The relationship between body mass index and per cent body fat in the severely obese

Body composition predicts prognosis of hepatocellular carcinoma patients undergoing immune checkpoint inhibitors

PURPOSE

Immune checkpoint inhibitors (ICIs) with anti-PD-1/PD-L1 antibody are promising treatments for hepatocellular carcinoma (HCC), but lack reliable biomarkers of response. In the present study, we aimed to investigate the correlation between pre-treatment body composition measures (muscle, adipose, etc.) and the prognosis of patients with HCC treated with ICIs.

METHODS

We measured the total area of all skeletal muscles, total adipose tissue area, subcutaneous adipose tissue area, and visceral adipose tissue area at the level of the third lumbar vertebra using quantitative CT. Then, we calculated the skeletal muscle index, visceral adipose tissue index, subcutaneous adipose tissue index (SATI), and total adipose tissue index. The Cox regression model was used to determine the independent factors of the patient prognosis and construct a nomogram to predict survival. The consistency index (C-index) and calibration curve were used to determine the predictive accuracy and discrimination ability of the nomogram.

RESULTS

Multivariate analysis revealed that the SATI (high- vs. low SATI; HR 0.251; 95% CI 0.109-0.577; P = 0.001), sarcopenia (sarcopenia vs. no sarcopenia; HR 2.171; 95% CI 1.100-4.284; P = 0.026), and portal vein tumor thrombus (PVTT) (PVTT vs. No PVTT; HR 2.429; 95% CI 1. 197-4. 929; P = 0.014) were indicated as independent prognostic factors for OS in multivariate analysis. Multivariate analysis indicated that Child-Pugh class (HR 0.477, 95% CI 0.257-0.885, P = 0.019) and sarcopenia (HR 2.376, 95% CI 1.335-4.230, P = 0.003) were independent prognostic factors of PFS. We established a nomogram using SATI, SA, and PVTT to predict the 12-month and 18-month survival probability of HCC patients treated with ICIs. The C-index of the nomogram was 0.754 (95% CI 0.686-0.823), and the calibration curve confirmed that the predicted results were in good agreement with the actual observations.

CONCLUSION

Subcutaneous adipose and sarcopenia are significant prognostic factors of patients with HCC receiving ICIs. A nomogram based on body composition parameters and clinical factors could well predict survival in HCC patients treated with ICIs.

Obesity measures in the Kiribati population: a need to reclassify body mass index cut-points

BACKGROUND

Obesity is a public health problem in Micronesia. The objective of the study was to assess obesity, the relationship between body mass index (BMI) and body fat percentage (BF%) among adults, and determine the appropriate BMI cut-points in Kiribati.

METHODS

A cross-sectional study was undertaken among 483 adults randomly selected from South Tarawa (ST) and Butaritari (BT). Weight, height, BF% and physical activity level (PAL) was measured using standard methods. Linear and quadratic regression analyses were conducted to assess the association between BF% and BMI whilst controlling for age and gender. Receiver operating characteristics (ROC) curve analyses were used to assess whether for the Kiribati population alternative BMI cut-off points for obesity are needed.

RESULTS

Approximately 75% of participants were obese using standard BMI and BF% cut-offs, with the highest prevalence observed in South Tarawa. BF% was significantly (p < 0.001) and positively associated with age (males, r = 0.78; females, r = 0.67; p < 0.001) and BMI. Based on ROC-curve analyses the BMI cut-offs for predicting high BF% among I-Kiribati people were 24.5 kg/m2 for males and 32.9 kg/m2 for females.

CONCLUSIONS

In conclusion, the majority of adults in Kiribati were either obese or overweight and had high BF%. We suggest that ethnic-specific BMI cut-points to define obesity for the population of Kiribati may be more appropriate than the currently used international cut-points.

Adipose Tissue Distribution and Cardiovascular Disease Risk Among Breast Cancer Survivors

PURPOSE

Cardiovascular disease (CVD) is a major source of morbidity and mortality among breast cancer survivors. Although body mass index (BMI) is associated with CVD risk, adipose tissue distribution may better identify patients with a high risk of CVD after breast cancer.

