Functional body composition: insights into the regulation of energy metabolism and some clinical applications

Advances in body composition: a 100-year journey

Knowledge of human body composition at the dawn of the twentieth century was based largely on cadaver studies and chemical analyses of isolated organs and tissues. Matters soon changed by the nineteen twenties when the Czech anthropologist Jindřich Matiegka introduced an influential new anthropometric method of fractionating body mass into subcutaneous adipose tissue and other major body components. Today, one century later, investigators can not only quantify every major body component in vivo at the atomic, molecular, cellular, tissue-organ, and whole-body organizational levels, but go far beyond to organ and tissue-specific composition and metabolite estimates. These advances are leading to an improved understanding of adiposity structure-function relations, discovery of new obesity phenotypes, and a mechanistic basis of some weight-related pathophysiological processes and adverse clinical outcomes. What factors over the past one hundred years combined to generate these profound new body composition measurement capabilities in living humans? This perspective tracks the origins of these scientific innovations with the aim of providing insights on current methodology gaps and future research needs.

Energy Expenditure in Upper Gastrointestinal Cancers: a Scoping Review

Malnutrition is prevalent in people with upper gastrointestinal (GI) cancers and is associated with shorter survival and poor quality of life. In order to effectively prevent or treat malnutrition, nutrition interventions must ensure appropriate energy provision to meet daily metabolic demands. In practice, the energy needs of people with cancer are frequently estimated from predictive equations which are not cancer-specific and are demonstrated to be inaccurate in this population. The purpose of this scoping review was to synthesize the existing evidence regarding energy expenditure in people with upper GI cancer. Three databases (Ovid MEDLINE, Embase via Ovid, CINAHL plus) were systematically searched to identify studies reporting on resting energy expenditure using indirect calorimetry and total energy expenditure using doubly labeled water (DLW) in adults with any stage of upper GI cancer at any point from diagnosis. A total of 57 original research studies involving 2,125 individuals with cancer of the esophagus, stomach, pancreas, biliary tract, or liver were eligible for inclusion. All studies used indirect calorimetry, and one study used DLW to measure energy expenditure, which was reported unadjusted in 42 studies, adjusted for body weight in 32 studies, and adjusted for fat-free mass in 13 studies. Energy expenditure in upper GI cancer was compared with noncancer controls in 19 studies and measured compared with predicted energy expenditure reported in 31 studies. There was heterogeneity in study design and in reporting of important clinical characteristics between studies. There was also substantial variation in energy expenditure between studies and within and between cancer types. Given this heterogeneity and known inaccuracies of predictive equations in patients with cancer, energy expenditure should be measured in practice wherever feasible. Additional research in cohorts defined by cancer type, stage, and treatment is needed to further characterize energy expenditure in upper GI cancer.

Fat and lean mass predict time to hospital readmission or mortality in children treated for complicated severe acute malnutrition in Zimbabwe and Zambia

HIV and severe wasting are associated with post-discharge mortality and hospital readmission among children with complicated severe acute malnutrition (SAM); however, the reasons remain unclear. We assessed body composition at hospital discharge, stratified by HIV and oedema status, in a cohort of children with complicated SAM in three hospitals in Zambia and Zimbabwe. We measured skinfold thicknesses and bioelectrical impedance analysis (BIA) to investigate whether fat and lean mass were independent predictors of time to death or readmission. Cox proportional hazards models were used to estimate the association between death/readmission and discharge body composition. Mixed effects models were fitted to compare longitudinal changes in body composition over 1 year. At discharge, 284 and 546 children had complete BIA and skinfold measurements, respectively. Low discharge lean and peripheral fat mass were independently associated with death/hospital readmission. Each unit Z-score increase in impedance index and triceps skinfolds was associated with 48 % (adjusted hazard ratio 0·52, 95 % CI (0·30, 0·90)) and 17 % (adjusted hazard ratio 0·83, 95 % CI (0·71, 0·96)) lower hazard of death/readmission, respectively. HIV-positive v. HIV-negative children had lower gains in sum of skinfolds (mean difference -1·49, 95 % CI (-2·01, -0·97)) and impedance index Z-scores (-0·13, 95 % CI (-0·24, -0·01)) over 52 weeks. Children with non-oedematous v. oedematous SAM had lower mean changes in the sum of skinfolds (-1·47, 95 % CI (-1·97, -0·97)) and impedance index Z-scores (-0·23, 95 % CI (-0·36, -0·09)). Risk stratification to identify children at risk for mortality or readmission, and interventions to increase lean and peripheral fat mass, should be considered in the post-discharge care of these children.

Fat-to-lean mass ratio as a new anthropometric indicator in predicting metabolic syndrome among Malay adolescents in Terengganu, Malaysia

Background

Metabolic syndrome (MetS) is defined as a cluster of risk factors for predicting type 2 diabetes mellitus and cardiovascular disease.

Objectives

This cross-sectional study aimed to develop a cut-off value for fat versus lean mass ratio (FLMR) in predicting MetS and to investigate the association between this indicator with MetS and its components.

Methods

Subjects comprised 238 Malay adolescents (79% female) aged 18–19 years old. Anthropometric assessment comprised weight, height and waist circumference (WC). Body composition was measured using bioelectrical impedance analysis techniques while blood pressure was measured using a blood pressure monitor. Fasting blood glucose, total cholesterol , triglycerides, high-density lipoprotein cholesterol (HDL-c), and low-density lipoprotein cholesterol were determined from an overnight fasting blood sample. MetS was determined based on International Diabetes Federation (2007) definition for adolescents aged 16-year-old and above.

