A survey of opinions on the causes of and effectiveness for treatment of obesity was carried out on data provided by questionnaires from 57 physicians and scientists involved in obesity research. Responses were grouped by region (Europe, North America, and South America), gender, age (30-50 and over 50 years), and professional training (MD or PhD). Metabolic factors were considered the most important cause of obesity overall with physical inactivity only slightly behind. There were no gender differences, but the older group thought physical inactivity was a more important cause than the younger group. Weight cycling overall was not considered very important, although it was significantly more important among the Ph.D. group. Low-fat diets were considered the most effective treatment, with the older group of respondents rating low-fat diet more highly than their younger colleagues. Exercise was viewed as a more important treatment among North Americans, and medications as less in the treatment of obesity. All groups viewed serotonergic and thermogenic drugs as the most effective treatments whose usefulness would increase during the next 10 years.