METHODS

Among 2,943 patients with nonmetastatic breast cancer without prior CVD, we used International Classification of Diseases (9th and 10th revisions) codes to identify incidence of nonfatal stroke, myocardial infarction, heart failure, or CVD death. From clinically acquired computed tomography scans obtained near diagnosis, we measured visceral adiposity (centimeters squared), subcutaneous adiposity (centimeters squared), and intramuscular adiposity (fatty infiltration into muscle [Hounsfield Units, scored inversely]). We estimated hazard ratios (HRs) and 95% CIs per SD increase in adiposity accounting for competing risks and adjusting for demographics, smoking, cancer treatment, and pre-existing CVD risk factors.

RESULTS

Mean (SD) age was 56 (12) years. Over a median follow-up of 6 years, 328 CVD events occurred. Each SD increase in visceral or intramuscular adiposity was associated with an increase in CVD risk (HR, 1.15 [95% CI, 1.03 to 1.29] and HR, 1.21 [95% CI, 1.06 to 1.37]), respectively). Excess visceral and intramuscular adiposity occurred across all BMI categories. Among normal-weight patients, each SD greater visceral adiposity increased CVD risk by 70% (HR, 1.70 [95% CI, 1.10 to 2.62]).

CONCLUSION

Visceral and intramuscular adiposity were associated with increased CVD incidence after breast cancer diagnosis, independent of pre-existing CVD risk factors and cancer treatments. The increased CVD incidence among normal-weight patients with greater visceral adiposity would go undetected with BMI alone. Measures of adipose tissue distribution may help identify high-risk patients and tailor CVD prevention strategies.

The Importance of Body Composition in Explaining the Overweight Paradox in Cancer-Counterpoint

Despite a greater risk of cancer associated with higher BMI, overweight (BMI 25-<30 kg/m²) and class I obese (BMI 30-<35 kg/m²) patients often have a paradoxically lower risk of overall mortality after a cancer diagnosis, a phenomenon called the "obesity paradox." Only when patients exceed a BMI ≥35 kg/m² are elevations in mortality risk consistently noted. This paradox has been dismissed as the result of methodologic bias, which we will describe and debate here. However, even if such bias influences associations, there is growing evidence that body composition may in part explain the paradox. This phenomenon may more accurately be described as a BMI paradox. That is, BMI is a poor proxy for adiposity and does not distinguish muscle from adipose tissue, nor describe adipose tissue distribution. Low muscle mass is associated with higher risk of recurrence, overall and cancer-specific mortality, surgical complications, and treatment-related toxicities. Patients with who are overweight or obese have on average higher levels of muscle than their normal-weight counterparts. Also, there is some evidence that patients with moderate levels of subcutaneous adipose tissue may have lower mortality. More research utilizing body composition is needed to clarify the effects of adiposity on cancer mortality. Cancer Res; 78(8); 1906-12. ©2018 AACR.

Plasma lipidome variation during the second half of the human lifespan is associated with age and sex but minimally with BMI

Recent advances in mass spectrometry-based techniques have inspired research into lipidomics, a subfield of ‘–omics’, which aims to identify and quantify large numbers of lipids in biological extracts. Although lipidomics is becoming increasingly popular as a screening tool for understanding disease mechanisms, it is largely unknown how the lipidome naturally varies by age and sex in healthy individuals. We aimed to identify cross-sectional associations of the human lipidome with ‘physiological’ ageing, using plasma from 100 subjects with an apolipoprotein E (APOE) E3/E3 genotype, and aged between 56 to 100 years. Untargeted analysis was performed by liquid chromatography coupled-mass spectrometry (LC-MS/MS) and data processing using LipidSearch software. Regression analyses confirmed a strong negative association of age with the levels of various lipid, which was stronger in males than females. Sex-related differences include higher LDL-C, HDL-C, total cholesterol, particular sphingomyelins (SM), and docosahexaenoic acid (DHA)-containing phospholipid levels in females. Surprisingly, we found a minimal relationship between lipid levels and body mass index (BMI). In conclusion, our results suggest substantial age and sex-related variation in the plasma lipidome of healthy individuals during the second half of the human lifespan. In particular, globally low levels of blood lipids in the ‘oldest old’ subjects over 95 years could signify a unique lipidome associated with extreme longevity.