Results

The prevalence of MetS was 2.1%. Receiver Operating Characteristics curve analysis revealed that the optimal cut-off value for FLMR was 0.441 with an Area Under the Curve of 0.874 (95% CI: 0.825, 0.913); with sensitivity of 80.0% and specificity of 71.0%. FLMR cut-off of 0.441 was associated with high WC ( p < .001), low HDL-c ( p < .001) and MetS ( p < .05). Binary Logistic Regression analysis revealed that adolescents with high WC, low HDL-c and MetS had higher odds of developing increased FLMR than the cut-off value with an odds ratio (OR) of 43.4 (95% CI: 9.7,193.9), 4.7 (95% CI: 2.3,9.8) and 13.3 (95% CI: 1.5,121.2), respectively.

Conclusion

FLMR possesses fair discriminatory ability in identifying MetS among adolescents and significant association exists between FLMR and MetS and some of its components.

Age-Related Trends in Body Composition among Women Aged 20-80 Years: A Cross-Sectional Study

The determinants of body composition are likely to vary geographically due to the diversity of genetic and environmental factors between populations. Age-related trends in body composition in a population help understanding the health issues that are linked with different body compartments. In general, such studies are scarce in the South Asian region and this cross-sectional study examined the age-related trends in body composition in a selected group of healthy women aged 20-80 years in Sri Lanka. The study included randomly selected 784 healthy women aged 20-80 years from the Southern province, Sri Lanka. Women were divided into five age groups: 20-29 years (n = 79), 30-39 years (n = 144), 40-49 years (n = 185), 50-59 years (n = 281), and ≥60 years (n = 85). Total body bone mineral density (TBBMD, g/cm²), total body bone mineral content (TBBMC, g), total body fat mass (TBFM, kg), and total body lean mass (TBLM, kg) were measured with central-type dual-energy X-ray absorptiometry (DXA). Multivariate analysis of variance with Bonferroni post hoc test was performed. The age-related trends of TBBMD and TBBMC were similar with a peak in 40-49-year age group. Between 50 and 59 and ≥60 age categories, TBBMD and TBBMC showed a rapid decline: 16% and 23%, respectively. The rate of TBBMD decline was 0.008 g/cm² per year after 50 years. TBFM increased by 14% between age categories 20-29 and 40-49 years and remained unchanged after 49 years. TBLM increased by 15% between age groups 20-29 and 40-49 years and then decreased by 13% between age categories 50-59 and ≥60 years. Of the 13% decrease in TBLM after 50 years, 9% loss occurred after 59 years. The trends observed help to understand the occurrence of diseases linked with body composition.

Association Between Adipose Tissue Proton Density Fat Fraction, Resting Metabolic Rate and FTO Genotype in Humans

BACKGROUND

The difference of proton density fat fraction (PDFF) between supraclavicular and gluteal adipose tissue might indicate the presence of brown adipose tissue (BAT). Aim of this cross-sectional study was to investigate the association between PDFF over the supraclavicular fat region as a proxy of BAT proportion and resting metabolic rate (RMR). In addition, the association between the single nucleotide polymorphism (SNP) rs1421085 at the fat mass and obesity associated (FTO) gene locus and both PDFF and RMR was investigated.

METHODS

Anthropometric, clinical, and lifestyle data from 92 healthy adults (66.3% females, mean age: 36.2 ± 13.0 years, mean body mass index: 24.9 ± 5.4 kg/m²) were included in the analysis. The RMR was measured by indirect calorimetry. The magnetic resonance imaging (MRI) was used for the measurement of visceral and subcutaneous adipose tissue (VAT, SAT) volumes and for the measurement of adipose tissue PDFF.

RESULTS

Mean RMR of the whole group was 1 474.8 ± 242.2 kcal. Genotype data was available for 90 participants. After adjustment for age, sex, weight change and fat-free mass (FFM), no association was found between supraclavicular PDFF (p = 0.346) and gluteal PDFF (p = 0.252), respectively, and RMR, whereas statistically significant evidence for a negative association between delta PDFF (difference between gluteal PDFF and supraclavicular PDFF) and RMR (p = 0.027) was obtained. No statistically significant evidence was observed for per FTO risk allele change in RMR, gluteal and supraclavicular PDFF maps or volumes of VAT and SAT.

CONCLUSIONS

Supraclavicular PDFF as a surrogate marker of BAT presence is not a determinant of RMR under basal conditions. In the present study, the FTO rs1421085 variant is not associated with either RMR or PDFF. Further studies are needed to elucidate the effect of BAT on RMR.

Metabolic flexibility differs by body composition in adults

BACKGROUND & AIMS

With the rise of global cardiometabolic diseases, it is important to investigate risk factors such as obesity. Metabolic flexibility, the ability to maintain metabolic homeostasis following an acute challenge, can reflect cardiometabolic health. We investigated the association between body composition and the metabolic flexibility following meal consumption in an adult population.

METHODS

In this study of 1027 participants (mean age 44.0 y ± SD 4.2 y), we administered a mixed-macronutrient meal challenge. Fasting and 2-h postprandial plasma were assayed for lipids, glycemic, and inflammation biomarkers. We characterized metabolic flexibility through meal-induced biomarker responses (%Δ, the difference between postprandial and fasting concentrations, divided by fasting concentration). We then compared the responses by sex-specific tertiles of body mass index (BMI) and percent body fat.

RESULTS

With every unit (kg/m²) increase in BMI, %Δ (95% confidence interval) increased by 0.17% (0.09, 0.26%) for total cholesterol, 0.31% (0.07, 0.54%) for triglycerides, and 0.11% (0.01, 0.20%) for apoA-I, whereas insulin elevation was reduced (-6.30%; -8.41, -4.20%), and the reduction in leptin was attenuated (0.64%; 0.25, 1.05%). With each unit (percent) increase in body fat, we observed similar changes in the %Δ of total cholesterol and leptin but not in triglycerides, apoA-I, or insulin. Glucose response increased by 0.29% (0.06, 0.51%) as body fat increases by one unit.

