High-Protein Meal Replacement Intervention in Overweight and Obese Career Firefighters: A Cluster Randomized Controlled Trial.

PURPOSE: The purpose of this cluster randomized controlled trial was to examine the effectiveness of a 14-week high-protein meal replacement (MRP) intervention on macronutrient intake, body composition, cardiometabolic health, and stair climb (SC) performance in career firefighters with overweight and obesity, and collect acceptability data to inform implementation efforts. METHODS: Twenty-six fire stations (51 firefighters; 36.7±7.3yrs; 33.1±4.8kg·m -2) were randomized to a MRP or wait-list control (CON) group. The MRP group consumed one shake/day (week 1) and two shakes/day (weeks 2-14) ad libitum. The primary outcome was percent body fat (%BF) measured by dual-energy x-ray absorptiometry, and secondary outcomes included macronutrient intake, body mass (BM), body mass index (BMI), regional fat distribution, resting heart rate (RHR) and blood pressure (BP), blood lipids, a weighted and timed SC task, and HR recovery (HRrec) following the SC task. Intervention acceptability was assessed in the MRP group. Linear mixed models assessed intervention effects with an alpha level set at 0.05. RESULTS: The MRP group improved %BF (-1.0 [-1.9, -0.06]; P=0.038) and secondary outcomes including dietary intake [increase in protein and fiber intake (P≤0.044); decrease in the CHO:PRO ratio (P=0.008)], body composition [BM, BMI, trunk fat mass (FM), and android:gynoid and trunk:limb %BF ratios (P≤0.026)], and SC HRrec (P<0.001). The MRP intervention had no significant effects on total calories, fat intake, lean mass, limb FM, RHR and BP, blood lipids, or SC time (P=0.135-0.985). Shake adherence was high (90.7±11.8%) and firefighters reported the intervention was convenient and they would continue long-term. CONCLUSIONS: The MRP intervention improved macronutrient intake, body composition, and SC HRrec and was well accepted, supporting a practical nutritional strategy to improve health in firefighters with overweight and obesity.