The literature review is devoted to modern ideas about the genetic and epigenetic factors of the formation of obesity and concomitant complications in boys. Risk factors for overweight are prepubertal age, male sex, and urban environment. Initial signs of metabolic disorders appear already in childhood and are more often recognized in children with excess body weight and family history. Increased body mass index in late pubertal is strongly associated with cardiovascular mortality (in young adults or in adulthood). Genetic factors for the development of obesity are family history of obesity, type 2 diabetes, hypertension, and adverse genotypes; epigenetic factors are diet pattern, level of physical activity, metabolic disorders in mother, etc. Encouraging higher levels of physical activity and less sedentary behavior may mitigate the effect of risk alleles on genetic predisposition to obesity. It was revealed that the development of severe forms of obesity is associated with an increased prevalence of metabolic and cardiovascular risk factors, especially among boys and young men. The presence of obesity and its progression are independent risk factors for cardiometabolic disorders in boys. An important role in the prevention and treatment of obesity in childhood and adolescence belongs to formation of a conscious attitude to health. The development of individual programs taking into account the presence of unfavorable genotypes and correction of the epigenome will significantly improve the system of obesity prevention at earlier age periods, will prevent or delay the manifestation of complications in adulthood.