CONCLUSION

Metabolic flexibility, as assessed by biomarker responses to an acute physiological meal challenge, differed by body composition. These findings may help elucidate the pathways through which obesity contributes to cardiometabolic diseases.

Is constitutional thinness really different from anorexia nervosa? A systematic review and meta-analysis

A growing interest in constitutional thinness has been observed in the last decades, but the publications however cover various fields of study and report equivocal results. The present work systematically reviewed any clinical trials enrolling participants with constitutional thinness and bibliographic researches were performed between December 2018 and June 2020. From a total of 1 212 records initially identified, 402 records were removed as duplicates, 381 articles were excluded based on titles or abstracts and 390 references were excluded against eligibility criteria. Thirty-nine articles were finally included in the systematic review. The results showed that constitutionally thin people seem to be underweight but not underfat and present a fat-free mass as blunted as anorexic patients, despite being a little less underweight. The meta-analysis confirmed that constitutionally thin people present normal energy intake and revealed a trend toward a higher resting metabolic rate to fat-free mass ratio which suggests a highly metabolic fat-free mass. Contrary to patients with anorexia nervosa, constitutionally thin people present normal levels of insulin-like growth factor 1, estradiol, growth hormone, follicle-stimulating hormone, and luteinizing hormone. An intermediate level of leptin between anorexic and control participants was however observed in constitutional thinness. While all the studies reported normal free triiodothyronine and cortisol levels in constitutionally thin individuals, a higher fasting free triiodothyronine level (p = 0.033) and a lower 24 h mean cortisol level (p = 0.005) were observed for the first time. Present results give robust evidence that constitutionally thin people present an atypical phenotype highly different from anorexia nervosa.

Underweight but not underfat: is fat-free mass a key factor in constitutionally thin women?

Constitutional thinness is defined as a state of severe underweight with a body mass index similar to anorectic patients (BMI < 17.5 kg/m²), in the absence of any eating disorders or other obvious disruptive factors impacting energy balance. The analysis of body composition is essential as a first approach to characterize constitutional thinness and might help identify new discriminating differences between constitutional thinness and anorexia nervosa. A meta-analytical approach was performed to compare body composition of constitutionally thin, anorectic, and normal-weight subjects from all available studies found in the literature. The statistical analysis was carried out on large sample sizes: n = 205 females with constitutional thinness, n = 228 normal-weight control females, and n = 258 females with anorexia nervosa. Despite being as underweight as anorectic patients, constitutionally thin participants paradoxically presented higher percentages of fat mass than anorectic patients (18.9% vs. 11.4%, respectively; SMD [95% CI]: 1.62 [1.16; 2.08]), even found in the normal healthy ranges. Constitutionally thin people, however, display as low fat-free mass as anorectic patients. These observations question the use of high-fat diets in this population and bring new insights for nutrition and/or training strategies directed toward muscle mass gain. The present results give new elements to further distinguish constitutional thinness from anorexia nervosa and reinforce the need to better investigate the atypical phenotype of constitutional thinness.

Energy Metabolism in Relation to Diet and Physical Activity: A South Asian Perspective

The prevalence of overweight and obesity is on the rise around the world, not only in the West, but also in Asian countries. South Asian countries in particular are experiencing a rapid increase in overweight and obesity, that coexists with the rapid increase in non-communicable diseases linked to obesity such as diabetes and cardiovascular disease than any other country in Asia. The phenomena observed in South Asian countries are due to the size of the population, the ageing of the population, the high degree of urbanization and the lifestyle changes in favor of increased energy consumption and reduced physical activity. The imbalance between energy consumption and energy expenditure results in the development of a positive energy balance that, over time, accumulates in higher body fat. South Asians were reported to have a more unfavorable body composition with a higher percentage of body fat than Caucasians with an equivalent BMI. Body composition is a major determinant of resting energy expenditure. It has been reported that South Asians have a lower resting energy expenditure than Caucasians with the same BMI. Resting energy expenditure accounts for the majority of total daily energy expenditure and, therefore, plays a crucial role in achieving the balance between energy intake and expenditure.

Artificial intelligence and abdominal adipose tissue analysis: a literature review

Body composition imaging relies on assessment of tissues composition and distribution. Quantitative data provided by body composition imaging analysis have been linked to pathogenesis, risk, and clinical outcomes of a wide spectrum of diseases, including cardiovascular and oncologic. Manual segmentation of imaging data allows to obtain information on abdominal adipose tissue; however, this procedure can be cumbersome and time-consuming. On the other hand, quantitative imaging analysis based on artificial intelligence (AI) has been proposed as a fast and reliable automatic technique for segmentation of abdominal adipose tissue compartments, possibly improving the current standard of care. AI holds the potential to extract quantitative data from computed tomography (CT) and magnetic resonance (MR) images, which in most of the cases are acquired for other purposes. This information is of great importance for physicians dealing with a wide spectrum of diseases, including cardiovascular and oncologic, for the assessment of risk, pathogenesis, clinical outcomes, response to treatments, and complications. In this review we summarize the available evidence on AI algorithms aimed to the segmentation of visceral and subcutaneous adipose tissue compartments on CT and MR images.