A comparison of body mass index and percent body fat as predictors of cardiovascular risk factors

BACKGROUND

Cardiovascular disease (CVD) is an important cause of global mortality and morbidity. Body mass index (BMI) is the measure of adiposity that is used most frequently in CVD risk algorithms.

AIMS

We aimed to assess the relationship between several CVD risk factors (RFs) and percent body fat (PBF), and to compare the predictive values obtained using PBF for these cardiovascular RFs with the values obtained using BMI. The CVD RFs included, hypertension (HTN), diabetes mellitus (DM) and the presence of dyslipidemia (DLP).

METHODS AND MATERIALS

The data were derived from the MASHAD study, a cohort study of 9704 volunteers, aged 35-65 years and living in the city of Mashhad. Based on BMI and PBF values, subjects were classified into 4 groups; group 1 (low or normal BMI and PBF, N = 1670), group 2 (low or normal BMI but high PBF, N = 992), group 3 (high BMI and low or normal PBF, N = 837), and group 4 (high BMI and PBF, N = 6245). Chi-square, covariance and logistic regression were used to analyze the data at a significance level of 0.05.

RESULTS

There was an increasing trend from group 1 to group 4 for the mean values of all CVD RFs and their prevalence. There were significant differences in the frequency of a low HDL-C, this was substantially higher in Group 3 (38.6% in Group 3 versus 12.2% in Group 2); the frequency of a high serum TG (24% in Group 3 versus 9.9% in Group 2) and the frequency of dyslipidemia overall (56.2% in Group 3 and 28.8% in Group 2) (P-value<0.001 for all comparisons). The frequency of hypertension (22.9% in Group 3 versus 16.2% in Group 2) and IFG (8.5% in Group 3 versus 5.0% in Group 2) were also substantially higher in Group 3 compared to Group 2 (P-value<0.001 for both comparisons). All the mean values for the RFs were higher in group 3 from group 2 except HDL-C. When Group 1 was used as a reference and calculated OR of any RF for any group 2-4 rather than group 1, OR for all RF in group 3 was higher from group 2.

CONCLUSION

The differences in frequency, means and OR of RFs between Groups 2 and 3 showed a differential impact of a high BMI or high PBF. Compared to PBF, BMI may be a better predictor for several RFs for CVD.

New anthropometric indices or old ones: Which is the better predictor of body fat?

BACKGROUND

The percent and distribution of body fat are important factors in the pathogenesis of numerous diseases. Our aim was to investigate common anthropometric indices in their relationship with body fat content.

METHODS

In a cross-sectional study 1360 healthy individuals (580 men and 780 women) in a cluster sampling, from Ahvaz, Iran, body fat content (using bioelectrical impedance) and anthropometric measurements [weight, waist circumference, a body shape index, abdominal volume index, body adiposity index, conicity, body mass index, hip circumference, waist to hip ratio and waist to height ratio] was obtained. The ROC curve analysis was used to compare each index with body fat percent.

RESULTS

Significant difference was found between men and women in all anthropometric parameters (p < 0.001). Women displayed higher percentages in the overweight and obese categories (33.6% vs. 32.9% and 26.4% vs. 22.1%, respectively). In both men and women, the strongest correlations were seen between body fat percent and BMI, AVI and WHtR (r>7.9 and p<0.001). BMI, WHtR and AVI in men and BAI, BMI and WHtR in women showed the most accuracy for estimating body fat percent, respectively.

CONCLUSION

All anthropometric parameters could predict body fat percent with relatively good power, however BMI, WHtR and AVI are more powerful predictors. Based on our findings, we suggest using the AVI and WHtR instead of other indexes, as they are better able to assess the accumulation of fat in the abdominal area and are able to more accurately assess body fat percent, which are indicators of chronic disease.

