The Prevalence of Metabolically Healthy Obese Subjects Defined by BMI and Dual‐Energy X‐Ray Absorptiometry

Nearly one‐third of obese (OB) people are reported to be metabolically healthy based on BMI criteria. It is unknown whether this holds true when more accurate adiposity measurements are applied such as dual‐energy X‐ray absorptiometry (DXA). We compared differences in the prevalence of cardiometabolic abnormalities among adiposity groups classified using BMI vs. DXA criteria. A total of 1,907 adult volunteers from Newfoundland and Labrador participated. BMI and body fat percentage (%BF; measured using DXA) were measured following a 12‐h fasting period. Subjects were categorized as normal weight (NW), overweight (OW), or OB based on BMI and %BF criteria. Cardiometabolic abnormalities considered included elevated triglyceride, glucose, and high‐sensitivity C‐reactive protein (hsCRP) levels, decreased high‐density lipoprotein (HDL) cholesterol levels, insulin resistance, and hypertension. Subjects were classified as metabolically healthy (0 or 1 cardiometabolic abnormality) or abnormal (≥2 cardiometabolic abnormalities). We found low agreement in the prevalence of cardiometabolic abnormalities between BMI and %BF classifications (κ = 0.373, P < 0.001). Among NW and OW subjects, the prevalence of metabolically healthy individuals was similar between BMI and %BF (77.6 vs. 75.7% and 58.8 vs. 62.5%, respectively) however, there was a pronounced difference among OB subjects (34.0 vs. 47.7%, P < 0.05). Similar trends were evident using three additional definitions to characterize metabolically healthy individuals. Our findings indicate that approximately one‐half of OB people are metabolically healthy when classified using %BF criteria which is significantly higher than previously reported using BMI. Caution should therefore be taken when making inferences about the metabolic health of an OB population depending on the method used to measure adiposity.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Prevalence of Pre‐obesity and Obesity in Urban Adult Mexicans in Comparison with Other Large Surveys

Objective: 1. To estimate the prevalence of pre‐obesity and obesity in a 1992 to 1993 national survey of the Mexican urban adult population. 2. To compare our findings with other national surveys and with data for Mexican Americans. Research Methods and Procedures: The national representative sample of the Mexican urban adult population included 8462 women and 5929 men aged 20 to 69 years from 417 towns of >2500 people. Body mass index (BMI), calculated from measured weight and height, was classified using the World Health Organization categories of underweight (BMI < 18.5 kg/m²), normal weight (BMI 18.5 to 24.9 kg/m²), pre‐obesity (PreOB = BMI 25 to 29.9 kg/m²) and obesity (OB = BMI 30+ kg/m²). Estimates for Mexican Americans were calculated from U.S. survey data. Results: Overall, 38% of the Mexican urban adult population were classified as pre‐obese and 21% as obese. Men had a higher prevalence of pre‐obesity than women did at all ages, but women had higher values of obesity. Both pre‐obesity and obesity increased with age up to the age range brackets of 40 to 49 or 50 to 59 years for both men and women. Both pre‐obesity and obesity prevalence estimates were remarkably similar to data for Mexican Americans from 1982 through 1984. Comparison with other large surveys showed that countries differed more in the prevalence of obesity than of pre‐obesity, leading to differences in the PreOB/OB ratio, and that countries also differed in the gender ratio (female/male) for both pre‐obesity and obesity. Discussion: Pre‐obesity and obesity were high in our population and increased with age. Our approach of characterizing large surveys by PreOB/OB and gender ratios appeared promising.     

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.     

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.     

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.     

Bioelectrical impedance underestimates total and truncal fatness in abdominally obese women

Objective: To compare estimates of total and truncal fatness from eight‐electrode bioelectrical impedance analysis equipment (BIA₈) with those from DXA in centrally obese women. The secondary aim was to examine BMI and waist circumference (WC) as proxy measures for percentage total body fat (%TBF) and truncal body fat percentage (tr%BF). Research Methods and Procedures: This was a cross‐sectional study of 136 women (age, 48.1 ± 7.7 years; BMI, 30.4 ± 2.9 kg/m²; %TBF_DXA, 46.0 ± 3.7%; WC, 104 ± 8 cm). Fatness was measured by DXA and Tanita BC‐418 equipment (Tanita Corp., Tokyo, Japan). Agreement among methods was assessed by Bland‐Altman plots, and regression analysis was used to evaluate anthropometric measures as proxies for total and abdominal fatness. Results: The percentage of overweight subjects was 41.9%, whereas 55.9% of the subjects were obese, as defined by BMI, and all subjects had a WC exceeding the World Health Organization cut‐off point for abdominal obesity. Compared with DXA, the BIA₈ equipment significantly underestimated total %BF (?5.0; ?3.6 to ?8.5 [mean; 95% confidence interval]), fat mass (?3.6; ?3.9 to ?3.2), and tr%BF (?8.5; ?9.1 to ?7.9). The discrepancies between the methods increased with increasing adiposity for both %TBF and tr%BF (both p < 0.001). Variation in BMI explained 28% of the variation in %TBF_DXA and 51% of %TBF_BIA8. Using WC as a proxy for truncal adiposity, it explained only 18% of tr%BF_DXA variance and 27% of tr%BF_BIA8 variance. The corresponding figures for truncal fat mass were 49% and 35%, respectively. No significant age effects were observed in any of the regressions. Discussion: BIA₈ underestimated both total and truncal fatness, compared with DXA, with higher dispersion for tr%BF than %TBF. The discrepancies increased with degree of adiposity, suggesting that the accuracy of BIA is negatively affected by obesity.     

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.     

