Effects of a powdered meal replacement on body composition in individuals with excess body weight: Comparison across...

Accurate detection of body composition changes is essential for evaluating nutritional interventions. In a previous 12-wk randomized controlled trial, adults with excess body weight who consumed a powdered meal replacement (PMR) under weight-stable conditions increased lean soft tissue assessed by dual-energy x-ray absorptiometry. This secondary analysis evaluated whether comparable changes were detected using other body composition techniques and whether hydration-related variation impacted tracking of fat-free mass (FFM) and related compartments. We hypothesized that multiple techniques would detect increases in FFM and hydration markers. Participants (n = 63) were randomized to either a PMR group, which added PMR twice daily to their usual diet, or a control group, which maintained their usual diet. Body composition was assessed using dual-energy x-ray absorptiometry, bioelectrical impedance analysis, air-displacement plethysmography (ADP), and an adapted 4-compartment (4C) model. Changes (95% confidence intervals) in the PMR group from baseline to week 12, compared with the control group, included increases in ADP-derived FFM (1.31 [0.51; 2.12] kg, P < 0.001), 4C-derived FFM (1.01 [0.25; 1.78] kg, P = 0.002), and total body protein (TBpro: 0.60 [0.14; 1.07] kg, P = 0.007). No significant changes were observed in fat mass or hydration-related compartments. In sex-stratified analysis, the PMR group increased ADP-derived FFM among males (1.70 [0.28; 3.12] kg, P = 0.021) and females (1.12 [0.05; 2.18] kg, P = 0.031). Overall, ADP was the most sensitive method for detecting longitudinal changes and performed comparably to the 4C model. Increases in FFM and TBpro appeared independent of hydration changes, suggesting true accretion of metabolically active tissue, likely muscle mass.