Specific BIVA recognizes variation of body mass and body composition: Two related but different facets of nutritional status

OBJECTIVE

The aim of this study was to demonstrate the different information provided by body mass index (BMI) in combination with specific bioelectrical impedance vector analysis (specific BIVA) in the measure of relative body fat.

METHODS

Anthropometric and bioelectrical values and dual-energy x-ray absorpitometry measurements from a sample of 1590 US adults of both sexes were retrieved from the National Health and Nutrition Examination Survey 2003-2004. The sample distribution of the BMI of each sex was divided into deciles. Quartiles were calculated for percent fat mass (FM%) after stratifying by BMI deciles. Body composition and bioelectrical characteristics of groups below the first and above the third quartile were compared using analysis of variance and the Hotelling's T-square test.

RESULTS

BMI and specific BIVA showed a different accuracy in detecting body composition variations: BMI showed similar values in groups represented by different FM percentages, whereas the bioelectrical differences were statistically significant. The mean impedance vectors corresponding to cases below the first FM% quartiles were shorter and located on the left side of the ellipses (the region of higher fat-free mass), whereas those above the third FM% quartiles were on the right and toward the upper pole (the region of higher FM%).

CONCLUSIONS

Specific BIVA is a technique for the evaluation of body composition which can add relevant information regarding BMI.

Prevalence of Injury in Occupation and Industry: Role of Obesity in the National Health Interview Survey 2004 to 2013

OBJECTIVES

The aim of this study was to estimate prevalence of injury by occupation and industry and obesity's role.

METHODS

Self-reported injuries were collected annually for US workers during 2004 to 2013. Prevalence ratios (PRs) and 95% confidence intervals (CIs) were obtained from fitted logistic regression models.

RESULTS

Overall weighted injury prevalence during the previous three months was 77 per 10,000 workers. Age-adjusted injury prevalence was greatest for Construction and Extraction workers (169.7/10,000) followed by Production (160.6) among occupations, while workers in the Construction industry sector (147.9) had the highest injury prevalence followed by the Agriculture/Forestry/Fishing/Mining/Utilities sector (122.1). Overweight and obese workers were 26% to 45% more likely to experience injuries than normal-weight workers.

CONCLUSION

The prevalence of injury, highest for Construction workers, gradually increased as body mass index levels increased in most occupational and industry groups.

Genetics of nonsyndromic obesity

PURPOSE OF REVIEW

Common obesity is widely regarded as a complex, multifactorial trait influenced by the 'obesogenic' environment, sedentary behavior, and genetic susceptibility contributed by common and rare genetic variants. This review describes the recent advances in understanding the role of genetics in obesity.

RECENT FINDINGS

New susceptibility loci and genetic variants are being uncovered, but the collective effect is relatively small and could not explain most of the BMI heritability. Yet-to-be identified common and rare variants, epistasis, and heritable epigenetic changes may account for part of the 'missing heritability'. Evidence is emerging about the role of epigenetics in determining obesity susceptibility, mediating developmental plasticity, which confers obesity risk from early life experiences. Genetic prediction scores derived from selected genetic variants, and also differential DNA methylation levels and methylation scores, have been shown to correlate with measures of obesity and response to weight loss intervention. Genetic variants, which confer susceptibility to obesity-related morbidities like nonalcoholic fatty liver disease, were also discovered recently.

SUMMARY

We can expect discovery of more rare genetic variants with the advent of whole exome and genome sequencing, and also greater understanding of epigenetic mechanisms by which environment influences genetic expression and which mediate the gene-environment interaction.