Resting Energy Expenditure and Related Factors in 6- to 9-Year-Old Southern African Children of Diverse Population Groups

Lower resting energy expenditure (REE) may partially explain the disproportionate prevalence of overweight/obesity among black African women. As no previous studies have investigated the REE of Southern African (South. Afr.) children, we aimed to determine, by sex and population group, the REE of 6- to 9-year-old urban school children. In a cross-sectional study with quota sampling, REE was measured with indirect calorimetry (IC). Confounders considered were: body composition (BC) (fat-free mass (FFM), FFM index, fat mass (FM), FM index), assessed using multifrequency bioelectrical impedance analysis, and physical activity (PA) measured with a pedometer. Multivariate regression was used to calculate REE adjusted for phenotypes (BC, z-scores of weight-for-age, height-for-age, body mass index-for-age) and PA. Sex and population differences in REE were determined with two-way ANOVA. Ninety-four healthy children (59.6% girls; 52.1% black) with similar socioeconomic status and PA opportunities participated. Despite BC variations, sex differences in REE were not significant (41 kcal/day; P = 0.375). The REE of black participants was lower than of white (146 kcal/day; P = 0.002). When adjusted for FFM and HFA z-score, the differences in REE declined but remained clinically meaningful at 91 kcal/day (P = 0.039) and 82 kcal/day (P = 0.108), respectively. We recommend the development of population-specific REE prediction equations for South. Afr. children.

Effects of Exercise on Resting Metabolic Rate in Adolescents with Overweight and Obesity

Background: We examined the effects of exercise training on resting metabolic rate (RMR), and whether changes in body composition are associated with changes in RMR in adolescents with overweight and obesity. Methods: One hundred forty adolescents (12-18 years, BMI ≥85th percentile) participated in randomized exercise trials (3-6 months) at UPMC Children's Hospital of Pittsburgh (18 control, 51 aerobic, 50 resistance, and 21 combined aerobic and resistance exercise). All participants had RMR assessments by indirect calorimetry after a 10-12 hour overnight fast, and body composition by magnetic resonance imaging and dual-energy X-ray absorptiometry. Results: There were no significant changes in RMR (kcal/day) between exercise groups vs. controls (p > 0.05). All exercise groups decreased visceral fat (-0.2 ± 0.02 kg; p < 0.05) compared to control. Increases in fat-free mass (FFM) were only seen in the combined group (2.3 ± 0.4 kg; p < 0.05), whereas increases in skeletal muscle mass were observed in both resistance (1.2 ± 0.2 kg; p < 0.05) and combined (1.5 ± 0.3 kg; p < 0.05) groups vs. control. Change in FFM, but not fat mass (FM), visceral fat, or skeletal muscle mass (p > 0.05), was a significant determinant of changes in RMR, independent of exercise modality (p = 0.04). Conclusion: Although exercise modality was not associated with changes in RMR, change in FFM, but not skeletal muscle or FM, was a significant correlate of changes in RMR in adolescents with overweight and obesity. Clinicaltrials.gov registration numbers: NCT00739180, NCT01323088, NCT01938950.

The Fat-to-Lean Mass Ratio Is Associated with Hyperinsulinemia in Healthy Mexican Adolescents

Objective: To evaluate whether the Fat-to-Lean Mass (FyM) ratio is associated to hyperinsulinemia in healthy adolescents.Methods: Apparently healthy adolescents aged 10 to 15 years that according to sex, age, and percentiles of body fat percent, were included and allocated into the groups with elevated (body fat percent ≥85 percentile) and normal total body fat (body fat percent <85 percentile). The FyM ratio was calculated as total lean mass (kg)/total body fat (kg) and hyperinsulinemia was defined by fasting insulin levels ≥20 µUI/mL.Results: A total of 1,299 adolescents, 665 (51.9%) girls and 634 (48.1%) boys, were enrolled and allocated into the groups with high (n = 439) and normal (n = 860) body fat. The FyM index remained significantly associated with hyperinsulinemia (OR 5.58; _95%CI: 1.54-28.10) after logistic regression analysis adjusted by sex, age, body-weight, body mass index, and waist circumference.Conclusion: The FyM index is highly associated to the presence of hyperinsulinemia in adolescents, emerging as a useful tool from anthropometric measurements for identify insulin abnormalities.

The effects of chemotherapy on energy metabolic aspects in cancer patients: A systematic review

BACKGROUND & AIMS

Cancer survival rates have increased significantly creating more awareness for comorbidities affecting the Quality of Life. Chemotherapy may induce serious metabolic alterations. These complications can create an energy imbalance, worsening prognosis. The effect of chemotherapy on energy metabolism remains largely unknown. The purpose of this systematic review is to determine the impact of chemotherapy on energy metabolism, creating more insight in a patients' energy requirements.

METHODS

We identified relevant studies up to May 2nd, 2019 using PubMed and Web of Science. Studies including all types of cancer and stages were selected. Only patients that underwent chemotherapy whether or not followed by surgery or radiotherapy were selected. Maximum follow-up was set at 6 months. Resting energy expenditure (REE), measured by indirect calorimetry (IC) or predicted by the Harris-Benedict equation (HB_Eq), was our primary outcome. Results regarding body composition were considered as secondary outcome parameter.

RESULTS

16 studies were selected, including 267 patients. Overall, a significant decrease in REE [-1.5% to -24.91%] 1-month post-chemotherapy was reported. Two studies on breast cancer conducted a 3 and 6-month follow-up and found an increase in REE of 4.01% and 5.72% (p < .05), revealing a U-shaped curve in the expression of REE. Changes are accompanied by (non)significant variations in body composition (Fatmass (FM) and Fatfree Mass (FFM)). HB_Eq tends to underestimate REE by 4.03%-27.1%.

CONCLUSION

Alterations in REE, accompanied by changes in body composition, are found during and after chemotherapy in all cancer types and stages, revealing a U-shaped curve. Changes in FFM are suggested to induce variations in REE concomitant to catabolic effects of the disease and administered drug. HB_Eq tends to underestimate REE, stressing the need for adequate assessment to meet patients' energy requirements and support dietary needs.

