Keep it CooL! Results of a two-year CooL-intervention: a descriptive case series study

Coaching on Lifestyle (CooL) is a two-year healthcare intervention for people with overweight or obesity, stimulating weight reduction by promoting sustained healthier behavior. The objective of this study is to investigate the effects of CooL on participants' anthropometrics, personal factors and behavioral factors over the two-year timeframe of CooL. A descriptive case series study, using a broad set of routinely collected data on anthropometrics, personal factors and behavioral factors of adults living across the Netherlands. The data were collected between November 2018 and December 2021 among participants of CooL (N = 746) at three moments during the intervention: at baseline (T0), at 8 months (T1) after completion of phase 1 and at 24 months (T2) after ending CooL. Changes over time were analyzed using paired t-tests comparing baseline to T1 and baseline to T2. In addition, potential differences on outcomes in subgroups based on education level, weight status and group size were examined using paired t-tests and ANOVA-tests. The results showed positive changes on all outcomes at 24 months compared to baseline. The largest effects were on perceived health, attentiveness towards meal size and meal composition (large effect size). Mean weight loss was 4.13 kg (SD 7.54), and mean waist circumference decreased with 4.37 centimeters (SD 8.59), indicating a medium to large effect size. Changes were consistent across subgroups varying in educational level, BMI at baseline and group size. The study demonstrated sustained weight-related effects of CooL over 24 months supporting its two-year duration. The results indicate that CooL, though not for every individual, is in general appropriate and effective for different group sizes and for a wide variety of participants regardless of level of education, or BMI at baseline. Dutch Trial Register NTRNL6061 (13-01-2017). Registered at Overview of Medical Research in the Netherlands (OMON), via https://www.onderzoekmetmensen.nl/ .