Body composition is defined as the relative amounts of the various chemical components of the body,1 and various methods have been described to provide a quantitative estimate of it. Such methods differ in their applicability to research, referral veterinary practice, and first-opinion practice. Some investigators regard chemical analysis as the most appropriate method for body composition analysis,2 but this method is laborious and not applicable to clinical practice. Other techniques with reasonable precision and accuracy include total body water measurement and DEXA.1
Dual-energy x-ray absorptiometry estimates body composition by use of photons of 2 energy levels (70 and 140 kVp), which are impeded differently by bone mineral, lipid, and lean tissue. Algorithms are then used to calculate the quantity and type of tissue in each pixel scanned. Similar to other body composition techniques, DEXA relies on the assumption that lean body mass is uniformly hydrated at 0.73 mL of water/g.3 Previous studies3,4 have validated DEXA for body composition analysis in dogs; results are generally precise, and accuracy is acceptable, although some limitations remain.3 The technique has also been used as a noninvasive reference method, when validating other (eg, morphometric) methods of composition analysis.2,5,6 However, although DEXA is available at some referral institutions, such methods are still not feasible for use in general practice. Instead, simpler techniques are required and include body condition scoring and electrical conductance methods.
In companion animals, the most widely accepted and practical method of assessing body composition is body condition scoring.5–7 All body condition scoring systems assess visual and palpable characteristics, such as subcutaneous fat, abdominal fat, and superficial musculature. These assessments are quick and easy to perform, and when used by trained individuals, scores correlate well with body fat mass determined via DEXA and are repeatable among observers.2,6 Even when assessed by inexperienced individuals, BCS correlates well with results of DEXA.6 These systems are a valuable means of assessing body composition in epidemiological studies.8–10
Bioelectrical impedance analysis is a safe, noninvasive, rapid, and portable method to estimate body composition in healthy dogs, cats, and humans.11–13 This technique assesses body composition by measuring the nature of the conductance of an applied electrical current in the body.14 Body fluids and electrolytes are responsible for conductance, and because adipose tissue is less hydrated than lean body tissues, a greater proportion of adipose tissue results in lower conducting volume and hence larger impedance to current passage. A new handheld bioimpedance monitor has recently been validated for dogs, and the manufacturers report good correlation (R2 = 0.75) with percentage body fat measured by use of the deuterium oxide dilution method.15 Nonetheless, before this method can be widely recommended, there is a need for independent validation. Therefore, on the basis of the hypothesis that bioimpedance provides a useful tool for measuring adiposity in dogs, the purpose of the present study was to assess performance of a bioimpedance monitor, compared with DEXA as a reference method, in dogs, prior to weight loss and after a weight-loss regimen.
Body condition score
Coefficient of variation
Dual-energy x-ray absorptiometry
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