The authors describe on examples from the practice of a genetic clinic seven different genetic syndromes associated with obesity: Laurence-Moon-Biedl, Alström, Weiss, Cohen, Carpenter, Prader-Willi and syndrome of insulin resistance. The autosomal recessive determination of the majority of these syndromes emphasizes their genetic impact with a high risk of repeated occurrence in the family. Visual and hearing defects increase clinical and social importance of these syndromes. When evaluating the genetic prognosis of risk families, the authors consider the possibility of prenatal diagnosis and its forms and the risk of implementation of a preventive method. In some instances obesity is a manifestation of a disorder of insulin receptors.