Purpose – This paper aims to evaluate the effects of a school-based obesity prevention program targeting Brazilian adolescent girls on dietary intake and meal frequency. Design/methodology/approach – It was a six-month school-based group randomized controlled trial with female adolescents. The intervention was based on the Social Cognitive Theory and focused on ten nutrition and physical activity key messages. Diet intake was measured using a validated food frequency questionnaire, and the food items were aggregate into the eight food groups of the Brazilian Food Guide Pyramid. The meals frequency assessed were breakfast, lunch, dinner and snack-in-between-meals, the frequency ranged from never to everyday. Linear mixed models were used to examine the dietary effects and chi-squared test to identify proportional differences among groups in meal frequency. All analyses followed intention-to-treat principles and alpha levels of p ≤ 0.05 were set. Findings – After six months from baseline, changes in the fruits (mean [SE] 12.48 kcal [7.86], p = 0.005), vegetables (8.80 kcal [7.11], p = 0.006) and sugar (−55.98 kcal [50.70], p = 0.036) groups were demonstrated. Proportional difference was shown for snack-in-between-meals (p = 0.001), and the frequency most cited was for “five to six days” per week. Originality/value – The “Healthy Habits, Healthy Girls-Brazil” showed promise in the adolescents’ dietary intake and could be used as framework for future interventions. Also, the methods used for dietary intake can be enhanced and implemented for future studies.