The aim of this study was to examine the reliability of the Spanish version of Composite Scale of Morningness (CSM) and its ability to measure the circadian typology.

Voluntary and unpaid psychology students (N = 391; 132 men and 259 women), aged between 17 and 33, completed the questionnaire between the months of September and December.

The total score was independent of age and gender, with a close to normal distribution and a non-significant negative skewness. The internal consistency was high (Cronbach’s α = 0.87) and factor analysis extracted three factors labeled Time of Retiring (items 2 and 7), Activity Planning (items 8, 9, and 13) and Morning Affect (items 3–6, and 10–12). With the 10th and 90th percentiles as cut-off scores, scorers below 22 (N = 40; 10.2%) are classified as evening-types and scorers above 39 as morning-types (N = 28; 7.2%).

The Spanish questionnaire shares most of the good psychometric properties of other versions of the CSM, and thus can be used for Spanish-speaking student samples. Nevertheless, further studies of normative data in workers and aged subjects are needed in order to validate CSM.

To experimentally compare the effects of eating or skipping breakfast on energy expenditure, activity levels and dietary habits.

A randomised cross-over trial, lasting 2 weeks. Participants were provided breakfast during one week and were required to fast until mid-day during the other week.

University campus.

Forty-nine participants (twenty-six female and twenty-three male participants) were recruited. Food intake was monitored using food diaries, and energy expenditure was assessed using pedometers and heart rate monitors. Morningness–eveningness, physical activity and health were assessed using validated questionnaires.

Across all participants, daily energy expenditure did not differ between the two experimental conditions. Total energy intake over 24 h did not vary with condition (male participants: 8134 (sd 447) kJ/d and 7514 (sd 368) kJ/d; female participants: 7778 (sd 410) kJ/d and 7531 (sd 535) kJ/d, for the breakfast and no-breakfast conditions, respectively). However, when comparing habitual breakfast eaters with those with irregular or breakfast-skipping habits, it was found that male non-habitual breakfast eaters consumed significantly (P = 0·029) more energy during the breakfast condition. Furthermore, female participants who were habitual breakfast eaters were found to eat significantly (P = 0·005) more and later in the day under the no-breakfast condition.

Although the suggestion that breakfast is a behavioural marker for appropriate dietary and physical activity patterns is not refuted by the present findings, our data suggest that the effect of breakfast may vary as a function of gender and morning eating habits, and thus there may be other mechanisms that link BMI and breakfast consumption behaviour.