Melanocortin 3 receptor gene and melanocortin 4 receptor gene mutations: the Asian Perspective

Melanocortin 4 receptor (MC4R) deficiency resulting from disruption of one or both MC4R alleles represents the commonest monogenic form of human obesity to date. Human MC4R deficiency was reported to affect 4 and 5.8% of severely obese French and British populations respectively. However, studies elsewhere reported low incidence of MC4R mutations in their obese populations. The significance of MC4R mutations in Asian obese populations has not been adequately examined, though small studies in Japan, China, and Singapore reported few or no pathogenic mutations, suggesting a low prevalence in this part of the world. There were also few common mutations described across populations, suggesting a relative lack of founder effect. The pathogenic role of melanocortin 3 receptor gene (MC3R) mutations in human obesity is not as well described and accepted as MC4R mutations, though it is gradually gaining ground. Two common single nucleotide polymorphisms Thr6Lys and Val81Ile within the coding region were associated with higher body fat and leptin levels in obese children, supported by impaired signaling activity in vitro. There were also reports of missense mutations enriched in obese populations. While MC3R mutations are unlikely to result in an autosomal dominant form of monogenic obesity given the lack of strong co-segregation in family studies, the studies so far provided evidence that MC3R can be one of the genes which contributes to increased adiposity, and exert an effect on the human phenotype.

Obesity in young-adult Nigerians: variations in prevalence determined by anthropometry and bioelectrical impedance analysis, and the development of % body fat prediction equations

Background

Overweight/obesity is a growing global public health concern. The variations in the prevalence of overweight/obesity, defined by Body Mass Index (BMI), Waist Circumference (WC), Waist-to-Height Ratio (WHtR), Waist-to-Hip Ratio (WHpR) and Bioelectrical Impedance Analysis (BIA), were studied and a prediction equation for % body fat (%BF) developed.

Methods

A total of 1584 subjects (56.4% males) were recruited for the study. Data on age, gender, height, weight, hip circumference and WC were collected from the subjects using standard protocols. BMI, WHtR and WHpR were derived using standard equations. %BF was measured using a BIA device (Omron BF-400). Appropriate statistical tools were used for the data analysis.

Results

The prevalence of overweight/obesity in the population was 28.4% (36.3% for males; 22.6% for females) (BIA); 20.7% (17.5% for males; 24.8% for females) (BMI); 7.5% (1.3% for males; 16.1% for females) (WC); 2.9% (4.3% for males; 1.2% for females) (WHpR); and 15.4% (14.8% for males; 16.2% females) (WHtR). Taking BIA as the reference point, WC misclassified overweight/obesity the most for males (35%), while for the females, WHpR misclassified both disorders the most (21.4%). Correlation studies showed that only BMI correlated significantly, albeit weakly, with %BF among the males, whereas all the anthropometric measures, but WHpR correlated significantly with % body fat in females. Two prediction equations for %BF were generated, and %BF predicted with the two equations correlated significantly (P < 0.001) with that measured by BIA.

Conclusion

The prevalence of overweight/obesity in this population vary widely depending on the definition used. The developed prediction equations could be useful in resource-poor settings, but require validation.

Percent body fat is a better predictor of cardiovascular risk factors than body mass index

The objective of the present study was to evaluate the predictive values of percent body fat (PBF) and body mass index (BMI) for cardiovascular risk factors, especially when PBF and BMI are conflicting. BMI was calculated by the standard formula and PBF was determined by bioelectrical impedance analysis. A total of 3859 ambulatory adult Han Chinese subjects (2173 males and 1686 females, age range: 18-85 years) without a history of cardiovascular diseases were recruited from February to September 2009. Based on BMI and PBF, they were classified into group 1 (normal BMI and PBF, N = 1961), group 2 (normal BMI, but abnormal PBF, N = 381), group 3 (abnormal BMI, but normal PBF, N = 681), and group 4 (abnormal BMI and PBF, N = 836). When age, gender, lifestyle, and family history of obesity were adjusted, PBF, but not BMI, was correlated with blood glucose and lipid levels. The odds ratio (OR) and 95% confidence interval (CI) for cardiovascular risk factors in groups 2 and 4 were 1.88 (1.45-2.45) and 2.06 (1.26-3.35) times those in group 1, respectively, but remained unchanged in group 3 (OR = 1.32, 95%CI = 0.92-1.89). Logistic regression models also demonstrated that PBF, rather than BMI, was independently associated with cardiovascular risk factors. In conclusion, PBF, and not BMI, is independently associated with cardiovascular risk factors, indicating that PBF is a better predictor.

