Marcella Malavolti

Cross-calibration of eight-polar bioelectrical impedance analysis versus dual-energy X-ray absorptiometry for the assessment of total and appendicular body composition in healthy subjects aged 21-82 years.

Aim: To calibrate eight-polar bioelectrical impedance analysis (BIA) against dual-energy X-ray absorptiometry (DXA) for the assessment of total and appendicular body composition in healthy adults. Research design: A cross-sectional study was carried out. Subjects: Sixty-eight females and 42 males aged 21-82 years participated in the study. Methods: Whole-body fat-free mass (FFM) and appendicular lean tissue mass (LTM) were measured by DXA; resistance ( R ) of arms, trunk and legs was measured by eight-polar BIA at frequencies of 5, 50, 250 and 500 kHz; whole-body resistance was calculated as the sum R of arms, trunk and legs. Results: The resistance index (RI), i.e. the height 2 /resistance ratio, was the best predictor of FFM and appendicular LTM. As compared with weight (Wt), RI at 500 kHz explained 35% more variance of FFM ( vs 0.57), 45% more variance of LTM arm ( vs 0.48) and 36% more variance of LTM leg ( vs 0.50) ( p < 0.0001 for all). The contribution of age to the unexplained variance of FFM and appendicular LTM was nil or negligible and the RI 2 sex interactions were either not significant or not important on practical grounds. The percent root mean square error of the estimate was 6% for FFM and 8% for LTM arm and LTM leg. Conclusion: Eight-polar BIA offers accurate estimates of total and appendicular body composition. The attractive hypothesis that eight-polar BIA is influenced minimally by age and sex should be tested on larger samples including younger individuals.

Accuracy of an eight-point tactile-electrode impedance method in the assessment of total body water.

Objective: To establish the accuracy of an eight-polar tactile-electrode impedance method in the assessment of total body water (TBW).Design: Transversal study.Setting: University department.Subjects: Fifty healthy subjects (25 men and 25 women) with a mean (s.d.) age of 40 (12) y.Methods: TBW measured by deuterium oxide dilution; resistance (R) of arms, trunk and legs measured at frequencies of 5, 50, 250 and 500 kHz with an eight-polar tactile-electrode impedance-meter (InBody 3.0, Biospace, Seoul, Korea).Results: An algorithm for the prediction of TBW from the whole-body resistance index at 500 kHz (height 2/R500 where R is the sum of the segmental resistances of arms, trunk and legs) was developed in a randomly chosen subsample of 35 subjects. This algorithm had an adjusted coefficient of determination (r2adj) of 0.81 (P<0.0001) and a root mean square error (RMSE) of 3.6 l (9%). Cross-validation of the predictive algorithm in the remaining 15 subjects gave an r2adj of 0.87 (P<0.0001) and an RMSE of 3.0 l (8%). The precision of eight-polar BIA, determined by measuring R three times a day for five consecutive days in a fasting subject, was ≤2.8% for all segments and frequencies.Conclusion: Eight-polar BIA is a precise method that offers accurate estimates of TBW in healthy subjects. This promising method should undergo further studies of precision and its accuracy in assessing extracellular water and appendicular body composition should be determined.Sponsorship: Modena and Reggio Emilia University.

Sensitivity and specificity of body mass index and skinfold thicknesses in detecting excess adiposity in children aged 8-12 years.

Primary objective : The study aimed to evaluate the sensitivity (SN) and specificity (SP) of body mass index (BMI) and skinfold thicknesses in detecting excess adiposity in children. Research design : Cross-sectional. Materials and methods : 986 children (500 females and 486 males) aged 10 - 1 years (mean - SD; range: 8-12 years) were studied. All underwent anthropometric measurements and bioelectrical impedance analysis (BIA). Dual-energy X-ray absorptiometry (DXA) was performed in 52 children to develop a population-specific algorithm for the assessment of fat-free mass (FFM) from BIA. The algorithm was applied to the remaining 934 children to estimate their FFM. Fat mass (FM) was obtained by subtracting FFM from weight (Wt). Values of FM:Wt were transformed in Z -scores and converted into 19 percentile categories (from 5 to 95 in steps of 5). The same procedure was performed with BMI and the log-transformed sum of four skinfold thicknesses (triceps, biceps, subscapular and suprailiac; lt-4SF). Excess adiposity was defined as a level of FM:Wt greater than the internally derived 85th percentile. SN and SP of each internally derived percentile of BMI and lt-4SF in detecting excess adiposity were calculated. Results : In the pooled sample ( n = 934), SN and SP were 0.39 and 0.99 for the 95th percentile of BMI, 0.65 and 0.95 for the 85th percentile of BMI, and 0.75 and 0.94 for the 85th percentile of lt-4SF. Conclusions : BMI percentiles employed in the present study have a high SP but a low SN in detecting excess adiposity in 8-12-year-old children. The use of the sum of four skinfolds has the potential to increase the SN of a screening programme for excess adiposity in children of this age.

