Measurement challenges and other practical concerns when studying massively obese individuals.
ABSTRACT To describe the measurement challenges faced and to evaluate the measurement quality obtained with massively obese individuals.
A cross-sectional analysis of 107 individuals with body mass indices (kg/m2) > or = 50 was conducted. Individuals had their body fat measured via bioimpedance analysis (BIA), their serum leptin levels measured via radioimmunoassay (RIA), and height and weight measured via both laboratory scales and self-report.
Serum leptin appeared to be measured accurately, provided the serum was diluted prior to conducting the RIA. Difficulties remained, however, in evaluating what was an unusual or expected value of leptin among individuals this large. Measures of impedance appeared to provide reasonable ordinal indications of body fatness. However, currently available equations for converting measures of impedance to estimates of percent body fat were highly inaccurate. Self-reported height and weight were reasonably good proxies of measured height and weight among individuals who reported their height and weight. However, a substantial proportion were unable to provide estimates.
The above results suggest there are substantial challenges when trying to obtain meaningful measurements regarding obesity-related variables among massively obese individuals. Other logistic challenges also are discussed. It is hoped future research is directed at overcoming some of these challenges.
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ABSTRACT: The prevalence of obesity and severe obesity continues to increase in the developed world. Apart from obesity's strong association with a variety of health conditions, severely obese individuals (i.e. > or = 300 lb [136 kg]) sometimes have difficulty with ambulation, and often cannot use regular sized clothes, furniture, and assistive devices such as walkers and wheelchairs. The purpose of this study was to assess the relationship between linear body measurements (anthropometry) and weight in severely obese people in order to generate equations to predict such measurements from weight alone. Various body size measurements were obtained from three independent data sets (74 severely obese individuals evaluated at the New York Obesity Research Center, 103 severely obese individuals who participated in the National Center for Health Statistics' National Health and Nutrition Examination Survey III, and a further 90 severely obese individuals evaluated at the New York Obesity Research Center). Linear regression analyses revealed that for each increase of 10 kg (22.04 lb) above 136 kg (300 lb), body diameter measurements increase by 0.9-1.1 cm. These analyses provide body size-to-weight estimates that may help manufacturers develop products and services that are more appropriate for increasing numbers of severely obese individuals.Ergonomics 01/2002; 45(1):49-60. DOI:10.1080/00140130110112627 · 1.61 Impact Factor
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ABSTRACT: In order to maintain body weight regulation, leptin directly or indirectly signals nutritional changes to key organs, but little is known about its target genes in human adipose tissue. Leptin receptor loss of function is a unique way to explore the role of leptin in the regulation of adipose tissue. We studied the consequences of the absence of leptin signaling on adipocyte gene expression in two girls with a mutation in the leptin receptor. The expression levels of the ob gene and adipocyte transcription factors (SREBP1c, C/EPBalpha, beta, PPARgamma1, gamma2) were quantified by RT-PCR in subcutaneous adipose tissue of these patients and of 10 morbidly obese women. Ob mRNA levels in subjects lacking the leptin receptor were not overexpressed but were in the range that could be expected from their BMI (58 and 26 amol/ micro g total mRNA, range in obese women: 26-69). Expression of the five transcription factors was also in the same range in the affected patients and in morbidly obese women (7.7 and 6.8 amol/ micro g total mRNA, range: 2.2-9.4 for SREBP1c, 159 and 51 range: 51-406 for C/EPBalpha, 6.1 and 3.3 range: 2.4-24.8 for C/EPBbeta, 16.7 and 27.4 range: 9.4-29.7 for PPARgamma1 and 1.7 and 5.4 amol/ micro g total mRNA range: 1.7-8.8 for PPARgamma2). Significant correlation was found between the mRNA levels of leptin and PPARgamma2 and leptin and C/EBPalpha whereas no correlation was observed between leptin and SREBP1c, PPARgamma1, or C/EBPbeta mRNA levels. In patients lacking leptin signaling, the fact that ob gene expression is adequately adapted to their body fat mass argues against a direct negative feedback loop in the regulation of leptin expression in humans. The normal expression of several transcription factors, known to be dependent of the nutritional status, suggests that leptin is not a major contributor of their in vivo transcriptional regulation in human adipose tissue.International Journal of Obesity 01/2003; 26(12):1533-8. DOI:10.1038/sj.ijo.0802180 · 5.39 Impact Factor
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ABSTRACT: Severe obesity is accompanied by large increases in fat mass and alterations in the composition of fat free mass, in particular total body water and its extracellular compartment. The physical size limitations imposed by severe obesity, and variations in body composition from that of normal weight, pose tremendous challenges to the measurement of body composition. This review focuses on some of the methodological and practical issues associated with the use of common body composition methods, and identifies available published information on feasible methods for use in the severely obese. There is little published research regarding what body composition methods can be used with confidence in the severely obese populations. A simple three-compartment model combining measurements of body density by air displacement plethysmography and total body water by bio-electrical impedance can provide measurements of percentage body fat in the severely obese that are comparable with a traditional, highly technical three-compartment model requiring facilities such as isotope ratio mass spectrometry along with a substantial technical expertise. This review highlights some of the basic challenges faced by researchers and clinicians when conducting body composition assessments in severely obese patients. A simple three-compartment model that is accurate and easy to perform appears to be promising for use in this population. Further research is needed, however, on this and other feasible methods of body composition assessment in a diverse group of severely obese people.Current Opinion in Clinical Nutrition and Metabolic Care 12/2005; 8(6):602-6. DOI:10.1097/01.mco.0000171122.60665.5f · 3.97 Impact Factor