Diagnostic performance of body mass index to identify obesity as defined by body adiposity: a systematic review and meta-analysis
ABSTRACT We performed a systematic review and meta-analysis of studies that assessed the performance of body mass index (BMI) to detect body adiposity.
Data sources were MEDLINE, EMBASE, Cochrane, Database of Systematic Reviews, Cochrane CENTRAL, Web of Science, and SCOPUS. To be included, studies must have assessed the performance of BMI to measure body adiposity, provided standard values of diagnostic performance, and used a body composition technique as the reference standard for body fat percent (BF%) measurement. We obtained pooled summary statistics for sensitivity, specificity, positive and negative likelihood ratios (LRs), and diagnostic odds ratio (DOR). The inconsistency statistic (I2) assessed potential heterogeneity.
The search strategy yielded 3341 potentially relevant abstracts, and 25 articles met our predefined inclusion criteria. These studies evaluated 32 different samples totaling 31 968 patients. Commonly used BMI cutoffs to diagnose obesity showed a pooled sensitivity to detect high adiposity of 0.50 (95% confidence interval (CI): 0.43-0.57) and a pooled specificity of 0.90 (CI: 0.86-0.94). Positive LR was 5.88 (CI: 4.24-8.15), I (2)=97.8%; the negative LR was 0.43 (CI: 0.37-0.50), I (2)=98.5%; and the DOR was 17.91 (CI: 12.56-25.53), I (2)=91.7%. Analysis of studies that used BMI cutoffs >or=30 had a pooled sensitivity of 0.42 (CI: 0.31-0.43) and a pooled specificity of 0.97 (CI: 0.96-0.97). Cutoff values and regional origin of the studies can only partially explain the heterogeneity seen in pooled DOR estimates.
Commonly used BMI cutoff values to diagnose obesity have high specificity, but low sensitivity to identify adiposity, as they fail to identify half of the people with excess BF%.
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ABSTRACT: Rural women have high prevalence of obesity and prehypertension. Obesity, if associated with poor physical function, may have implications for applying activity guidelines for women volunteering for lifestyle modification. This study examined associations of body mass index (BMI) and percent body fat with measures of 1-mile walk time, post-walk perceived exertion, and 10-repetition chair stands in rural women ages 40-69. Cross-sectional baseline data were collected using standardized methods from 289 rural women with prehypertension who volunteered for a lifestyle clinical trial for reducing blood pressure. ANOVAs and linear regression were used for analysis. With exception of the chair stands measure across categories of BMI, group differences were noted in all measures across categories of BMI and percent body fat, with women in the two highest categories demonstrating the poorest performance. These two body composition measures were significant predictors for 1-mile walk-time and 10-repetition chair stands, after controlling for confounding variables. Poorer scores were observed in performance-based measures in women with higher BMI and percent body fat, though mean scores were above thresholds for functional limitation. Physical performance needs to be assessed and addressed by physical therapists when providing lifestyle interventions for overweight and obese women.
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ABSTRACT: Body mass index (BMI) (kg/m(2)) is used internationally to assess body mass or adiposity. However, BMI does not discriminate body fat content or distribution and may vary among ethnicities. Many women with normal BMI are considered healthy, but may have an unidentified "hidden fat" profile associated with higher metabolic disease risk. If only BMI is used to indicate healthy body size, it may fail to predict underlying risks of diseases of lifestyle among population subgroups with normal BMI and different adiposity levels or distributions. Higher body fat levels are often attributed to excessive dietary intake and/or inadequate physical activity. These environmental influences regulate genes and proteins that alter energy expenditure/storage. Micro ribonucleic acid (miRNAs) can influence these genes and proteins, are sensitive to diet and exercise and may influence the varied metabolic responses observed between individuals. The study aims are to investigate associations between different body fat profiles and metabolic disease risk; dietary and physical activity patterns as predictors of body fat profiles; and whether these risk factors are associated with the expression of microRNAs related to energy expenditure or fat storage in young New Zealand women. Given the rising prevalence of obesity globally, this research will address a unique gap of knowledge in obesity research. A cross-sectional design to investigate 675 NZ European, Māori, and Pacific women aged 16-45 years. Women are classified into three main body fat profiles (n = 225 per ethnicity; n = 75 per body fat profile): 1) normal BMI, normal body fat percentage (BF%); 2) normal BMI, high BF%; 3) high BMI, high BF%. Regional body composition, biomarkers of metabolic disease risk (i.e. fasting insulin, glucose, HbA1c, lipids), inflammation (i.e. IL-6, TNF-alpha, hs-CRP), associations between lifestyle factors (i.e. dietary intake, physical activity, taste perceptions) and microRNA expression will be investigated. This research targets post-menarcheal, premenopausal women, potentially exhibiting lifestyle behaviours resulting in excess body fat affecting metabolic health. These behaviours may be characterised by specific patterns of microRNA expression that will be explored in terms of tailored solutions specific to body fat profile groups and ethnicities. ACTRN12613000714785.SpringerPlus 12/2015; 4(1):128. DOI:10.1186/s40064-015-0916-8
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ABSTRACT: Hypovitaminosis D has been frequently reported after renal transplantation, but the impact of obesity and other factors in the reduction of vitamin D levels is not well established. We aimed to evaluate risk factors contributing to hypovitaminosis D among nondiabetic renal transplant recipients (RTR) with serum creatinine <2.0 mg/dL, at least 6 months after transplantation. One hundred RTR were subjected to anthropometric evaluation and body composition assessment through bioelectrical impedance analysis; blood samples were drawn for biochemical and hormonal determinations and clinical data were retrieved from the medical records. Hypovitaminosis D was observed in 65% and overweight (body mass index, BMI >25 kg/m(2)) in 59% of cases with a significant median weight gain after transplantation of 5.1 kg. An inadequate distribution of body fat was evidenced in 50% of males and in 58% of females. Patients with either vitamin D deficiency or insufficiency presented significantly higher median values of body fat and weight gain since transplantation, as well as lower lean mass compared with patients with normal vitamin D levels (P < 0.001). Moreover, median values of waist circumference, BMI, serum leptin and parathyroid hormone levels were significantly higher in the group with vitamin D deficiency. A multivariate linear regression analysis then revealed that body fat and leptin levels, but not skin color, gender, age, glucocorticoid use, renal function, microalbuminuria and other confounding factors, were independently associated with low levels of 25 hydroxyvitamin D3 even after adjustments for seasonal variations. In conclusion, the present study showed body fat and serum leptin levels to be the only independent risk factors for hypovitaminosis D among RTR.02/2015; 8(1):49-53. DOI:10.1093/ckj/sfu120