Comparison of the Classification of Obesity by BMI vs. Dual‐energy X‐ray Absorptiometry in the Newfoundland Population

Although BMI is the most widely used measure of obesity, debate still exists on how accurately BMI defines obesity. In this study, adiposity status defined by BMI and dual‐energy X‐ray absorptiometry (DXA) was compared in a large population to evaluate the accuracy of BMI. A total of 1,691 adult volunteers from Newfoundland and Labrador participated in the study. BMI and body fat percentage (%BF) were measured for all subjects following a 12‐h fasting period. Subjects were categorized as underweight (UW), normal weight (NW), overweight (OW), or obese (OB) based on BMI and %BF criteria. Differences between the two methods were compared within gender and by age‐groups. According to BMI criteria, 1.2% of women were classified as UW, 44.2% as NW, 34.2% as OW, and 20.3% as OB. When women were classified according to %BF criteria, 2.2% were UW, 29.6% were NW, 30.9% were OW, and 37.1% were OB. The overall discrepancy between the two methods for women was substantial at 34.7% (14.6% for NW and 16.8% for OB, P < 0.001). In men, the overall discrepancy was 35.2% between BMI and DXA (17.6% for OW and 13.5% for OB, P < 0.001). Misclassification by BMI was dependent on age, gender, and adiposity status. In conclusion, BMI misclassified adiposity status in approximately one‐third of women and men compared with DXA. Caution should be taken when BMI is used in clinical and scientific research as well as clinical practice.     

Concordance of BAI and BMI with DXA in the Newfoundland Population

Background:

Body adiposity index (BAI), indirect method proposed to predict adiposity, was developed using Mexican Americans and very little data are available regarding its validation in Caucasian populations to date.

Objective:

The study objectives were to validate the BAI with dual‐energy X‐ray absorptiometry (DXA) body fat percentage (%BF), taking into consideration the gender and adiposity status.

Design and Methods:

A total of 2,601 subjects (Male 662, Female 1939) from our Complex Diseases in the Newfoundland population: Environment and Genetics (CODING) study participated in this investigation. Pearson correlations, with the entire cohort along with men and women separately, were used to compare the correlation of both BAI and BMI with %BF. Additionally, the concordance between BAI and BMI with %BF were also performed among normal‐weight (NW), overweight (OW), and obese (OB) groups. Adiposity status was determined by the Bray Criteria according to DXA %BF.

Results:

BAI performs better than BMI in our Caucasian population by: (1) reflecting the gender difference in total %BF between women and men, (2) correlating better with DXA %BF than BMI when women and men are combined, and (3) performing better in NW and OW subjects for both the sexes. However, BAI performs less effectively than BMI in OB men and women.

Conclusion:

In summary, the BAI method is a better estimate of adiposity than BMI in non‐OB subjects in our Caucasian population. A measurement sensitive to the changes in adiposity for both men and women is suggested to be incorporated into the present BAI equation to increase accuracy.     

Effects of breastfeeding on trajectories of body fat and BMI throughout childhood

Objective: To investigate the effect of breastfeeding in healthy boys and girls on their trajectories of percent body fat (%BF) and BMI standard deviation scores (BMI–SDS) throughout childhood. Methods and Procedures: Analyses of the DOrtmund Nutritional and Anthropometric Longitudinally Designed (DONALD) Study included data from 219 male and 215 female term participants, born between 1984 and 1999, with repeated anthropometric measurements between 0.5 and 7 years and prospective data on duration of breastfeeding. Results: Among boys with an overweight mother (OW‐M), analyses adjusted for potential confounders revealed that not or shortly breastfed (≤17 weeks) boys did not experience the age‐dependent decrease in %BF seen in all children with normal weight mothers (NW‐Ms). In contrast, boys fully breastfed for >17 weeks were protected against the adverse effect of maternal overweight (effect of long breastfeeding vs. no/short breastfeeding among boys with OW‐Ms: 0.46%/year; s.e. 0.18; P = 0.01). There was also a suggestion of an interaction between maternal overweight and breastfeeding for the BMI–SDS trajectory (0.08 SDS/year; s.e. 0.04; P = 0.07). Among boys with NW‐Ms mothers and the corresponding subgroups of girls, breastfeeding had little effect on the development of %BF or BMI–SDS throughout childhood. Discussion: Our study suggests that breastfeeding could offset a potential programming effect for childhood adiposity among boys with OW‐Ms, to whom advice to breast‐feed should thus be specifically targeted.     

