Introduction The effect of the day of the week on nutrient intake on the overall consumption, collected by short reports, was notorious. However, it is still unknown for macronutrient intake collected by the food frequency questionnaire (FFQ).

Objective To evaluate the effect of data collect during the beginning and end of the week on macronutrient intake in data from FFQ applied in adolescents from southern Brazil.

Methods A cross-sectional study investigated a population-based sample of 136 adolescents, aged 11–19 years. Dietary data were obtained by FFQ. Macronutrients intake was aggregated into Monday to Wednesday or Thursday to Saturday. The analysis were carried out for the overall sample and stratified by sex using the Mixed Linear Model and the effect of age and gender was tested.

Results The macronutrient intake varied according the week phase. The analysis of the overall sample showed increasing consumption from the beginning to the end of the week for all macronutrients. However, the increased macronutrient consumption occurred at expenses of women's intake and the difference on intake was 482.64 kcal/day; p=0.010; 61.16 g/day; p=0.019; 11.53 g/day; p=0.014; and 22.76 g/day; p=0.010; for energy, carbohydrate, protein and total fat, respectively, for the end of the week.

Conclusion These results show that adolescents have increasing consumption of macronutrient during the week, reaching the highest intake at the end of week.