Definitions of night eating in adolescent girls

To describe the prevalence of night eating in a community cohort of black and white girls, using different definitions of night eating as described in the literature.

Three-day food diaries collected as part of the National Growth and Health Study were examined to identify episodes of night eating, which was defined in five different ways: eating >25% of daily caloric intake after the last evening meal, eating >25% of daily caloric intake after 7 pm, eating >50% of daily caloric intake after the last evening meal, eating >50% of daily caloric intake after 7 pm, or eating between 11 pm and 4:59 am.

Frequency of night eating varied tremendously depending on how the behavior was defined. For the least restrictive definition (>25% of total intake after last meal), 50% to 70% of girls reported one night eating event; for the most restrictive (>50% of total intake after last meal), only 1.5% of 11-year-old girls' diaries and 3.5% of 19-year-old girls' diaries contained a night eating event. The frequency of night eating decreased dramatically (typically by a factor of 10) if the inclusion criteria required multiple night eating events in a given week.

A standard definition of night eating behavior is needed to advance the field. An agreed-on operationalized definition that includes time of day, amount of calories consumed, and a frequency criterion would enable cross-study comparisons and encourage the examination of developmental and clinical considerations of night eating behavior.