Body composition determinants of metabolic phenotypes of obesity in nonobese and obese postmenopausal women

Objective : Although obesity is typically associated with increased cardiovascular risk, a subset of obese individuals display a normal metabolic profile (“metabolically healthy obese,” MHO) and conversely, a subset of nonobese subjects present with obesity‐associated cardiometabolic abnormalities (“metabolically obese nonobese,” MONO). The aim of this cross‐sectional study was to identify the most important body composition determinants of metabolic phenotypes of obesity in nonobese and obese healthy postmenopausal women. Design and Methods : We studied a total of 150 postmenopausal women (age 54 ± 7 years, mean ± 1 SD). Based on a cardiometabolic risk score, nonobese (body mass index [BMI] ≤ 27) and obese women (BMI > 27) were classified into “metabolically healthy” and “unhealthy” phenotypes. Total and regional body composition was assessed with dual‐energy X‐ray absorptiometry (DXA). Results : In both obese and nonobese groups, the “unhealthy” phenotypes were characterized by frequent bodyweight fluctuations, higher biochemical markers of insulin resistance, hepatic steatosis and inflammation, and higher anthropometric and DXA‐derived indices of central adiposity, compared with “healthy” phenotypes. Indices of total adiposity, peripheral fat distribution and lean body mass were not significantly different between “healthy” and “unhealthy” phenotypes. Despite having increased fat mass, MHO women exhibited comparable cardiometabolic parameters with healthy nonobese, and better glucose and lipid levels than MONO. Two DXA‐derived indices, trunk‐to‐legs and abdominal‐to‐gluteofemoral fat ratio were the major independent determinants of the “unhealthy” phenotypes in our cohort. Conclusions : The “metabolically obese phenotype” is associated with bodyweight variability, multiple cardiometabolic abnormalities and an excess of central relative to peripheral fat in postmenopausal women. DXA‐derived centrality ratios can discriminate effectively between metabolic subtypes of obesity in menopause.     

Assessing Body Composition among 3‐ to 8‐Year‐Old Children: Anthropometry,BIA, and DXA

Objective: To examine the inter‐relationships of body composition variables derived from simple anthropometry [BMI and skinfolds (SFs)], bioelectrical impedance analysis (BIA), and dual energy x‐ray (DXA) in young children. Research Methods and Procedures: Seventy‐five children (41 girls, 34 boys) 3 to 8 years of age were assessed for body composition by the following methods: BMI, SF thickness, BIA, and DXA. DXA served as the criterion measure. Predicted percentage body fat (%BF), fat‐free mass (FFM; kilograms), and fat mass (FM; kilograms) were derived from SF equations [Slaughter (SL)1 and SL2, Deurenberg (D) and Dezenberg] and BIA. Indices of truncal fatness were also determined from anthropometry. Results: Repeated measures ANOVA showed significant differences among the methods for %BF, FFM, and FM. All methods, except the D equation (p = 0.08), significantly underestimated measured %BF (p < 0.05). In general, correlations between the BMI and estimated %BF were moderate (r = 0.61 to 0.75). Estimated %BF from the SL2 also showed a high correlation with DXA %BF (r = 0.82). In contrast, estimated %BF derived from SFs showed a low correlation with estimated %BF derived from BIA (r = 0.38); likewise, the correlation between DXA %BF and BIA %BF was low (r = 0.30). Correlations among indicators of truncal fatness ranged from 0.43 to 0.98. Discussion: The results suggest that BIA has limited utility in estimating body composition, whereas BMI and SFs seem to be more useful in estimating body composition during the adiposity rebound. However, all methods significantly underestimated body fatness as determined by DXA, and, overall, the various methods and prediction equations are not interchangeable.     

High Dietary Magnesium Intake Is Associated with Low Insulin Resistance in the Newfoundland Population

Background

Magnesium plays a role in glucose and insulin homeostasis and evidence suggests that magnesium intake is associated with insulin resistance (IR). However, data is inconsistent and most studies have not adequately controlled for critical confounding factors.