Accuracy of eight-polar bioelectrical impedance analysis for the assessment of total and appendicular body composition in peritoneal dialysis patients

Objective:To establish the accuracy of bioelectrical impedance analysis (BIA) for the assessment of total and appendicular body composition in peritoneal dialysis (PD) patients.Design:Cross-sectional study.Setting:University Nephrology Clinic.Subjects:In all, 20 PD patients and 77 healthy controls matched for gender, age and body mass index.Methods:Whole-body fat-free mass (FFM) and appendicular lean tissue mass (LTM) were measured by dual-energy X-ray absorptiometry. Resistance (R) of arms, trunk and legs was measured by eight-polar BIA at frequencies of 5, 50, 250 and 500 kHz. Whole-body resistance was calculated as the sum of R of arms, trunk and legs. The resistance index (RI) was calculated as the ratio between squared height and whole-body or segmental R.Results:RI at 500 kHz was the best predictor of FFM, LTMarm and LTMleg in both PD patients and controls. Equations developed on controls overestimated FFM and LTMarm and underestimated LTMleg when applied to PD patients. Specific equations were thus developed for PD patients. Using these equations, the percent root mean-squared errors of the estimate for PD patients vs controls were 5 vs 6% for FFM, 8 vs 8% for LTMarm and 7 vs 8% for LTMleg.Conclusion:Eight-polar BIA offers accurate estimates of total and appendicular body composition in PD patients, provided that population-specific equations are used.Sponsorship:University of Modena and Reggio Emilia.

Selenium speciation in human serum and its implications for epidemiologic research: a cross-sectional study

Observational studies addressing the relation between selenium and human health, particularly cancer risk, yielded inconsistent results, while most recent randomized trials showed a fairly consistent pattern suggesting null or adverse effects of the metalloid. One of the most plausible explanations for such inconsistencies is inadequate exposure assessment in observational studies, commonly carried out by measuring total Se content without taking into account the specific exposure to the individual chemical forms of the metalloid, whose toxic and nutritional properties may vary greatly. Data on the distribution of these species in human blood and their correlation with overall selenium levels are very limited. The concentrations of organic and inorganic selenium species were analyzed in serum of fifty subjects sampled from the general population of the municipality of Modena, northern Italy, aged from 35 to 70 years. Samples were collected during a 30-month period, and determinations of selenium species were carried out using high pressure liquid chromatography coupled with inductively coupled plasma dynamic reaction cell mass spectrometry. The majority of selenium was found to be present as organic species, but the inorganic forms showed higher levels than expected. These species showed limited correlations with age, sex and body mass index, while the organic forms increased in subjects consuming selenium-containing dietary supplements and decreased in smokers. The length of the sample storage period strongly influenced the distribution of selenium compounds, with a clear tendency towards higher inorganic and lower organic selenium levels over time. In multivariate analysis adjusting for potential confounders, total serum selenium correlated with human serum albumin-bound selenium and, in males, with two organic species of the metalloid (selenocysteine and glutathione peroxidase-bound selenium), while little association existed with the other organic forms and the inorganic ones. These findings highlight the potential for exposure misclassification of observational epidemiologic investigations based on overall selenium content in blood and possibly other tissues, and the critical role of the storage conditions for speciation analysis.

Relationship between body composition and bone mineral content in young and elderly women.

Primary objective : To study the relationship between bone mineral content (BMC), lean tissue mass (LTM) and fat mass (FM) in a large sample of young and elderly women. Research design : Cross-sectional. Methods and procedures : BMC, LTM and FM were measured by dual-energy X-ray absorptiometry in 2009 free-dwelling Caucasian women aged 63 - 7 years (mean - SD; range: 37-88 years). The majority of women were postmenopausal (96%). Results : LTM explained 13% more variance of BMC than FM ( R 2 adj = 0.39 vs 0.26, p < 0.0001) but weight (Wt) explained 5% more variance of BMC than LTM ( R 2 adj = 0.44, p < 0.0001). The prediction of BMC obtained from LTM and FM ( R 2 adj = 0.46, p < 0.0001) was only slightly better than that obtained from Wt. After the effects of age, Wt and height (Ht) on BMC were taken into account by multiple regression, the contribution of LTM and FM to BMC was just one-fifth of that of Wt ( R 2 adj for full models r 0.56, p < 0.0001). After a further correction for bone area (BA), the contribution of LTM and FM to BMC was just one-tenth of that of BA and not different from that of Wt and Ht on practical grounds ( R 2 adj for full models = 0.84, p < 0.0001). Thus, after inter-individual differences in age, Wt, Ht (and bone size) are taken into account, the relationship between body composition and BMC is substantially weakened. Conclusions : In Caucasian women, (1) LTM is a stronger predictor of BMC than FM, but (2) Wt is a better predictor of BMC than body composition for practical purposes, and (3) Wt and body composition are not able to explain more than 46% of BMC variance.

