This qualitative study explores the structural barriers to preventive interventions targeting childhood obesity in the Danish health care system. Based on interviews with relevant health care professionals, the paper reports on the problems which are experienced by general practitioners and health visitors and which complicate implementation of the policies of the Danish health authorities. Findings show that the current system is not well equipped to treat early overweight. A gap in primary preventive health care for children at age 3–5, indistinct lines of responsibility, inadequate cooperation, and lack of resources together make it difficult for health care professionals to initiate interventions and reach the children in need of support. By analyzing the policy implementation process in a theoretical framework that discloses the discursive allocation of responsibilities, the study is able to provide a deeper description and analysis of the problem. The study makes it clear how preventive health care for overweight children rests on the negotiation of formal and performed responsibilities among health practitioners within a framework of scarce resources and communication deficit.