Objective

The study investigated the association between magnesium intake and IR in normal-weight (NW), overweight (OW) and obese (OB) along with pre- and post- menopausal women.

Design

A total of 2295 subjects (590 men and 1705 women) were recruited from the CODING study. Dietary magnesium intake was computed from the Willett Food Frequency Questionnaire (FFQ). Adiposity (NW, OW and OB) was classified by body fat percentage (%BF) measured by Dual-energy X-ray absorptiometry according to the Bray criteria. Multiple regression analyses were used to test adiposity-specific associations of dietary magnesium intake on insulin resistance adjusting for caloric intake, physical activity, medication use and menopausal status.

Results

Subjects with the highest intakes of dietary magnesium had the lowest levels of circulating insulin, HOMA-IR, and HOMA-ß and subjects with the lowest intake of dietary magnesium had the highest levels of these measures, suggesting a dose effect. Multiple regression analysis revealed a strong inverse association between dietary magnesium with IR. In addition, adiposity and menopausal status were found to be critical factors revealing that the association between dietary magnesium and IR was stronger in OW and OB along with Pre-menopausal women.

Conclusion

The results of this study indicate that higher dietary magnesium intake is strongly associated with the attenuation of insulin resistance and is more beneficial for overweight and obese individuals in the general population and pre-menopausal women. Moreover, the inverse correlation between insulin resistance and dietary magnesium intake is stronger when adjusting for %BF than BMI.     

Circulating oxidized LDL and inflammation in extreme pediatric obesity

Oxidative stress and inflammation have not been well-characterized in extreme pediatric obesity. We compared levels of circulating oxidized low-density lipoprotein (oxLDL), C-reactive protein (CRP), and interleukin-6 (IL-6) in extremely obese (EO) children to normal weight (NW) and overweight/obese (OW/OB) children. OxLDL, CRP, IL-6, BMI, blood pressure, and fasting glucose, insulin, and lipids were obtained in 225 children and adolescents (age 13.5 ± 2.5 years; boys 55%). Participants were classified into three groups based on gender- and age-specific BMI percentile: NW (<85th, n = 127), OW/OB (85th- <1.2 times the 95th percentile, n = 64) and EO (≥1.2 times the 95th percentile or BMI ≥35 kg/m(2), n = 34). Measures were compared across groups using analysis of covariance, adjusted for gender, age, and race. Blood pressure, insulin, and lipids worsened across BMI groups (all P < 0.0001). OxLDL (NW: 40.8 ± 9.0 U/l, OW/OB: 45.7 ± 12.1 U/l, EO: 63.5 ± 13.8 U/l) and CRP (NW: 0.5 ± 1.0 mg/l, OW/OB: 1.4 ± 2.9 mg/l, EO: 5.6 ± 4.9 mg/l) increased significantly across BMI groups (all groups differed with P < 0.01). IL-6 was significantly higher in EO (2.0 ± 0.9 pg/ml) compared to OW/OB (1.3 ± 1.2 pg/ml, P < 0.001) and NW (1.1 ± 1.0 pg/ml, P < 0.0001) but was not different between NW and OW/OB. Extreme pediatric obesity, compared to milder forms of adiposity and NW, is associated with higher levels of oxidative stress and inflammation, suggesting that markers of early cardiovascular disease and type 2 diabetes mellitus are already present in this young population.     

Severely Obese Have Greater LPS‐stimulated TNF‐α Production Than Normal Weight African‐American Women