Adiposity rather than BMI determines metabolic risk

BACKGROUND AND AIM

There is increasing evidence suggesting that WHO body mass index (BMI) cut-off values are outdated and should not be applied to different population. To overcome misclassifications, direct measurements of percentage body fat (PBF) would be a better tool for preobesity and obesity diagnosis. The aim of this study was to analyze the body composition in a adult population in Centre-South of Italy, by age and gender, and to verify the accordance between BMI and PBF cut-off points for health status classification.

METHODS

The total subject pool cover a total of 4408 participants adults. A completed screening of anthropometry and body composition by Dual X-ray Absorptiometry, (DXA) was assessed on 3.258 subjects.

RESULTS

Distributions and quantitative reliable estimates of PBF, total body fat and lean, according to gender and age are provided. The prevalence of "at risk" subjects (preobese and obese) was 69% and 85%, for men and women respectively, according to PBF cut-off points. The agreement of BMI and PBF categories resulted low for the total and male population, even scarce for female population (all P ≤ 0.001). The false negative classification of BMI was stronger for women than men and for younger than older subjects.

CONCLUSIONS

Screening for adiposity in subjects with a normal BMI could better identify those at higher risk for cardiometabolic disturbances and cardiovascular mortality. The herein used cut-offs points of PBF, by age and gender, may provide a useful reference in clinical settings and public health services, in particular for the Italian Caucasian population.

Fuzzy obesity index (MAFOI) for obesity evaluation and bariatric surgery indication

Background

The Miyahira-Araujo Fuzzy Obesity Index (MAFOI) for being used as an alternative in bariatric surgery indication (BSI) is validated in this paper. The search for a more accurate method to evaluate obesity and to indicate a better treatment is important in the world health context. Body mass index (BMI) is considered the main criteria for obesity treatment and BSI. Nevertheless, the fat excess related to the percentage of Body Fat (%BF) is actually the principal harmful factor in obesity disease that is usually neglected. The aim of this research is to validate a previous fuzzy mechanism by associating BMI with %BF that yields the Miyahira-Araujo Fuzzy Obesity Index (MAFOI) for obesity evaluation, classification, analysis, treatment, as well for better indication of surgical treatment.

Methods

Seventy-two patients were evaluated for both BMI and %BF. The BMI and %BF classes are aggregated yielding a new index (MAFOI). The input linguistic variables are the BMI and %BF, and the output linguistic variable is employed an obesity classification with entirely new types of obesity in the fuzzy context, being used for BSI, as well.

Results

There is gradual and smooth obesity classification and BSI criteria when using the Miyahira-Araujo Fuzzy Obesity Index (MAFOI), mainly if compared to BMI or %BF alone for dealing with obesity assessment, analysis, and treatment.

Conclusion

The resulting fuzzy decision support system (MAFOI) becomes a feasible alternative for obesity classification and bariatric surgery indication.

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.

The relation of BMI and skinfold thicknesses to risk factors among young and middle-aged adults: the Bogalusa Heart Study

OBJECTIVE

Although adverse levels of cardiovascular disease risk factors are related to skinfold thicknesses and BMI among adults, the relative strengths of these associations are unknown. We examine whether the triceps and subscapular skinfold thicknesses are more strongly related to adult levels of lipids, fasting insulin and blood pressure than BMI.

DESIGN AND SUBJECTS

Cross-sectional (n =3318) and longitudinal (n =1593) analyses of 18- to 44-year-olds examined in the Bogalusa Heart Study from 1983 to 2002. Principal components analysis was used to derive a summary index of the six examined risk factors (triglycerides, low- and high-density lipoprotein cholesterol, insulin, and systolic and diastolic blood pressures).

RESULTS

The magnitudes of the differences were generally small, but all comparisons indicated that BMI was at least as strongly related to adverse risk factor levels as was the sum of subscapular and triceps skinfold thicknesses (SF sum). For example, adjusted cross-sectional associations with the risk factor summary were r = 0.55 (BMI) and r = 0.49 (SF sum), p < 0.001 for difference between correlations. Similar differences were seen in longitudinal analyses, with changes in the risk factor summary being more strongly associated with changes in BMI (r =0.50) than with changes in the SF sum (r = 0.38).

