A controlled weight loss intervention study among women of Somali background in Norway

•An intervention study developed in collaboration with Somali user representatives.•Women-only, female instructors, and the use of the Norwegian and Somali languages.•Emphasis on lifestyle change through self-empowerment and self-efficacy.•Modest non-significant effect on weight change after 12 months.•Further studies should be of longer duration. Women of Somali background in Norway have a high prevalence of overweight and obesity, compared with women in the general Norwegian population. For lifestyle interventions to be applicable for immigrants to Norway, it is important to culturally tailor interventions in collaboration with relevant communities. The primary outcome was a difference in weight change between the intervention and control groups. In this interventional study, Somali women living in one borough of Oslo Municipality in Norway with body mass index (BMI) ≥27.0 kg.m-2 received a co-created, culturally tailored 12-month weight loss intervention consisting of 24 interactive sessions during the first three months, and monthly sessions for the next nine months, compared to a control group. Both groups were measured at baseline and 12 months. A total of 169 participants were recruited, and 101 participants completed the follow-up. After multiple imputation, the mean difference in weight change adjusted for baseline weight, age, education, employment, marital status, number of children in the household and length of Norwegian residency was -1.6 kg (95 % CI -3.57, 0.43, p = 0.12) in the intervention compared to the control group. This culturally tailored intervention study demonstrated a modest non-significant effect on weight change after 12 months, possibly due to the short intervention duration and COVID-19. Further studies of a longer duration and considering the provision of childcare are needed to understand whether this approach can be transferred to other immigrant groups and genders. Trial registration: The study was registered at clinicaltrials.gov NCT04578067, 2020-09-29. [Display omitted]