Deep Multi-OMICs and Multi-Tissue Characterization in a Pre- and Postprandial State in Human Volunteers: The GEMM Family Study Research Design

Cardiovascular disease (CVD) and type 2 diabetes (T2D) are increasing worldwide. This is mainly due to an unhealthy nutrition, implying that variation in CVD risk may be due to variation in the capacity to manage a nutritional load. We examined the genomic basis of postprandial metabolism. Our main purpose was to introduce the GEMM Family Study (Genetics of Metabolic Diseases in Mexico) as a multi-center study carrying out an ongoing recruitment of healthy urban adults. Each participant received a mixed meal challenge and provided a 5-hours’ time course series of blood, buffy coat specimens for DNA isolation, and adipose tissue (ADT)/skeletal muscle (SKM) biopsies at fasting and 3 h after the meal. A comprehensive profiling, including metabolomic signatures in blood and transcriptomic and proteomic profiling in SKM and ADT, was performed to describe tendencies for variation in postprandial response. Our data generation methods showed preliminary trends indicating that by characterizing the dynamic properties of biomarkers with metabolic activity and analyzing multi-OMICS data it could be possible, with this methodology and research design, to identify early trends for molecular biology systems and genes involved in the fasted and fed states.

Age- and sex-related differences in body composition in healthy subjects aged 18 to 82 years

Significant changes in body composition are known to occur with aging. The aim of the present study was to provide a normative reference of body composition and to investigate age and sex-related differences in healthy subjects by multifrequency bioelectrical impedance analyzer (BIA).A cross-sectional study was conducted on a sample of 3451 healthy Chinese adults, 1611 males and 1840 females. The volunteers were enrolled in 5 different age bands (18-30, 31-40, 41-50, 51-60, 60+). All subjects were measured for weight and height and submitted to BIA, to determine body composition. Body composition measures accounted for differences between men and women.A decrease in fat-free mass and increase in percent body fat was observed with aging, although the phenomenon was proved to be attenuated in women. The central and visceral redistribution of fat mass was also shown along lifetime.This study is a report on body composition of healthy subjects, to be used as an important data for future investigations and differences between nationalities and countries.

Functional correlates of detailed body composition in healthy elderly subjects

Methods of body composition analysis are now widely used to characterize health status, i.e., nutritional status, metabolic rates, and cardiometabolic risk factors. However, the functional correlates of individual body components have not been systematically analyzed. In this study, we have used a two-compartment model, which was assessed by air displacement plethysmography. Detailed body composition was measured by whole body magnetic resonance imaging in a healthy population of 40 Caucasians, aged 65–81 yr (20 men; body mass index range: 18.6–37.2 kg/m2). Physical, metabolic, as well as endocrine functions included pulmonary function, handgrip strength, gait speed, sit-to-stand test, physical activity, blood pressure, body temperature, resting energy expenditure (REE), liver and kidney functions (glomerular filtration rate), insulin sensitivity [homeostasis model assessment (HOMA)], plasma lipids, plasma leptin, testosterone, dehydroepiandrosterone, insulin-like growth factor I levels, thyroid status, vitamins, and inflammation. Individual body compartments were intercorrelated, e.g., skeletal muscle mass (SM) correlated with visceral adipose tissue ( r = 0.53) and kidneys ( r = 0.62). For the functional correlates, SM ( r = 0.58) and liver volume ( r = 0.63) were associated with REE, SM correlated with handgrip strength ( r = 0.57), and kidneys with glomerular filtration rate ( r = 0.57). While visceral adipose tissue correlated with HOMA ( r = 0.59), subcutaneous adipose tissue was related to plasma leptin levels ( r = 0.84). The subcutaneous adipose tissue-to-leptin relationship was moderated by inflammation increasing the explained variance of leptin levels by 4.0%. In linear regression analysis, detailed body composition explained variances in REE (75.0%), HOMA (41.0%), and leptin (78.0%) compared with a body mass index-based model (REE 16.0%, HOMA 31.0%, leptin 45.0%). In addition, detailed body composition explained 39.0% of the variance in kidney function.

NEW & NOTEWORTHY BCA should be used to address specific body functions only. In clinical practice, there is need of a clear focus on the specific research question related to physical, metabolic, or endocrine functions.

Forearm to fingertip skin temperature gradients in the thermoneutral zone were significantly related to resting metabolic rate: potential implications for nutrition research

BACKGROUND

Resting metabolic rate (RMR) should be measured in the thermoneutral zone (TNZ). Forearm to fingertip skin temperature gradients (FFG) could serve as an objective measure of this pre-condition.

SUBJECTS/METHODS

Eighty-six adult Australians were studied at 25 °C in a temperature-controlled chamber. Measurements of overnight fasted RMR, respiratory quotient (RQ) and FFG were complemented by clinical biochemistry. McAuley's Index of insulin sensitivity (McA_ISI) and presence of metabolic syndrome was determined. Physical activity was estimated from the short version of the International Physical Activity Questionnaire. Fat mass (FM) and fat-free mass (FFM) were obtained from dual-energy x-ray absorptiometry. Twenty-nine participants were assessed for changes in RMR (ΔRMR), RQ (ΔRQ) and FFG (ΔFFG) following a 6-month free-living period. Multiple linear regression analyses of RMR and RQ on FFG, and of ΔRMR and ΔRQ on ΔFFG were conducted after controlling for 12 known determinants of energy metabolism.

RESULTS

There were wide between-subject variations in unadjusted FFG ranging from -4.25 to +7.8 °C. The final parsimonious model for cross-sectional observations of RMR included age, FM, FFM, McA_ISI and FFG (β=63 kJ/d (95% confidence interval (CI): 14.2, 112.1, P=0.012)). However, FFG was unrelated to RQ.In the longitudinal cohort, adjusted ΔRMR significantly associated only with ΔFFG (β=100 kJ/d (95% CI: 10.3, 189.1; P=0.030)), and adjusted ΔRQ associated with ΔFFG (-0.003 (95% CI: -0.005, 0.0002, P=0.038)), age and McA_ISI.

