The fundamental cause of weight-related problems, from obesity to anorexia, is an imbalance between calories consumed and calories expended. The "nutritional status" concept embraces more than food-intake. It elucidates the dynamics between supply, demand and factors that affect metabolism, energy balance and energy expenditure. In recent years, major changes in the spatial-temporal structures of everyday life that could be possible contributors to weight-related issues of adolescents have emerged. A modern life style of low activity, irregular meal times, late-night food intake, stress and sleep deprivation possibly leads to a disturbed regulation of food intake which further can generate physical and/or psychological illnesses. Traditional studies of eating behavior use food diaries focusing on the average intake of energy and nutrients (e.g. Bellisle et al., 2003). Such methods are demanding for the respondent and require details about consumed amounts. A "Meal Matrix" (Lennernas & Andersson, 1999) has been used in studies of several different Swedish cohorts (e.g. Wissing et al., 2000). The Meal Matrix consists of seven food categories and eight different meal "types". Categorization is based on visible properties (food types) but at the same time reflecting invisible properties (nutrients). In the present study the Meal Matrix was developed further to be used as part of a questionnaire in a study of eating behaviors in 1281 adolescents between 12 and 17 years old in a southern Swedish municipality. Meal patterns in adolescents were assessed in relation to time of day for intake, sleep and physical activity. The aim of the study was to 1) test a self-report concept for food based classification of eating behaviors in adolescents, 2) to evaluate the nutritional quality of food and meals among them and 3) to get information about the rhythm of eating and slee-ping in relation to time of day and the biological clock.