Short-term multidisciplinary non-pharmacological intervention is effective in reducing liver fat content assessed non-invasively in patients with nonalcoholic fatty liver disease (NAFLD)

BACKGROUND Non-alcoholic fatty liver disease (NAFLD) ranges from simple steatosis to steatohepatitis, and cirrhosis in patients with alcohol intake less than 20 g/day, and is usually associated with insulin resistance (IR). AIM Given that no drugs are specifically approved for NAFLD, we tested the efficacy of a non-pharmacological multidisciplinary intervention based on a personalized diet, physical activity and behavior therapy. METHODS In this open non-randomized study, personalized diet, physical exercise and behaviour therapy for 3 months were prescribed in 12 consecutive patients with NAFLD. Lifestyle, including total caloric intake, physical activity and resting energy expenditure was monitored by a SenseWear Armband. Insulin Resistance (IR) was measured by HOMA and oral glucose insulin sensitivity tests (OGIS); fat liver content was estimated by two different semi-quantitative scores and by the Doppler Power Index (DPI). RESULTS Data show that the multidisciplinary intervention produced a significant reduction of total caloric intake, a 8% reduction in body weight, a modest increase in daily physical activity, a significant (P<0.001) reduction of aminotransferases and a decrease of total hepatic fat content. CONCLUSIONS A 3-month multidisciplinary intervention inducing at least 8% of weight loss, improves liver tests and decreases liver fat content.

Metabolic syndrome: A child is not a small adult

Obesity is associated with an increased all-cause mortality rate and even small weight losses can be associated with short-term reduction in risk factors for disease. There is strong evidence that weight loss in obese subjects improves risk factors for diabetes and cardiaovascular diseases. Metabolic syndrome (MS) in adults is defined as a cluster of risk factors for cardiovascular disease and type 2 diabetes mellitus, which includes abdominal obesity, dyslipidemia, glucose intolerance and hypertension. Application of the MS concept in children and adolescents is controversial; in fact no consensus exists on a specific definition for pediatric MS. Lack of consensus is in part due to body evolution associated with childhood and puberty that is related to changes in metabolic and clinical characteristics. The aim of this article is to try to clarify the differences between the MS as a concept and the MS as a diagnostic category, as well as to develop a theory related to its pathophysiology. We comment on the relationship between obesity, regional fat distribution and the MS, and finally we offer some insights into MS methodological approaches for estimating metabolic risk-factor clustering in children and adolescents.

Physical activity for the prevention and treatment of metabolic disorders

Metabolic syndrome and its various features (obesity, hypertension, dyslipidemia, diabetes, and nonalcoholic fatty liver disease) are increasing worldwide and constitute a severe risk for the sustainability of the present universal Italian health care system. Lifestyle interventions should be the first therapeutic strategy to prevent/treat metabolic diseases, far before pharmacologic treatment. The role of diet and weight loss has been fully ascertained, whereas the role of physical activity is frequently overlooked both by physicians and by patients. Physical activity has favorable effects on all components of the metabolic syndrome and on the resulting cardiovascular risk, the cornerstone in the development of cardiometabolic diseases. The quantity and the frequency of physical activity necessary to produce beneficial effects has not been defined as yet, but brisk walking is considered particularly appropriate, as it can be practiced by a large number of individuals, without any additional cost, and has a low rate of injury. The effects of exercise and leisure time physical activity extend from prevention to treatment of the various components of the metabolic syndrome, as well as to mood and quality of life. Any effort should be done to favor adherence to protocols of physical activity in the community.

Toenail selenium and risk of type 2 diabetes: the ORDET cohort study

Epidemiologic studies, particularly randomized controlled trials, have shown a direct relation between dietary and environmental exposure to the metalloid selenium and risk of type 2 diabetes. We investigated the association between baseline toenail selenium levels and diabetes occurrence in a case-control study nested in ORDET, a population-based female cohort in Northern Italy. After a median follow-up of 16 years, we identified 226 cases of type 2 diabetes cases and 395 age-matched control women with available toenail samples at baseline. The multivariate odds ratios of diabetes in increasing a priori defined categories of toenail selenium exposure were 1.09 (95% confidence interval 0.61, 1.96), 0.71 (0.38, 1.34) and 1.14 (0.46, 2.80) compared with the lowest category. The results were not substantially altered when quartile distribution of toenail selenium in controls was used to define exposure categories. Spline regression analysis did not show homogeneous risk trends. Overall, we did not find an association between toenail selenium and subsequent development of diabetes. Since the diabetogenic activity of selenium is strongly supported by experimental studies and some observational investigations, our null results might be explained by the limitations of overall selenium toenail content to assess environmental exposure to selenium species of etiologic relevance in the study population.