CONCLUSION

BMI appears to be at least as accurate as skinfold thicknesses in identifying metabolic risk among adults. The advantages of BMI should be considered in the design and interpretation of clinical and epidemiologic studies.

The relationship between BMI and percent body fat, measured by bioelectrical impedance, in a large adult sample is curvilinear and influenced by age and sex

OBJECTIVE

The study aimed to establish the effects of age, gender and age-gender interactions on BMI-% fat relationships over a wide range of BMI and age. It also aimed to examine controversies regarding linear or curvilinear BMI-% fat relationships.

METHODS

Body composition was measured using validated bio-impedance equipment (Bodystat) in a large self-selected sample of 23,627 UK adults aged 18-99 (99% ≤70) years, of which 11,582 were males with a mean BMI of 26.3±4.7 (sd) kg/m(2), and 12,044 females, with a mean BMI of 25.7±5.1 kg/m(2). Multiple regression analysis was used.

RESULTS

BMI progressively increased with age in women and plateaued between 40 and 70 years in men. At a fixed BMI, body fat mass increased with age (1.9 kg/decade), as did % fat (1.1-1.4% per decade). The relationship between BMI and % fat was found to be curvilinear (quadratic) rather than linear, with a weaker association at lower BMI. There was also a small but significant age-gender interaction.

CONCLUSION

The association between BMI and % body fat is not strong, particularly in the desirable BMI range, is curvilinear rather than linear, and is affected by age.

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.

Relationship between growth hormone/insulin-like growth factor-1 axis integrity and voluntary weight loss after gastric banding surgery for severe obesity

BACKGROUND

The aim of this observational study was to determine, in a retrospective analysis, whether growth hormone (GH) and insulin-like growth factor-1 (IGF-1) at baseline or changes in the GH/IGF-1 axis after laparoscopic adjustable gastric banding (LAGB) is associated with weight loss and body composition changes in severely obese nondiabetic patients.

METHODS

Weight loss (expressed as percent excess weight loss [EWL%]), anthropometry, body composition by bioelectrical impedance analysis (BIA), serum IGF-1, and GH peak after GH-releasing hormone (GHRH) plus arginine (ARG) test were measured and expressed as standard deviation scores (SDS) of reference values in 104 women and 36 men, age (mean +/- SD) 34 +/- 11 and 30.2 +/- 11 years, and BMI 44 +/- 5.7 and 39 +/- 3.2, respectively, before and 6 months after LAGB.

RESULTS

After LAGB, 25% of women and 22.5% of men had GH deficiency, while 30.8% of women and 33.3% of men had IGF-1 deficiency or insufficiency. The median EWL was 36.8% in women and 40.0% in men. In both genders, percent decrease of waist circumference, EWL, and fat mass (FM) and percent increase of fat-free mass (FFM) was greater in patients with normal GH secretion and IGF-1 levels. The GH peak after GHRH + ARG, IGF-1 levels, and IGF-1 SDS were inversely correlated with EWL% (r = -0.50, r = -0.53, and r = -0.42, respectively; p < 0.0001) and percent FM (r = -0.41, r = -0.36, and r = -0.35, respectively; p < 0.0001). In stepwise linear regression analysis, the GH peak after GHRH + ARG was the major determinant of EWL% (p < 0.0001) and FM (p = 0.001).

CONCLUSIONS

The efficacy of LAGB was greater in the patients with a normal GH response to GHRH + ARG and with normal IGF-1 levels. The percent of FM, FFM, and EWL were significantly correlated with the GH response to GHRH + ARG and with IGF-1 levels.

