Breakfast skipping and body mass index among adolescents in Greece: whether an association exists depends on how breakfast skipping is defined.

Many studies have found an association between breakfast skipping and either body mass index (BMI; calculated as kg/m(2)) or overweight/obesity among adolescents, but several studies have found no association. This cross-sectional study investigated the hypothesis that this discrepancy is partly due to three differences in methodology. First, some studies have examined BMI, but other studies have examined overweight/obesity. Second, some studies have controlled for potential confounders, but other studies have not. Third, different studies have used different definitions of breakfast skipping. This study examined both the relationship between breakfast skipping and BMI and the relationship between breakfast skipping and overweight/obesity, compared unadjusted results with results adjusted for potential confounders, and compared results for 24 definitions of breakfast skipping. The sample consisted of 811 students at high schools in Piraeus, Greece, who completed a questionnaire and had their height and weight measured. The results supported this hypothesis. First, fewer breakfast-skipping variables were associated with BMI than with overweight/obesity. Second, fewer associations were found when controlling than when not controlling for potential confounders. Third, fewer associations were found for variables corresponding to some definitions of breakfast skipping than for variables corresponding to other definitions.