Obesity is associated with an increase in chronic, low‐grade inflammation which has been implicated in the development of type 2 diabetes mellitus and cardiovascular disease. The purpose of this study was to determine whether obesity was associated with an elevation of whole blood lipopolysaccharide (LPS)‐stimulated tumor necrosis factor‐α (TNF‐α) production. African‐American women were recruited from a larger study and assigned to one of five groups based on BMI: normal weight (NORM; BMI 20–25, n = 7), overweight (OVER; BMI 25–30, n = 12), class 1 obese (OB1; BMI 30–35, n = 19), class 2 obese (OB2; BMI 35–40, n = 10), or class 3 obese (OB3; BMI >40, n = 17). Body composition was determined via a whole body dual‐energy X‐ray absorptiometry (DXA) scan. Venous blood samples were collected following an overnight fast (>8 h), and stimulated with five doses of LPS (Salmonella enteriditis): 80, 40, 20, 10, and 5 µg/ml for 24 h in a 37 °C, 5% CO₂ incubator. Following stimulation, TNF‐α was measured using enzyme‐linked immunosorbent assay. OB3 produced 365% more TNF‐α than NORM at an LPS dose of 20 µg/ml (P < 0.05). When maximal TNF‐α production was assessed regardless of LPS dose, OB3 produced 230% more than NORM and OVER produced 190% more than NW (P = 0.001). Total and trunk fat mass and BMI were significantly correlated with maximal TNF‐α production and LPS = 20 µg/ml. Our findings are consistent with previous reports suggesting a relationship between increased adiposity and inflammatory marker production. This is one of the first studies to focus on African‐American women, who have higher rates of obesity.     

Reformulation of BMI and Percent Body Fat to Remove the Height Bias in 8‐year‐olds

BMI and percent body fat (%BF) are both related to height (Ht) in prepubertal children, so may misrepresent childhood adiposity, especially in tall or short children. We sought to construct replacement functions for BMI and %BF that are independent of Ht. Fat mass (FM) was measured using dual‐energy X‐ray absorptiometry, together with Ht and body mass (BM) in 746 healthy boys and girls aged 8 years (0.34 s.d.). Relationships between BM, FM, and Ht were measured and values of p and q derived such that the functions BM. Ht^?p and FM.BM^?q were unrelated to Ht. BM was not directly proportional to Ht², BMI being significantly related to Ht in both boys and girls (P < 0.001). BM was proportional to Ht³, BM. Ht^?3 being independent of Ht. Similarly, FM was not directly proportional to BM and %BF was significantly related to Ht (P < 0.001). While FM was proportional to BM², FM.BM^?1.5 was the function found to be independent of Ht. Using the 85th and 95th percentiles as the cutoffs for overweight and obesity respectively, 6.4% of the boys and 6.8% of the girls were classified differently by BMI and the Ht independent measure BM. Ht^?3. Similarly, 10.1% boys and 13.7% girls were classified differently by %BF and the Ht independent measure FM.BM^?1.5. We propose that improved diagnostic accuracy of body composition in 8‐year‐olds is provided by the BM function (BMF, BM. Ht^?3) and FM function (FMF, FM.BM^?1.5) replacing BMI and %BF, which both overestimate the adiposity of taller children and underestimate it in shorter children.     

Accelerated Growth in Early Life and Obesity in Preschool Chilean Children

In Chile, childhood obesity rates are high. The purpose of this article is to compare BMI growth characteristics of normal (N), overweight (OW), and obese (OB) 5‐year olds from 0 to 5 years and explore the influence of some prenatal factors on these patterns of growth. The study was done on a retrospective cohort of 1,089 5‐year olds with birth weight >2,500 g. Weight and height were obtained from records at nine occasions (0–36 months); at 52 and 60 months, we measured them. At 60 months, children were classified as N, OW, and OB. At each age, BMI and z‐score of BMI (BMI Z) differences were compared among groups. The influence of birth weight, pre‐pregnancy BMI, and prenatal variables (weight gain, smoking, and presence of diabetes and preeclampsia) on BMI Z differences between N and OB was also explored. Adiposity rebound (AR) was not observed for the N, although for the OW, it occurred ～52 months and for the OB at ～24 months. BMI Z differences between N and OB were significant from birth, but were greatest between 6–12 and 36–52 months. Additional adjustment by birth weight, pre‐pregnancy BMI, and prenatal variables decreased the BMI Z differences for the first 24 months with virtually no effect after this age. Accelerated growth in OB children from post‐transition countries occurs immediately after birth, much earlier than the AR. The influence of prenatal factors on adiposity acquisition may extend at most until 2 years of life, although BMI gains thereafter are more related to postnatal variables.     

