareness, employment and lack of time. Demographic and key factors were associated with degree of change in intake. The complex process of change in food consumption can be linked with an individual’s attributions for change.