CONCLUSIONS

Sizeable between-subject variations in FFG at 25 °C were associated with RMR and RQ. Monitoring FFG may serve as an objective assessment of the TNZ during RMR measurements.

Pilot Study to Explore the Accuracy of Current Prediction Equations in Assessing Energy Needs of Patients with Newly Diagnosed Glioblastoma Multiforme

Glioblastoma multiforme (GBM) is rare, yet it is the most common brain malignancy and has a poor prognosis. In regard to GBM, there is a dearth of research on resting energy expenditure (REE) and the accuracy of extant prediction equations. The aim of this cross-sectional study was to compare measured REE (mREE) to commonly used prediction equations in newly diagnosed GBM patients. REE was collected by indirect calorimetry in 20 GBM patients. Calculated REE was derived from Harris-Benedict (again with weight adjusted for obesity), Mifflin-St Jeor, and the 20 kcal/kg body weight ratio method. Paired t-tests and Bland-Altman analyses were used to compare group means, evaluate the bias, and find the limits of agreement. Clinical accuracy was assessed by determining the percentage of patients with predicted REE within ±10% of mREE. Subjects were evenly distributed with regard to gender, primarily Caucasian, and largely overweight or obese and had a mean age of 57 years. All equations overestimated mREE. Mifflin-St Jeor and adjusted Harris-Benedict had the narrowest limits of agreement and accurately predicted 60% and 65% of subjects, respectively. Clinicians should be aware of the discrepancy between commonly used prediction equations and REE. More research is needed to verify these findings and decipher the cause and significance in the GBM population.

Meal timing during alternate day fasting: Impact on body weight and cardiovascular disease risk in obese adults

OBJECTIVE

Alternate day fasting (ADF; 24-h feeding/24-h 25% energy intake at lunchtime), is effective for weight loss, but diet tolerability is questionable. Moving the fast day meal to dinnertime, or dividing it into smaller meals, may improve tolerability. Accordingly, this study compared the effects of ADF with three meal times on body weight and heart disease risk.

METHODS

Obese subjects (n = 74) were randomized to 1 of 3 groups for 8 weeks: 1) ADF-L: lunch, 2) ADF-D: dinner, or 3) ADF-SM: small meals.

RESULTS

Body weight decreased similarly (P < 0.001) in all groups (ADF-L: 3.5 ± 0.4 kg, ADF-D 4.1 ± 0.5 kg, ADF-SM 4.0 ± 0.5 kg). Reductions (P < 0.001) in fat mass and visceral fat were also comparable. Plasma lipids remained unchanged, and low density lipoprotein (LDL) particle size increased (P < 0.05) in all groups (1.3 ± 0.5 Å). Systolic blood pressure decreased (P < 0.05) by ADF-SM only. Fasting glucose, insulin, and HOMA-IR remained unchanged.

CONCLUSIONS

Thus, allowing individuals to consume the fast day meal at dinner or small meals produces similar weight loss and cardio-protection as consuming the meal at lunch. This flexibility in meal timing may increase tolerability and long-term adherence to ADF protocols.

Relationship between submaximal oxygen uptake, detailed body composition, and resting energy expenditure in overweight subjects

OBJECTIVE

We investigated the impact of detailed body composition on aerobic fitness to determine whether regional components of fat mass have independent effects on VO2submax , and whether VO2submax and detailed body composition independently explain variation in REE.

METHODS

71 healthy adults (80% female, 20% male, BMI 28.2-43.8 kg/m(2) ) were investigated. Body composition was measured by the four-compartment model together with whole body magnetic resonance imaging (MRI) to assess high and low metabolic rate organs and regional fat depots. VO2submax was estimated at 75% of predicted maximum heart rate.

RESULTS

There was a strong association between VO2submax and FFM and all organ masses except for heart. Skeletal muscle mass accounted for 34.8% of the variance in VO2submax . In addition, subcutaneous adipose tissue (SAT) of extremities explained additional 14.4%. FFM and FM explained 71.3% of the variance in REE. Including the components of FFM and FM, the explained variance in REE increased by about 5.8%; skeletal muscle mass explained 70.0% of the variance in REE and kidney and liver masses explained additional 7.1%. VO2submax correlated with REE. Taking into account body composition, VO2submax did not add to the variance in REE.

CONCLUSION

FFM is a determinant of both VO2submax and REE. Modeling either REE or VO2submax from individual components of FFM, about 77.1% of variance in REE (by muscle, liver and kidneys mass) and 34.8% of variance in VO2submax (by skeletal muscle mass) could be explained. FM explained additional variance in REE, whereas SAT of extremities added to the variance in VO2submax only.

Nutritional status evaluation in patients affected by bethlem myopathy and ullrich congenital muscular dystrophy

Collagen VI mutations lead to disabling myopathies like Bethlem myopathy (BM) and Ullrich congenital muscular dystrophy (UCMD). We have investigated the nutritional and metabolic status of one UCMD and seven BM patients (five female, three male, mean age 31 ± 9 years) in order to find a potential metabolic target for nutritional intervention. For this study, we used standard anthropometric tools, such as BMI evaluation and body circumference measurements. All results were compared to dual-energy X-ray absorptiometry (DXA), considered the “gold standard” method. Energy intake of each patient was evaluated through longitudinal methods (7-day food diary) while resting energy expenditure (REE) was predicted using specific equations and measured by indirect calorimetry. Clinical evaluation included general and nutritional blood and urine laboratory analyses and quantitative muscle strength measurement by hand-held dynamometry. BM and UCMD patients showed an altered body composition, characterized by low free fat mass (FFM) and high fat mass (FM), allowing us to classify them as sarcopenic, and all but one as sarcopenic-obese. Another main result was the negative correlation between REE/FFM ratio (basal energy expenditure per kilograms of fat-free mass) and the severity of the disease, as defined by the muscle megascore (correlation coefficient −0.955, P-value <0.001). We postulate that the increase of the REE/FFM ratio in relation to the severity of the disease may be due to an altered and pathophysiological loss of energetic efficiency at the expense of skeletal muscle. We show that a specific metabolic disequilibrium is related to the severity of the disease, which may represent a target for a nutritional intervention in these patients.