Relationship of visceral adiposity to cardiovascular disease risk factors in black and white teens

Objective: We tested the hypothesis that visceral adiposity, compared with general adiposity, would explain more of the variance in cardiovascular disease (CVD) risk factors. Research Method and Procedures: Subjects were 464 adolescents (238 black and 205 girls). Adiposity measures included visceral adipose tissue (VAT; magnetic resonance imaging), percent body fat (%BF; DXA), BMI, and waist girth (anthropometry). CVD risk factors were fasting insulin, fibrinogen, total to high‐density lipoprotein‐cholesterol ratio, triglycerides (TGs), systolic blood pressure, and left ventricular mass indexed to height^2.7. Results: After adjustment for age, race, and sex, all adiposity indices explained significant proportions of the variance in all of the CVD risk factors; %BF tended to explain more variance than VAT. Regression models that included both %BF and VAT found that both indices explained independent proportions of the variance only for total to high‐density lipoprotein‐cholesterol ratio. For TGs, the model that included both %BF and VAT found that only VAT was significant. For systolic blood pressure and left ventricular mass indexed to height^2.7, anthropometric measures explained more of the variance than VAT and %BF. Discussion: The hypothesis that visceral adiposity would explain more variance in CVD risk than general adiposity was not supported in this relatively large sample of black and white adolescents. Only for TGs did it seem that VAT was more influential than %BF. Perhaps the deleterious effect of visceral adiposity becomes greater later in life as it increases in proportion to general adiposity.     

Short-Term Overfeeding Increases Circulating Adiponectin Independent of Obesity Status

Background

Adiponectin is an adipose tissue derived hormone which strengthens insulin sensitivity. However, there is little data available regarding the influence of a positive energy challenge (PEC) on circulating adiponectin and the role of obesity status on this response.

Objective

The purpose of this study was to investigate how circulating adiponectin will respond to a short-term PEC and whether or not this response will differ among normal-weight(NW), overweight(OW) and obese(OB).

Design

We examined adiponectin among 64 young men (19-29 yr) before and after a 7-day overfeeding (70% above normal energy requirements). The relationship between adiponectin and obesity related phenotypes including; weight, percent body fat (%BF), percent trunk fat (%TF), percent android fat (%AF), body mass index (BMI), total cholesterol, HDLc, LDLc, glucose, insulin, homeostatic model assessment insulin resistance (HOMA-IR) and β-cell function (HOMA-β) were analyzed before and after overfeeding.

Results

Analysis of variance (ANOVA) and partial correlations were used to compute the effect of overfeeding on adiponectin and its association with adiposity measurements, respectively. Circulating Adiponectin levels significantly increased after the 7-day overfeeding in all three adiposity groups. Moreover, adiponectin at baseline was not significantly different among NW, OW and OB subjects defined by either %BF or BMI. Baseline adiponectin was negatively correlated with weight and BMI for the entire cohort and %TF, glucose, insulin and HOMA-IR in OB. However, after controlling for insulin resistance the correlation of adiponectin with weight, BMI and %TF were nullified.

Conclusion

Our study provides evidence that the protective response of adiponectin is preserved during a PEC regardless of adiposity. Baseline adiponectin level is not directly associated with obesity status and weight gain in response to short-term overfeeding. However, the significant increase of adiponectin in response to overfeeding indicates the physiological potential for adiponectin to attenuate insulin resistance during the development of obesity.     

Expression of the Bitter Taste Receptor,T2R38, in Enteroendocrine Cells of the Colonic Mucosa of Overweight/Obese vs. Lean Subjects