Relation of obesity to atrial fibrillation after isolated coronary artery bypass grafting

The impact of obesity on risk of atrial fibrillation (AF) after coronary artery bypass grafting (CABG) is poorly understood. This study was performed to investigate the relation between body mass index (BMI; kilograms per square meter) or body surface area (BSA; square meters) and AF after CABG. Postoperative AF was assessed in a cohort of 7,027 consecutive patients without preoperative AF undergoing isolated CABG at Baylor University Medical Center from January 1, 1997 to December 31, 2006. Two propensity-adjusted models controlling for risk factors identified by the Society of Thoracic Surgeons and other clinical/nonclinical details were used. After adjustment, BMI and BSA (modeled using smoothing techniques to avoid categorization) were strongly associated (p <0.0001) with postoperative AF. Although evidence existed that gender was associated with AF (p <0.0001 and p = 0.1088 for BSA and BMI models, respectively), there was no indication that the effect of BMI or BSA on postoperative AF varied by gender. In conclusion, this study demonstrates that increased BMI and BSA are associated with a higher risk of AF after CABG and that risk for men is higher for the entire BSA spectrum and for extreme values of BMI.

The Role of Leptin-Melanocortin System and Human Weight Regulation: Lessons from Experiments of Nature

Introduction: Common obesity is a multi-factorial trait, contributed by the “obesogenic” environment of caloric abundance and increasing automation, sedentary lifestyle and an underlying genetic susceptibility. There have been major advances in the past decade in our understanding of the human weight regulation mechanism and pathogenesis of obesity, abetted by discoveries of genetic defects which lead to human obesity. Materials and Methods: Reports of genetic mutations causing obesity in humans and murine models were reviewed Results: Humans with genetic defects resulting in leptin deficiency, leptin receptor deficiency, pro-opiomelanocortin deficiency (POMC), and melanocortin 4 receptor (MC4R) deficiency developed severe obesity as the dominant phenotypic feature, though these are rare autosomal recessive conditions, except MC4R deficiency which is inherited in an autosomal co-dominant fashion. Common and rare variants of the POMC and melanocortin 3 receptor genes may be pre-disposing factors in the development of common obesity. Recent reports of human obesity associated with thyrosine kinase B (TrkB) defect and brain derived neurotrophic factor (BDNF) disruption, coupled with other murine studies, supported the role of BDNF/TrkB as effectors downstream of the melanocortin receptors. Conclusions: Despite exciting discoveries of single gene mutations resulting in human obesity, most cases of obesity are likely the result of subtle interactions of several related genetic variants with environmental factors which favour the net deposition of calories as fat, culminating in the obese phenotype. The mechanisms of action of these genes in the development of obesity are now being examined, with the aim of eventually discovering a therapeutic intervention for obesity. Key words: Leptin, Melanocortin, Obesity

Factors affecting outcome after total knee arthroplasty in patients with diabetes mellitus

PURPOSE

To compare the clinical outcome and complications following total knee arthroplasty (TKA) in diabetic and non-diabetic patients, and to identify diabetes-related risk factors for negative outcomes.

MATERIALS AND METHODS

222 primary TKAs in patients with diabetes were evaluated using Knee Society scores and Hospital for Special Surgery score. Postoperative complications were reviewed retrospectively. The mean follow-up was 53.2 months. The effect of diabetes-related factors and comparison with a matched control group were analyzed statistically.

RESULTS

Significant improvements were noted in all the scores after TKA (p < 0.05). There was no statistical difference in clinical sores between the diabetic and non-diabetic patients. In multivariate analysis associating age, gender and body mass index with pain and knee score at the latest follow-up, the average knee scores in normal and overweight group were found to be significantly higher than those in the obese group. The diabetic patients had an increased overall incidence of postoperative complications (17.6%) compared with the control group (8.1%) (p < 0.05). Particularly, the rate of wound complications such as skin necrosis, bulla formation or erythema with drainage was higher in the diabetic group (p < 0.05). Diabetes-related factors did not influence the incidence of complications. Associated diseases were the only significant risk factors correlated with wound complications and meniscal bearing dislodgement.

CONCLUSION

Patients with diabetes can benefit from TKA, even though diabetic patients are at an increased risk for overall postoperative and wound complications. Preoperative factors such as obesity and associated diseases may adversely affect the clinical outcome of TKA in diabetic patients.