Comparison of body composition methods in obese African-American women

Objective : To compare the accuracy of percentage body fat (%BF) estimates between bioelectrical impedance analysis (BIA) and DXA in obese African‐American women. Research Methods and Procedures : Fifty‐five obese African‐American women (mean age, 45 years; mean BMI, 38; mean %BF, 48%) were studied. BF was assessed by both BIA (RJL Systems BIA 101Q; RJL Systems, Clinton Township, MI) and DXA (Hologic QDR‐2000 Bone Densitometer; Hologic Inc., Bedford, MA). Generalized and ethnicity‐ and obese‐specific equations were used to calculate %BF from the BIA. Bland‐Altman analyses were used to compare the agreement between the BIA and the DXA, with the DXA serving as the criterion measure. Results : Two of the generalized equations provided consistent estimates across the weight range in comparison with the DXA estimates, whereas most of the other equations increasingly underestimated %BF as BF increased. One of the generalized and one of the ethnicity‐specific equations had mean differences that were not significantly different from the DXA value. Discussion : The findings show that the Lukaski equation provided the most precise and accurate estimates of %BF in comparison with the QDR 2000 and provide preliminary support for the use of this equation for obese African‐American women.     

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.     

Oxidative Stress in Normal‐Weight Obese Syndrome

The normal‐weight obese (NWO) syndrome was identified in women whose body weight (BW) and BMI are normal but whose fat mass (FM) is >30%. In these subjects, an early inflammatory status has been demonstrated. The aim was to verify whether oxidative stress occurs in NWO. Sixty age‐matched white Italian women were studied and subdivided as follows: 20 normal‐weight individuals (NW) (BMI <25 kg/m²; FM% <30%); 20 NWO (BMI <25 kg/m²; FM% >30%); 20 preobese‐obese (OB) (BMI >25 kg/m²; FM% >30%). Anthropometric, body composition (by dual‐energy X‐ray absorptiometry) variables, plasma levels of some cytokines, reduced glutathione (GSH), lipid hydroperoxide (LOOH), nitric oxide (NO) metabolites (NO₂^?/NO₃^?), antioxidant nonproteic capacity (ANPC) were measured and compared between groups. Glucose and lipid metabolism parameters were assessed. GSH and NO₂^?/NO₃^? levels resulted lower in OB and NWO compared to NW (P < 0.01). LOOH levels resulted higher in OB and NWO (P < 0.01). ANPC in NWO was lower than NW but higher with respect to OB (P < 0.01). Correlation analysis revealed strong associations between GSH levels and BW, BMI, FM% (R = ?0.45, at least P < 0.05); waist circumference (W) (R = ?0.33, P < 0.05); FFM% (R = 0.45, P < 0.01); IL‐1α, IL‐6, IL‐10, IL‐15 (R = ?0.39, ?0.33, ?0.36 ?0.34, respectively, P < 0.05); triglycerides (R = ?0.416, P < 0.05). LOOH levels were negatively related to FFM% (R = ?0.413, P < 0.05) and positively to FM%, IL‐15, TNF‐α, insulin, total cholesterol, low‐density lipoprotein cholesterol, and triglycerides (R = 0.408, R = 0.502, R = 0.341, R = 0.412, R = 0.4036, R = 0.405, R = 0.405, respectively, P < 0.05). The study clearly indicates that NWO, besides being in early inflammatory status, are contextually exposed to an oxidative stress related to metabolic abnormalities occurring in obesity.     

Social influences are associated with BMI and weight loss intentions in young adults

Christakis and colleagues have shown that health behaviors cluster in social networks and suggest social norms may account for the clustering. This study examined: (i) whether obesity clusters among young adults and whether social norms do in fact account for the clustering, and (ii) among overweight/obese (OW/OB) young adults, whether number of social contacts trying to lose weight is associated with weight loss intentions and whether social norms for weight loss account for this effect. Normal weight (NW) and OW/OB young adults (N = 288; 66% female; 75% white) completed measures assessing number of OW social contacts and social norms for obesity. OW/OB young adults also indicated number of OW social contacts currently trying to lose weight, social norms for weight loss, and weight loss intentions. Compared to NW, OW/OB young adults were more likely to have OW romantic partners and best friends and had more OW casual friends and family members (Ps < 0.05), but social norms for obesity did not differ between groups, and social norms did not mediate the relationship between OW social contacts and participants' weight status. However, among OW/OB young adults, having more social contacts trying to lose weight was associated with greater intention to lose weight (r = 0.20, P = 0.02) and social norms for weight loss fully mediated this effect (P < 0.01). This study is the first to show that social contacts and normative beliefs influence weight status and intentions for weight control in young adults. Findings underscore the importance of targeting social influence in the treatment and prevention of obesity in this high-risk age group.     

Relationships Between the Body Mass Index and Body Composition

The aims of this study were to evaluate the Body Mass Index (BMI) (weight/stature²) as a proxy for percent body fat (%BF) and to determine its association with fat-free mass (FFM). Multivariate analysis of variance and partial correlations were used to examine relationships between BMI and %BF and FFM from densitometry for 504 men and 511 women, aged 20 to 45 years. Sensitivity/specificity analyses used cut offs of 28 kg/m² in men and 26 kg/m² in women for BMI, and 25% in men and 33% in women for %BF. Significantly higher associations existed in each gender between BMI and %BF in the upper BMI tertile than in the lower BMI tertiles. In the lower BMI tertiles, correlations between BMI and FFM were approximately twice as large as those between BMI and %BF. The BMI correctly identified about 44% of obese men, and 52% of obese women when obesity was determined from %BF. BMI is an uncertain diagnostic index of obesity. Results of Receiver Operator Characteristic (ROC) analyses using %BF and total body fat, both provided a BMI of 25 kg/m² in men and 23 kg/m² in women as diagnostic screening cut offs for obesity.