Objective: To evaluate changes in food intake after adolescents attended a food and nutrition education program at a non-profit institution. Methods: Fifty-four adolescents aged 16 to 19 years, of low socioeconomic level, enrolled in an non-governmental organization in São Paulo, underwent a nutritional intervention of six months consisting of six meetings with dieticians, as well as strategic communication and relationship actions. Body weight, height, body mass index, questionnaire on knowledge on nutrition and feeding practices, 24-hour recall, and diet quality assessment using the Diet Quality Index associated with the Digital Food Guide were collected at baseline and after the intervention. Dietary pattern improvement was defined as an increase of at least 5 points in Diet Quality Index associated with the Digital Food Guide. Results: Understanding of food labels increased, and the dietary patterns on weekdays and weekends improved by 33 and 37%, respectively. The intake of legumes, milk, dairy products, fruits, and vegetables increased (adequacy components). However, intakes of nuts and whole grains were low, and intake of moderation components was high. Conclusion: The program improved the dietary patterns of adolescents, making it a viable and inexpensive method to prevent disease and improve health and quality of life. In addition, the Diet Quality Index associated with the Digital Food Guide has proven to be a good nutritional tool for assessing changes in food intake and for guiding future counseling and nutritional intervention actions for this population.