A comparison of fat and lean body mass index to BMI for the identification of metabolic syndrome in children and adolescents

CONTEXT

The use of body mass index (BMI) to assess risk for cardiometabolic disease in the pediatric population may be limited by a failure to differentiate between fat and lean body mass.

OBJECTIVES

The objectives of the study were to identify biologically based criteria for the definition of obesity using fat (FMI) and lean body mass index (LBMI) and to compare the ability of FMI and LBMI to BMI to identify the presence of metabolic syndrome (MetSyn).

DESIGN

This was a cross-sectional study using National Health and Nutrition Examination Survey 1999-2006 data.

PARTICIPANTS

A total of 3004 participants aged 12-20 years with dual-energy X-ray absorptiometry body composition and fasting laboratory data participated in the study.

MAIN OUTCOME MEASURES

Adjusted odds ratios for MetSyn according to FMI and LBMI status and area under the curve for the identification of MetSyn were measured.

RESULTS

Receiver-operating characteristic curve analyses identified the 80th percentile for FMI and the 74th percentile for LBMI as the optimal cut points for the identification of MetSyn. There was no difference in the area under the curve for FMI [0.867; 95% confidence interval (CI) 0.838-0.891] vs BMI (0.868; 95% CI 0.837-0.894) Z-scores for MetSyn discrimination. Separate multivariate regression models identified odds ratios for the identification of MetSyn of 6.2 (95% CI 3.3-11.5) for BMI-Z, 6.4 (95% CI 3.7-11.1) for FMI-Z, and 4.6 (95% CI 3.0-7.1) for LBMI-Z. Models containing both FMI-Z and LBMI-Z revealed that greater LBMI-Z was associated with greater odds of low high-density lipoprotein (1.5; 95% CI 1.2-1.9), high blood pressure (1.8; 95% CI 1.1-2.9), and insulin resistance (1.8; 95% CI 1.4-2.5), independent of FMI-Z.

CONCLUSIONS

The use of FMI and LBMI does not improve upon BMI for the identification of MetSyn in the pediatric population. Unexpectedly, higher LBMI was associated with greater odds of multiple cardiometabolic risk factors independent of FMI. The use of FMI and LBMI allow for the independent evaluation of relationships between body compartments and disease and warrants future research.

Impact of body composition during weight change on resting energy expenditure and homeostasis model assessment index in overweight nonsmoking adults

BACKGROUND

Weight change affects resting energy expenditure (REE) and metabolic risk factors. The impact of changes in individual body components on metabolism is unclear.

OBJECTIVE

We investigated changes in detailed body composition to assess their impacts on REE and insulin resistance.

DESIGN

Eighty-three healthy subjects [body mass index (BMI; in kg/m²) range: 20.2-46.8; 50% obese] were investigated at 2 occasions with weight changes between -11.2 and +6.5 kg (follow-up periods between 23.5 and 43.5 mo). Detailed body composition was measured by using the 4-component model and whole-body magnetic resonance imaging. REE, plasma thyroid hormone concentrations, and insulin resistance were measured by using standard methods.

RESULTS

Weight loss was associated with decreases in fat mass (FM) and fat-free mass (FFM) by 72.0% and 28.0%, respectively. A total of 87.9% of weight gain was attributed to FM. With weight loss, sizes of skeletal muscle, kidneys, heart, and all fat depots decreased. With weight gain, skeletal muscle, liver, kidney masses, and several adipose tissue depots increased except for visceral adipose tissue (VAT). After adjustments for FM and FFM, REE decreased with weight loss (by 0.22 MJ/d) and increased with weight gain (by 0.11 MJ/d). In a multiple stepwise regression analysis, changes in skeletal muscle, plasma triiodothyronine, and kidney masses explained 34.9%, 5.3%, and 4.5%, respectively, of the variance in changes in REE. A reduction in subcutaneous adipose tissue rather than VAT was associated with the improvement of insulin sensitivity with weight loss. Weight gain had no effect on insulin resistance.

CONCLUSION

Beyond a 2-compartment model, detailed changes in organ and tissue masses further add to explain changes in REE and insulin resistance.

Moderate weight loss is sufficient to affect thyroid hormone homeostasis and inhibit its peripheral conversion

BACKGROUND

Thyroid hormones are important determinants of energy expenditure, and in rodents, adipose tissue affects thyroid hormone homeostasis via leptin signaling. The relationship between thyroid hormones and nutritional status in humans has been assessed primarily in drastic dietary or bariatric surgery interventions, while limited information is available on serial assessment of this axis during moderate, prolonged dietary restriction.

METHODS

To evaluate the effects of moderate dietary restriction on thyroid hormone homeostasis, 47 subjects with a body mass index (BMI) of 25-45 kg/m(2) were enrolled in a longitudinal intervention study; 30 nonoverweight volunteers were also enrolled as controls. Overweight and obese subjects underwent a 12-month individualized dietary intervention aimed at achieving a 5-10% weight loss.

