In this longitudinal population-based study, adolescent drinking habits were only weakly associated with later body weight and weight gain from adolescence to adulthood. Women drinking less than monthly and abstinent men had a smaller weight gain during the follow-up and also smaller mean BMI at young adulthood (T4) than subjects drinking more often. Among women, weekly alcohol use was associated with greater adult waist circumference. The effect on waist became statistically non-significant after adjusting for confounding factors and was not at all seen among men. Also, the effect sizes were relatively small, approximating for example to a difference of 2.1 kg in body weight on a subject of 1.85 m in height between abstinent and monthly drinking men. Further, in our more detailed analyses using longitudinal data analyses, the results were ambiguous and mostly statistically insignificant after adjusting for confounding factors.
Our results differ somewhat from the previous studies. The cross-sectional association between BMI or overweight and alcohol drinking reported among Australian (Burke et al., 2001
) and Greek (Tzotzas et al., 2008
) adolescents was not seen in this study. However, in the Australian study, alcohol drinking data were gathered for only 2 days in the middle of the week, so the assessment ignored weekend drinking, and no detailed information on alcohol measures were given by Tzotzas et al. (2008)
We are aware of only three previous longitudinal studies concerning the association of adolescents' alcohol drinking and weight. The positive association between alcohol use and later obesity reported in the two studies using US samples (Fan et al., 2008
; Oesterle et al., 2004
) was not seen in our data which can be due to cultural differences. In the study by Fan et al. (2008)
, the lifetime alcohol use was retrospectively reported in middle-age or later, which is an effective way to gather information throughout the life-span but is subject to recall bias. Further, the subjects used were born before year 1961 and therefore, present different cohorts than in the current study. The other US study population used by Oesterle et al. (2004)
was born in the 70s like ours' but was ethnically more diverse and included a substantial proportion of low-income families (Oesterle et al., 2004
). As childhood social circumstances are known to predispose to later obesity and overweight (Power et al., 2003
), this may have affected their results. Alcohol consumption was measured as self-reported heavy episodic drinking, meaning minimum of five or more alcoholic drinks in a row (Oesterle et al., 2004
). Laitinen et al. (2004)
found self-reported alcohol use often at age 14 to be associated with later abdominal obesity only before adjusting for BMI and other confounding factors in the model. Our results are in line with this even if our subjects were born +AH4-10 years later. Alcohol use among Finnish adolescents increased from late 70s to 90s (Lintonen et al., 2000a
). Since then, it has been relatively stable, and therefore, it can be assumed that these results are applicable to the present situation. Alcohol consumption among Finnish adolescents is currently slightly below the European average (Hibell et al., 2004
; Lintonen, 2005
), and it is possible that the effect of alcohol on body weight differs according to heavier consumption in other European countries.
The never-drinking males and less than weekly drinking females had a smaller weight gain than the others, but the lack of dose-dependence would suggest that the larger weight gain is not necessarily caused by the energy addition due to alcohol in their diet. It is possible that some of the differences seen in weight gain of groups having different drinking habits are caused by differences in other factors such as eating behavior or physical activity associated with alcohol drinking. The results of the multilevel models and regression models examining the relation of drinking frequencies or binge drinking to weight gain or waist circumference also suggest that the overall association between drinking and body weight is quite weak, or it could be due to instability of the drinking habits in adolescence.
The strengths of this study include the longitudinal design, large sample size, repeated assessments of drinking habits, long follow-up time and large number of possible confounding factors, including parental BMI, taken into account. A possibility to assess dietary habits and amount and type of alcohol beverage more in detail would have further strengthened the study. Using only self-reported data is a certain weakness of our study, but taking into account the large sample size and multiple measures, it would be beyond realistic resources to get all data measured. In future studies, attention should be paid on more careful measurement of these issues (e.g. food frequency questionnaire or food and drinking diaries), though even these suffer from underreporting of total intake, especially among the overweight and obese (Heitmann and Lissner, 1995
) or heavy drinkers (Midanik, 1988