On 5 and 6 April 1991, at the National Research Council (CNR) in Rome, a Consensus Conference on the relationship between overweight, obesity and health was held. The conference was sponsored by FATMA (Applied Project on Disease Factors of the CNR) and UICO (Italian Society for the Study of Obesity) with the purpose of establishing guidelines for health employees. The development of the conference followed the methodology set down by OMAR to obtain a rational and significant consensus on the answers to six basic questions prepared by the planning committee. The questions were the pivotal point of the conference and were brought to the attention of all the attendees and widely diffused among the medical community; they were proposed with the aim of giving an exhaustive definition of obesity, to investigate its relationship with mortality and morbidity, to highlight its social characterization, to indicate methods of evaluation and recommendations for weight loss, to select groups at risk, and to focus general guidelines for research. After the presentation of the state of the art on 18 topics by experts in the field, the 22 members of the consensus panel, impartial experts from a vast area of the scientific community, discussed a draft document representing the answers to the questions, which was subsequently submitted to the 307 attendees, discussed and then approved. This paper is the definitive document of the Consensus Conference. The introduction explains the reasons which led to the decision to promote the conference six years after the one held in the United States. The methodology is then set out. The questions are answered in the form of recommendations and backed up by data and scientific evidence from the literature.