Bitter taste receptors (T2Rs) are expressed in the mammalian gastrointestinal mucosa. In the mouse colon, T2R138 is localized to enteroendocrine cells and is upregulated by long-term high fat diet that induces obesity. The aims of this study were to test whether T2R38 expression is altered in overweight/obese (OW/OB) compared to normal weight (NW) subjects and characterize the cell types expressing T2R38, the human counterpart of mouse T2R138, in human colon. Colonic mucosal biopsies were obtained during colonoscopy from 35 healthy subjects (20 OW/OB and 15 NW) and processed for quantitative RT-PCR and immunohistochemistry using antibodies to T2R38, chromogranin A (CgA), glucagon like peptide-1 (GLP-1), cholecystokinin (CCK), or peptide YY (PYY). T2R38 mRNA levels in the colonic mucosa of OW/OB were increased (> 2 fold) compared to NW subjects but did not reach statistical significance (P = 0.06). However, the number of T2R38 immunoreactive (IR) cells was significantly increased in OW/OB vs. NW subjects (P = 0.01) and was significantly correlated with BMI values (r = 0.7557; P = 0.001). In both OW/OB and NW individuals, all T2R38-IR cells contained CgA-IR supporting they are enteroendocrine. In both groups, T2R38-IR colocalized with CCK-, GLP1- or PYY-IR. The overall CgA-IR cell population was comparable in OW/OB and NW individuals. This study shows that T2R38 is expressed in distinct populations of enteroendocrine cells in the human colonic mucosa and supports T2R38 upregulation in OW/OB subjects. T2R38 might mediate host functional responses to increased energy balance and intraluminal changes occurring in obesity, which could involve peptide release from enteroendocrine cells.     

Metabolic syndrome in healthy obese,overweight, and normal weight individuals: The atherosclerosis risk in communities study

Objective:

There is recent interest in characterizing the subset of obese (OB) individuals who have healthy metabolic profiles yet only two studies have examined this group prospectively but not in racially diverse populations.

Design and Methods:

We analyzed factors associated with the prevalence and incidence of metabolic syndrome (MetSyn) among individuals grouped by BMI categories in a multi‐center, community‐based cohort of 14,663 African‐American and white men and women aged 45‐64 years at recruitment in 1987‐1989, the Atherosclerosis Risk in Communities (ARIC) Study. Logistic and proportional hazards regression were utilized to estimate odds ratios (ORs) for the prevalence and hazard ratios (HRs) for incidence of MetSyn with 95% confidence intervals (CIs).

Results:

At visit 1, MetSyn was positively associated with age, female gender, African‐American race, and inversely related to education, associations being more pronounced among normal weight (NW) subjects. Among those without MetSyn at visit 1, OB subjects were more likely to develop MetSyn compared with NW (HR (95% CI): 4.53 (4.09‐5.01)). Several factors were associated with incident MetSyn among NW, including older age (per year: 1.05 (1.03‐1.06)), female gender (vs. male: 1.29 (1.10‐1.52)), heavy alcohol intake (vs. never: 0.75 (0.59‐0.94)), and physical activity (tertile 3 vs. tertile 1: 0.71 (0.58‐0.86)) but not OB. Weight gain (>5%) was also more highly associated with MetSyn in NW (1.61 (1.28‐2.02)) compared with OB (1.01 (0.85‐1.20)).

Conclusions:

We conclude that lifestyle factors may play a stronger role in the development of MetSyn in NW individuals compared with OB and that metabolically healthy obesity may not be a stable condition.     

Relationships of cardiac autonomic function with metabolic abnormalities in childhood obesity

Objective: The objective was to examine cardiovascular autonomic (cANS) function and its potential relationships with leptin resistance, insulin resistance, oxidative stress, and inflammation in a pediatric sample with varying levels of obesity. Research Methods and Procedures: Participants were normal‐weight (NW; BMI <85th percentile, 6 male, 4 female), overweight (OW; 85th percentile < BMI <95th percentile, 6 male, 4 female), and obese children (OB; BMI >95th percentile, 6 male, 10 female) who had cANS function assessed via heart rate variability (HRV) methods during resting conditions. Standard time‐domain and frequency‐domain measures [high‐frequency normalized units (HFnu; measure of parasympathetic nervous system activity) and low frequency:high‐frequency ratio (LF:HF; overall sympathovagal balance)] of HRV were calculated. Fasting blood samples were drawn for measurement of glucose, insulin, lipids, 8‐isoprostane, leptin, soluble leptin‐receptor (sOB‐R), C‐reactive protein (CRP), interleukin‐6 (IL‐6), and tumor necrosis factor‐α (TNF‐α). Results were reported as mean ± standard error of the mean. Results: OB had significantly elevated LF:HF and decreased HFnu when compared with NW (p < 0.05), but no differences between OW and NW were observed. Measures of HRV were significantly related to leptin, insulin resistance, 8‐isoprostane, and CRP (p < 0.05), but these relationships were not significant after adjustment for fat mass. Discussion: When compared with NW, OB but not OW children are characterized by cANS dysfunction and increased leptin, insulin resistance, oxidative stress, and inflammation (CRP). The relationships between these factors seem to be dependent on quantity of fat mass and/or other factors associated with being obese.     

