Body mass index and measures of body fat for defining obesity and underweight: a cross-sectional, population-based study

Abstract

BackgroundThe body mass index (BMI) is commonly used as a surrogate marker for adiposity. However, the BMI indicates weight-for-height without considering differences in body composition and the contribution of body fat to overall body weight.The aim of this cross-sectional study was to identify sex-and-age-specific values for percentage body fat (%BF), measured using whole body dual energy x-ray absorptiometry (DXA), that correspond to BMI 18.5 kg/m2 (threshold for underweight), 25.0 kg/m2 (overweight) and 30.0 kg/m2 (obesity) and compare the prevalence of underweight, overweight and obesity in the adult white Australian population using these BMI thresholds and equivalent values for %BF. These analyses utilise data from randomly-selected men (n = 1446) and women (n = 1045), age 20–96 years, who had concurrent anthropometry and DXA assessments as part of the Geelong Osteoporosis Study, 2001–2008.ResultsValues for %BF cut-points for underweight, overweight and obesity were predicted from sex, age and BMI. Using these cut-points, the age-standardised prevalence among men for underweight was 3.1% (95% CI 2.1, 4.1), overweight 40.4% (95% CI 37.7, 43.1) and obesity 24.7% (95% CI 22.2, 27.1); among women, prevalence for underweight was 3.8% (95% CI 2.6, 5.0), overweight 32.3% (95% CI 29.5, 35.2) and obesity 29.5% (95% CI 26.7, 32.3). Prevalence estimates using BMI criteria for men were: underweight 0.6% (95% CI 0.2, 1.1), overweight 45.5% (95% CI 42.7, 48.2) and obesity 19.7% (95% CI 17.5, 21.9); and for women, underweight 1.4% (95% CI 0.7, 2.0), overweight 30.3% (95% CI 27.5, 33.1) and obesity 28.2% (95% CI 25.4, 31.0).ConclusionsUtilising a single BMI threshold may underestimate the true extent of obesity in the white population, particularly among men. Similarly, the BMI underestimates the prevalence of underweight, suggesting that this body build is apparent in the population, albeit at a low prevalence. Optimal thresholds for defining underweight and obesity will ultimately depend on risk assessment for impaired health and early mortality.

Characteristics of Female Nonagenarian Participants in an Observational Health Study

“…The mean values for BMI were lower than previously reported values for women aged 70-79 years (27.9 kg/m 2 ) and 80+ years (26.4 kg/m 2 ); similarly, mean %BF was lower than for ages 70-79 years (40.9%) and 80+ years (38.4%) [11]. Only two had low lean mass reflecting agerelated muscle loss and none had sarcopenic obesity.…”

Effects of protein supplementation combined with resistance exercise on body composition and physical function in older adults: a systematic review and meta-analysis

“…The results of the present study may have been subjected to meta-analysis bias. However, previous analyses of treatment effects on body composition changes have suggested that BF% is more suitable for identifying obesity than BMI, which only indicates changes in total body mass (61). We therefore used a group mean BF% of .27% for men and 38% for women to assume that more obese older adults were enrolled in the included trials than overweight or normal-weight older adults (62).…”

Increases in Body Mass Index Following Initiation of Methadone Treatment

“…Second, presentation of the data in pounds permits comparison of our findings with prior studies which solely reported their methadone-associated weight gains in terms of pounds (e.g., Mysels et al, 2011). Finally, the use of BMI as a marker for adiposity may have limitations, especially in adult overweight (BMI 25</=30) males (Pasco et al, 2014; Romero-Corral et al, 2008). Thus, clinically significant weight gain (>/= 5% total body weight per Food and Drug Association) may provide a more sensitive estimate of weight changes during treatment.…”