Body Composition of Obese Subjects by Air Displacement Plethysmography: The Influence of Hydration

Abstract

Abstract2 ) entered the ADP chamber without and with oil (1, 2, or 4 liters), water (1, 2, or 4 liters), or mixed (1 liter oil ϩ 1 liter water or 2 liters oil ϩ 2 liters water) loads. Real and measured changes in body composition were compared by regression analysis and Bland-Altman procedures. Results: The ADP-measured changes in volume did not differ from the real values and were strongly correlated with them (r ϭ 0.98). In all cases, loads of differing composition and similar volume led to different values of fat, fat-free mass, and percentage fat. Water was detected as increased fat-free mass only with loads of Ն2 liters, most of the water being falsely detected as increased fat mass. The observed changes were correlated with the real ones for fat mass (r ϭ 0.68; p Ͻ 0.0001), fat-free mass (r ϭ 0.66; p Ͻ 0.0001), and percentage fat (r ϭ 0.61; p Ͻ 0.0001), but fat mass changes were overestimated by ϳ1 kg, and fat-free mass changes were underestimated by ϳ1 kg. This underestimation increased with the highest water loads, as shown by the Bland-Altman plot (r ϭ Ϫ0.27; p Ͻ 0.05). Percentage fat changes were overestimated by 0.8% (p Ͻ 0.001); the magnitude of the error was correlated with the weight of the water load (r ϭ 0.62; p Ͻ 0.0001). Discussion: ADP accurately measures changes in body volume, discriminating small changes in body composition. It overestimates changes in adiposity, as most of the increased hydration is detected as an enlarged fat mass.

Influence of Changes in Body Composition and Adaptive Thermogenesis on the Difference between Measured and Predicted Weight Loss in Obese Women

“…However, increased hydration of FFM in obesity might lead to an overestimation of FM. If hydration of FFM decreases with weight loss, this would lead to an overestimation of losses in FM [24]. A second limitation of the study was the assumption of a low activity level (PAL 1.5) for 10 patients with missing step count data.…”

Insulin Therapy and Body Weight, Body Composition and Muscular Strength in Patients with Type 2 Diabetes Mellitus

“…Air displacement plethysmography is a new, safe, quick, and valid technique, providing accurate measurements of body density [6] and discriminating moderate changes in FM and FFM [7]. Although some uncertainties due to the hydration of FFM may influence any two-compartment model-based analysis [8], the simultaneous measurement of muscle strength (MS) by dynamometry can be used to confirm the results of FFM: a correlation between FFM and MS has been previously demonstrated [9–11] …”

Métodos indiretos para mensuração da gordura corporal em adolescentes escolares

“…As duas técnicas de avaliação empregadas no presente estudo não se relacionam diretamente pela forma diferente com que mensuram a gordura corporal, entretanto, diversos estudos têm mostrado uma forte correlação entre os resultados (5,7,(22)(23)(24)(25) , trazendo uma alternativa eficiente para o diagnóstico e acompanhamento do excesso de peso relacionado ao acúmulo de tecido adiposo, especialmente em crianças e adolescentes (26) . A pletismografia com deslocamento de ar é outro método para detecção da composição corporal que pode ser considerado fidedigno, rápido (3 a 5 minutos por teste) e de fácil aplicação (28) , por demandar menor necessidade de cooperação do avaliado. Porém, assim como a BIA, pode superestimar a adiposidade em casos de hiperhidratação (1,5,9,28) .…”

“…A pletismografia com deslocamento de ar é outro método para detecção da composição corporal que pode ser considerado fidedigno, rápido (3 a 5 minutos por teste) e de fácil aplicação (28) , por demandar menor necessidade de cooperação do avaliado. Porém, assim como a BIA, pode superestimar a adiposidade em casos de hiperhidratação (1,5,9,28) . Por isso, recomenda-se fortemente que o avaliado siga a padronização do teste (17) e mantenha a ingestão normal de líquidos (boa hidratação) no dia da avaliação.…”