Ten months of exercise improves general and visceral adiposity, bone, and fitness in black girls

Objective: The goal of this study was to evaluate the impact of a 10‐month after‐school physical activity (PA) program on body composition and cardiovascular (CV) fitness in young black girls. Research Methods and Procedures: Subjects were 8‐ to 12‐year‐olds recruited from elementary schools. Body composition was measured using anthropometrics {waist circumference and BMI, DXA [percentage body fat (%BF)] and bone mineral density (BMD)}, and magnetic resonance imaging [visceral adipose tissue (VAT)]. CV fitness was measured using a graded treadmill test. The intervention consisted of 30 minutes homework/healthy snack time and 80 minutes PA (i.e., 25 minutes skills instruction, 35 minutes aerobic PA, and 20 minutes strengthening/stretching). Analyses were adjusted for age, baseline value of the dependent variable, and sexual maturation (pediatrician observation). Results: Mean attendance was 54%. Compared with the control group, the intervention group had a relative decrease in %BF (p < 0.0001), BMI (p < 0.01), and VAT (p < 0.01) and a relative increase in BMD (p < 0.0001) and CV fitness (p < 0.05). Higher attendance was associated with greater increases in BMD (p < 0.05) and greater decreases in %BF (p < 0.01) and BMI (p < 0.05). Higher heart rate during PA was associated with greater increases in BMD (p < 0.05) and greater decreases in %BF (p < 0.005). Discussion: An after‐school PA program can lead to beneficial changes in body composition and CV fitness in young black girls. It is noteworthy that the control and intervention groups differed in change in VAT but not waist circumference. This suggests that changes in central adiposity can occur in response to PA, even in young children, but that waist circumference may not be a good indicator of central adiposity.     

The Association of Serum Total Peptide YY (PYY) with Obesity and Body Fat Measures in the CODING Study

Background

PYY is an appetite suppressing hormone. Low circulating PYY has been linked to greater BMI. However data is controversial and this association has not been verified in large human populations.

Objective

The purpose of this study was to investigate if fasting serum total PYY is associated with obesity status and/or adiposity at the population level.

Design

A total of 2094 subjects (Male-523, Female-1571) participated in this investigation. Total PYY was measured in fasting serum by enzyme-linked immunosorbent assay. Obesity status (NW-normal-weight, OW-overweight and OB-obese) was determined by the Bray Criteria according to body fat percentage measured by dual-energy x-ray absorptiometry and the WHO criteria according to BMI. One-way ANOVA and multiple regression was used to assess the adiposity-specific association between PYY and the following; weight, BMI, waist-circumference, hip-circumference, waist-hip ratio, percent body fat (%BF), trunk fat (%TF), android fat (%AF) and gynoid fat (%GF).

Results

PYY was not significantly different among NW, OW and OB groups defined by neither %BF nor BMI for both men and women. However among women, fasting PYY was positively associated with adiposity measures. Women with the highest (Top 33%) waist-circumference, %BF and %TF had significantly higher PYY (10.5%, 8.3% and 9.2% respectively) than women with the lowest (Bottom 33%). Age, smoking, medication use and menopause were all positively associated with PYY levels in women but not in men.

Conclusion

To our knowledge this is the largest population based study, with the most comprehensive analysis and measures of confounding factors, to explore the relationship of circulating PYY with obesity. Contrary to initial findings in the literature we discovered that PYY was positively associated with body fat measures (waist-circumference, %BF and %TF) in women. Although the effect size of the positive association of PYY with obesity in women is small, and potentially negligible, it may in fact represent a protective response against significant weight gain.     

