HAPpEN: A pragmatic general practitioner-centered obesity management trial in rural Germany integrating multimodal lifestyle interventions

Background: Elevated prevalence of obesity has increasingly challenged public health systems worldwide, with rural areas being particularly affected. This trial aimed to evaluate the effectiveness of a general practitioner (GP)-centered, multifactorial intervention for obesity management in rural areas. Methods: The HAPpEN trial was a pragmatic, controlled study conducted in six rural primary care practices in Upper Franconia, Germany, with 98 adults (BMI ≥30 kg/m²) enrolled and a 12-month follow-up rate of 62.2%. Exclusion criteria included severe comorbidities restricting physical activity. The intervention combined GP-led behavioral strategies, monthly motivational counselling, nutritional guidance, physical activity, educational workshops, and digital self-monitoring with community activities to foster engagement. The control group received standard care. Primary outcomes included body weight, body mass index (BMI), waist circumference, blood pressure, heart rate, and metabolic parameters such as hemoglobin A1c (HbA1c), fasting glucose, cholesterol, triglycerides, high- and low-density lipoprotein, C-reactive protein and uric acid. Results: The intervention group showed significant reductions in body weight (−5.0 ± 7.7 kg, 95% CI: [-7.24, - 2.83], p< 0.001) and BMI (−1.7 ± 2.6 kg/m², 95% CI: [-2.48, -0.99]), p< 0.001] over 12 months. Waist circumference (−11.5 ± 11.1 cm, 95% CI: [-15.57, -7.34], p< 0.001), systolic blood pressure (−8.3 ± 14.2 mmHg, 95% CI: [-13.22, -3.30], p= 0.04) and HbA1c levels (-3.3 ± 6.2 mmol/mol, 95% CI: [-5.33, -1.30], p< 0.001) significantly improved, with HbA1C normalizing in many cases. A negative correlation was identified between program engagement and weight loss (r _s = −0.453, p< 0.001). Conclusion: The GP-centered, multifactorial intervention significantly reduced body weight and improved metabolic health markers in individuals with obesity. Sustained program engagement correlated with enhanced weight loss, underscoring the importance of structured support in rural obesity management. These findings emphasize the key role of GPs in obesity care and suggest the potential for broader application. Trial registration : DRKS00033916, March, 20 ^th 2024 retrospectively registered.