Introduction: At one year of age, factors that favor the development of obesity and other metabolic disorders in later stages of life are present. Objective: To identify perinatal, societal, and dietary risk factors for excess weight and obesity in 12 months infants. Subjects and methods: Case-control studies with infants under the care of Family Medicine Units. These cases studied were overweight or obese children, and control cases were children at a healthy weight. Each group included 152 infants, who were evaluated based on their responses to a questionnaire, their records, and perinatal, societal, and dietary variables. Results: The variables with statistical significance were high pre-gestational weight, high gestational weight gain (OR 1.79-3.88), absence of breastfeeding and exclusive formula feeding (OR 2.02 and 1.75). Conclusion: In the presence of pre-pregnancy obesity and exclusive formula feeding, there is a 64.4% greater risk of becoming overweight or obese at 12 months old.