Adiposity is a chronic disease that must be treated from childhood. Despite the transcendence of improving habits, few interventions report their contribution to decreasing adiposity. Methods: This cohort enrolled children and teens of any gender, 8–18 years old, and with a body mass index (BMI) z-score of ≥1 into “Sacbe”, a comprehensive program to identify which eating habits could reduce BMI z-score. The sample size calculated was 110 participants. We recorded anthropometric measures, clinical history, and habits. A clinically relevant reduction in BMI z-score was defined as ≥0.5 over 12 months or its equivalent according to the months of follow-up. Results: 58.2% were female, the median age was 12 years (range: 9.1–14.7), and the mean BMI z-score was 2.30 ± 0.83. The 82.7% achieved a reduced BMI z-score but 41.8% achieved a clinically relevant reduction with a median follow-up of 6.7 months. Eating out less than once per week was associated with this outcome, even after adjusting for energy intake, other eating patterns, sedentary screen time, physical activity, sleep duration, and sitting time (HR 2.12; 95% CI: 1.07–4.21). Conclusions: Eating out < once/week implicates less processed food exposition and better quality of food; this habit could be the most effective to reduce childhood adiposity.