ObjectivesBackground: Overweight/obesity is a problem in Nigeria and roll out of treatment programmes at secondary health care level is a priority.Objective: This research aimed to compile a profile of behaviours and moderating factors for the development of a weight loss intervention. MethodsTwo groups of patients were recruited from outpatient clinics at secondary health care facilities. Group 1 (n = 328) completed a questionnaire on socio-demographics, medical history, body image, food choices and physical activity. Group 2 (n = 18) completed an in-depth interview on weight loss concepts/body image. Height and weight of both groups were measured. Six health care personnel were involved in key informant interviews. Quantitative data (QtD) were analysed with SPSS and in-depth interviews (qualitative = QID) with Nvivo. ResultsAbout 40% of survey respondents were overweight and 60% obese; 44.4% of in-depth interview respondents were overweight and 55.6% obese. Physical inactivity (55.8% inactive), low fruit/vegetable intake (consumed ≤ 2 times/day), high fat meat intake (consumed > 1 time/day) and large carbohydrate staple portions (consumed 2 times/day) were identified as key target behaviours (QtD). Moderating factors include underestimation of weight (QtD, QlD), satisfaction with current size although overweight/obese (QlD), co-morbidities and not obesity per se identified as problematic (QID), lack of insight in the role of physical inactivity (QlD), poor knowledge of healthy eating (QtD), too comfortable and relaxed, resulting in over-eating (QlD) and no control over body size (genes, God’s will) (QlD).From the health personnel perspective (three physicians, two matrons and one nutritionist) (QlD), only few recognised obesity as a disease. Obesity was not routinely screened for except it is obvious, partly due to lack of tools/skills. Lifestyle modification was mentioned as treatment but only the context of treatment of hypertension and type 2 diabetes mellitus. ConclusionsConsiderations for intervention development are poor food choices, physical inactivity, satisfaction with a large body size and not recognising obesity as such and lack of understanding of causes of obesity. Funding SourcesPostgraduate Academic Mobility for African Physician Scientists (PAMAPS), EU-PhD sponsorship.