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The primary purpose of this investigation was to compare estimations of percentage body fat (%fat) using air displacement plethysmography (ADP) and hydrostatic weighing (HW) in a heterogeneous (age and %fat) sample of the population. Of secondary importance was to determine whether there were differences between the two methods among lean (n = 32), average (n = 34) and overweight (n = 29) subsets of this sample. A total of 95 adults (men 27, women 68) ranging in age from 18-52 years volunteered for this study. Test-retest reliability for %fat ADP (n = 16) was 0.99 with a technical error of 0.75%fat and a coefficient of variation of 3.4%fat. Mean body density using ADP [1.048 (SD 0.016) g.ml-1] was not significantly different when compared to HW [1.049 (SD 0.017) g.ml-1], which corresponded to a non-significant difference in %fat [22.5 (SD 7.3)% ADP compared to 22.0 (SD 7.6)% HW]. Regression analysis provided the equation: %fat HW = 0.9121%fat ADP + 1.5123; r = 0.88, SEE = 3.6, which did not differ significantly from the line of identity. Data for the subsets revealed a significant overestimation of %fat ADP [16.4 (SD 4.8)%] compared to HW [14.1 (SD 3.2)%] (P = 0.001) for lean individuals while no difference was found in the average [21.9 (SD 4.4)%fat ADP compared to 22.0 (SD 3.4)%fat HW] or overweight [29.9 (SD 5.5)%fat ADP compared to 30.8 (SD 4.1)%fat HW] subsets. Measuring %fat by ADP is a highly reliable method and valid when compared to HW for a heterogeneous sample of adults. The ADP method requires little expertise to operate, is quick to perform, and may be more accommodating for certain individuals compared to HW. However, in this study ADP was less valid for lean individuals. Further investigation is warranted to determine the bias of this method for subsets of the population which may be outside the average range of %fat (men 15.4%-22.0%, women 18.4%-28.5%).

Morris hepatoma 7777 cells freshly isolated from highly malignant tumors grown in the hindlimb of buffalo rats actively convert ketone bodies to cholesterol and fatty acids. On the basis of results obtained with (-)-hydroxycitrate, an inhibitor of the ATP citrate lyase enzyme, the metabolic pathway for acetoacetate conversion to lipids is exclusively cytoplasmic, whereas that for 3-hydroxybutyrate involves both extra- and intramitochondrial compartments. Subcellular distribution studies indicated accumulation and compartmentation of 3-hydroxybutyryl CoA primarily in the cytoplasm of hepatoma cells incubated with either ketone body. In contrast, the compartmentation of acetoacetyl CoA is dependent on whether the substrate is acetoacetate or 3-hydroxybutyrate. With acetoacetate, the acetoacetyl CoA is entirely cytoplasmic, whereas with 3-hydroxybutyrate, it is equally divided between the intra- and extramitochondrial compartments. The results are discussed in terms of the known and proposed metabolic pathways for lipid synthesis from ketone bodies, particularly that from 3-hydroxybutyrate.

The purpose of this investigation was to examine the accuracy of percent body fat (%BF) estimates obtained by air displacement plethysmography (ADP) using the BOD POD Body Composition System compared with hydrostatic weighing (HW) in a group of female college athletes (n = 80). In addition, %BF estimates by skinfold measures (SF) were also obtained for comparison. A lean subset (n = 39) of the sample was also examined. Mean %BF estimated for the entire sample by ADP (21.2 +/- 5.9%) was significantly greater than that determined by HW (19.4 +/- 6.4%) and SF (18.8 +/- 5.5%). Results from the lean subset also revealed that %BF determined by ADP (17.1 +/- 3.7%) was significantly higher than %BF estimates by HW (14.3 +/- 2.8%) and SF (15.2 +/- 3.2%). The regression equation for the entire sample (%BF HW = 0.937%BF ADP - 0.452, r(2) = 0.73, standard error of estimates (SEE) = 3.34) did not differ from the line of identity. In contrast, the line of identity differed significantly from the regression equation for the lean subset of female athletes (%BF HW = 0.48%BF ADP + 6.115, r(2) = 0.41, SEE = 2.18). The results of this investigation indicate that ADP significantly overestimated %BF by 8% in female athletes and by 16% for a leaner subset of the sample compared with HW. It appears that %BF estimates by SF may be more accurate than those obtained by ADP for female college athletes, regardless of body composition. Coaches and trainers evaluating body composition should consider the use of SF before ADP when measuring %BF in female college athletes. Sports scientists should continue to examine the possible gender and body composition bias for ADP.

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