An individual setup of the CooL-intervention for overweight or obese people who fit less in a group setting: a mixed method study

Background: CooL (Coaching on Lifestyle) is a two-year group-based lifestyle intervention for individuals with overweight or obesity, aimed at supporting behaviour change and improving health outcomes (e.g., enhanced quality of life and weight reduction). While the intervention is covered by Dutch basic health insurance and therefore widely available, the group format is not suitable for everyone, for example for individuals with chronic mental or personality-related problems. This prompted a pilot study to examine the added value of an individual version, CooL one-to-one for people who experience limited fit within a group setting, alongside the regular group-based CooL program, and to identify improvements for broader implementation in the Netherlands. Data were collected between November 2022 and December 2024 from adults living in the southern region of the Netherlands. Methods: Quantitative data were obtained at baseline (T0) and after eight months (T1) on anthropometrics, perceived control and support, physical activity, diet attentiveness, alcohol use, smoking, perceived fitness, sleep, and stress (n=39). Changes over time were analyzed using paired t-tests comparing T1 to T0, with Cohen’s d calculated as an effect size measure. Qualitative data on experiences, barriers, and facilitators were collected through interviews with participants (n=11), coaches (n=5), and stakeholders (n=11) during the intervention period. Results: Behaviour change among people who experience limited fit within a group setting is demanding and requires flexibility and additional effort from participants, coaches, and stakeholders. Despite the complex circumstances of the participants, all measured indicators showed improvements in the desired direction. More intensive collaboration with other healthcare providers and social workers seems essential to effectively support behaviour change in this population. Conclusion: CooL one-to-one offers added value through 1-to-1 sessions for individuals who do not fit within a group. Although this version of CooL requires additional effort from all parties involved, the overall satisfaction is high, the changes over time in terms of health and related outcomes are promising and there is clear potential for further development. Trial registration : Dutch Trial Register NTRNL6061 (on 13-January-2017). Registered at Overview of Medical Research in the Netherlands (OMON), via https://www.onderzoekmetmensen.nl/