Obesity is currently an increasing public health burden due to its related metabolic and cardiovascular complications. In Western countries, a significant number of people are overweight or obese, and this trend is, unfortunately, becoming increasingly common even among the pediatric population. In this narrative review, we analyzed the role of nutrition during growth and its impact on the risk of developing metabolic syndrome and cardiovascular complications later in life. An impactful role in determining the phenotypic characteristics of the offspring is the parental diet carried out before conception. During intrauterine growth, the main risk factors are represented by an unbalanced maternal diet, excessive gestational weight gain, and impaired glycemic status. Breastfeeding, on the other hand, has many beneficial effects, but at the same time the quality of breast milk may be modified if maternal overweight or obesity subsists. Complementary feeding is likewise pivotal because an early introduction before 4 months of age and a high protein intake contribute to weight gain later. Knowledge of these mechanisms may allow early modification of risk factors by implementing targeted preventive strategies.