Validation of DXA Body Composition Estimates in Obese Men and Women

The aim of this study was to determine the accuracy of dual‐energy X‐ray absorptiometry (DXA)‐derived percentage fat estimates in obese adults by using four‐compartment (4C) values as criterion measures. Differences between methods were also investigated in relation to the influence of fat‐free mass (FFM) hydration and various anthropometric measurements. Six women and eight men (age 22–54 years, BMI 28.7–39.9 kg/m², 4C percent body fat (%BF) 31.3–52.6%) had relative body fat (%BF) determined via DXA and a 4C method that incorporated measures of body density (BD), total body water (TBW), and bone mineral mass (BMM) via underwater weighing, deuterium dilution, and DXA, respectively. Anthropometric measurements were also undertaken: height, waist and gluteal girth, and anterior‐posterior (A‐P) chest depth. Values for both methods were significantly correlated (r² = 0.894) and no significant difference (P = 0.57) was detected between the means (DXA = 41.1%BF, 4C = 41.5%BF). The slope and intercept for the regression line were not significantly different (P > 0.05) from 1 and 0, respectively. Although both methods were significantly correlated, intraindividual differences between the methods were sizable (4C‐DXA, range = ?3.04 to 4.01%BF) and significantly correlated with tissue thickness (chest depth) or most surrogates of tissue thickness (body mass, BMI, waist girth) but not FFM hydration and gluteal girth. DXA provided cross‐sectional %BF data for obese adults without bias. However, individual data are associated with large prediction errors (±4.2%BF). This error appears to be associated with tissue thickness indicating that the DXA device used may not be able to accurately account for beam hardening in obese cohorts.     

Affective Responses to Increasing Levels of Exercise Intensity in Normal‐weight,Overweight, and Obese Middle‐aged Women

At least 60 min of daily physical activity (PA) are recommended for weight control, a target achieved by only 3% of obese (OB) women. The purposes of this study were to examine (i) the affective responses of normal‐weight (NW), overweight (OW), and OB middle‐aged sedentary women to exercise of increasing intensity and (ii) the relationship of affective responses to self‐efficacy and social physique anxiety. The women participated in a graded treadmill protocol to volitional exhaustion while providing ratings of pleasure–displeasure and perceived activation each minute. The Activation Deactivation Adjective Check List (AD ACL) was also completed before and after exercise. The affective responses of NW and OW women did not differ. However OB women gave lower pleasure ratings during the incremental protocol and reported lower Energy scores immediately after the protocol. Social physique anxiety, but not self‐efficacy, was inversely related to pleasure and energy. The lower levels of pleasure and energy experienced by OB than nonobese women could account in part for their dramatically low levels of PA participation. Modifying the cognitive antecedents of social physique anxiety might be a useful intervention strategy.     

Insulin Resistance is the Best Predictor of the Metabolic Syndrome in Subjects With a First‐Degree Relative With Type 2 Diabetes

Although obesity is associated with insulin resistance and the metabolic syndrome (MetS), some obese individuals are metabolically healthy. Conversely, some lean individuals are insulin resistant (IR) and at increased cardiometabolic risk. To determine the relative importance of insulin sensitivity, BMI and waist circumference (WC) in predicting MetS, we studied these two extreme groups in a high‐risk population. One thousand seven hundred and sixty six subjects with a first‐degree relative with type 2 diabetes were stratified by BMI and homeostasis model assessment of insulin resistance (HOMA_IR) into groups. IR groups had higher triglycerides, fasting glucose, and more diabetes than their BMI‐group insulin sensitive (IS) counterparts. Within both IS and IR groups, obesity was associated with higher HOMA_IR and diastolic blood pressure (BP), but no difference in other metabolic variables. MetS (Adult Treatment Panel III (ATPIII)) prevalence was higher in IR groups (P < 0.001) and more subjects met each MetS criterion (P < 0.001). Within each BMI category, HOMA_IR independently predicted MetS (P < 0.001) whereas WC did not. Within IS and IR groups, age and WC, but not BMI, were independent determinants of MetS (P < 0.001). WC was a less meaningful predictor of MetS at higher values of HOMA_IR. HOMA_IR was a better predictor of MetS than WC or BMI (receiver operating characteristic (ROC) area under the curve 0.76 vs. 0.65 vs. 0.59, P < 0.001). In conclusion, insulin sensitivity rather than obesity is the major predictor of MetS and is better than WC at identifying obese individuals with a healthier metabolic profile. Further, as many lean individuals with a first‐degree relative with type 2 diabetes are IR and metabolically unhealthy, they may all benefit from metabolic testing.