Obesity is a worldwide health problem affecting developed and developing nations. Botswana is an upper-middle income nation experiencing rapid urbanization, economic, and nutritional change. The combined prevalence of adolescent overweight and obesity has now surpassed underweight. Little is known regarding the adolescent and adult perceptions of adolescent diet, physical activity, body size, the meaning of obesity, and obesity prevention interventions. This qualitative-descriptive study uses Ecological Systems Theory to analyze and interpret data from 15 focus groups (12 adolescent and 3 parent focus groups of unrelated participants) conducted in Gaborone, Botswana. The purpose of this study is to describe the factors that influence adolescent and adult perceptions and attitudes related to adolescent diet, physical activity, body size, obesity and potential obesity interventions. Prolonged data immersion, clustering of analogous data into themes, and direct reporting of participant voices were used to provide a rich description of the shared experiences and perceptions of the study participants. Results indicate that adolescents identify healthy versus unhealthy foods, yet choose unhealthy foods based on taste preferences, social pressures, and the perceived affordability of unhealthy foods. Parents prefer a healthy diet for their adolescent children, although they acknowledge purchasing unhealthy foods for their children based on adolescent taste preferences and social pressures. Adolescent and parent participants suggest a body size analogous to normal weight is most desirable for adolescents themselves and most attractive in the opposite sex. Obese body sizes are associated with perceived laziness, isolation, and negative social stigma. Additionally westernized preferences are replacing the historical notion that a large body size is consistent with wealth, strength, and prosperity. Participants also perceive thinness to be related to illness, specifically suspected HIV infection due to the relatively high prevalence of HIV infection in Botswana. Adolescents and parents of adolescents show a willingness to participate in obesity prevention programs. Participants suggest that any school-based program be voluntary, entertaining, informative, involve parents, take into consideration peer influence, and increase healthy food offerings while not eliminating individual choice. An ecological, school-based obesity prevention program with parent involvement should be developed for this adolescent population.