RESULTS

The intervention resulted in a 6.3±0.9 kg (6.5±1.0%) weight loss. At baseline, thyrotropin (TSH) and T3 concentrations correlated significantly with fat mass (R=0.257, p=0.024 and R=0.318, p=0.005, respectively). After weight loss, T3 decreased significantly (from 112.7±3.1 to 101.8±2.6 ng/dL, p<0.001) in the absence of significant changes in TSH or free T4 (fT4). The decrease in serum T3 correlated with the decrease in weight (R=0.294, p<0.001). The T3:fT4 ratio decreased significantly (p=0.02) in individuals who lost >5% body weight.

CONCLUSIONS

T3 concentration closely correlates with individual nutritional status, and moderate weight loss results in a decrease in T3 with minimal changes in other thyroid hormone homeostasis parameters. The data suggest that a decrease in peripheral conversion of the prohormone T4 into its hormonally active metabolite T3 is at least in part responsible for the observed changes in thyroid hormone homeostasis.

Issues in characterizing resting energy expenditure in obesity and after weight loss

Limitations of current methods: Normalization of resting energy expenditure (REE) for body composition using the 2-compartment model fat mass (FM), and fat-free mass (FFM) has inherent limitations for the interpretation of REE and may lead to erroneous conclusions when comparing people with a wide range of adiposity as well as before and after substantial weight loss.

EXPERIMENTAL OBJECTIVES

We compared different methods of REE normalization: (1) for FFM and FM (2) by the inclusion of %FM as a measure of adiposity and (3) based on organ and tissue masses. RESULTS were compared between healthy subjects with different degrees of adiposity as well as within subject before and after weight loss.

RESULTS

Normalizing REE from an "REE vs. FFM and FM equation" that (1) was derived in obese participants and applied to lean people or (2) was derived before weight loss and applied after weight loss leads to the erroneous conclusion of a lower metabolic rate (i) in lean persons and (ii) after weight loss. This is revealed by the normalization of REE for organ and tissue masses that was not significantly different between lean and obese or between baseline and after weight loss. There is evidence for an increasing specific metabolic rate of FFM with increasing %FM that could be explained by a higher contribution of liver, kidney and heart mass to FFM in obesity. Using "REE vs. FFM and FM equations" specific for different levels of adiposity (%FM) eliminated differences in REE before and after weight loss in women.

CONCLUSION

The most established method for normalization of REE based on FFM and FM may lead to spurious conclusions about metabolic rate in obesity and the phenomenon of weight loss-associated adaptive thermogenesis. Using %FM-specific REE prediction from FFM and FM in kg may improve the normalization of REE when subjects with wide differences in %FM are investigated.

Health and ageing: a cross-sectional study of body composition

BACKGROUND & AIMS

The aim of this work was to provide a complete profile of body composition (BC) in healthy subjects and to investigate age and gender-related differences by dual-energy X-ray absorptiometry (DXA) and its latest developments.

METHODS

Italian volunteers among blood donors were enrolled in 5 different age bands (from 18 to 70 years old) to reach the threshold of 25 males and 25 females per single band (total: 250 subjects). All non-obese subjects who satisfied selective inclusion criteria were measured for weight and height and submitted to DXA, to determine fat mass (FM), non-bone lean mass (LM), bone mineral content and density, at regional and whole-body level. Moreover, the assessment of android visceral FM was performed by a new software.

RESULTS

A decrease in LM and increase in FM was observed with ageing, although the phenomenon was proved to be attenuated in women. The central and visceral redistribution of FM was also shown along lifetime, but women were not affected as men by this change.

CONCLUSIONS

This paper is a report on the status of healthy Italian subjects in their adulthood, to be used as a reference for future investigations on physiology, pathological human conditions, and differences between countries.

Physical training prevents body weight gain but does not modify adipose tissue gene expression

The relationship of body weight (BW) with white adipose tissue (WAT) mass and WAT gene expression pattern was investigated in mice submitted to physical training (PT). Adult male C57BL/6 mice were submitted to two 1.5-h daily swimming sessions (T, N = 18), 5 days/week for 4 weeks or maintained sedentary (S, N = 15). Citrate synthase activity increased significantly in the T group (P < 0.05). S mice had a substantial weight gain compared to T mice (4.06 ± 0.43 vs 0.38 ± 0.28 g, P < 0.01). WAT mass, adipocyte size, and the weights of gastrocnemius and soleus muscles, lung, kidney, and adrenal gland were not different. Liver and heart were larger and the spleen was smaller in T compared to S mice (P < 0.05). Food intake was higher in T than S mice (4.7 ± 0.2 vs 4.0 ± 0.3 g/animal, P < 0.05) but oxygen consumption at rest did not differ between groups. T animals showed higher serum leptin concentration compared to S animals (6.37 ± 0.5 vs 3.11 ± 0.12 ng/mL). WAT gene expression pattern obtained by transcription factor adipocyte determination and differentiation-dependent factor 1, fatty acid synthase, malic enzyme, hormone-sensitive lipase, adipocyte lipid binding protein, leptin, and adiponectin did not differ significantly between groups. Collectively, our results showed that PT prevents BW gain and maintains WAT mass due to an increase in food intake and unchanged resting metabolic rate. These responses are closely related to unchanged WAT gene expression patterns.

Dietary and 24-h fat oxidation in Asians and whites who differ in body composition

BACKGROUND

With the same BMI, age, and sex, Asians were reported to have a higher body fat percentage than whites.

OBJECTIVE

This study aimed to determine the difference in body composition and its effect on dietary and 24-h fat oxidation between Asians and whites when they were fed a diet that contained 30% of energy as fat.

DESIGN

Seventeen Asians (8 men) were matched with 17 whites (8 men) for BMI, age, and sex. Physical activity was measured for 7 d with an accelerometer. During the last 3 d of the activity measurement, subjects were given a diet to maintain energy balances. Energy expenditure and substrate use were measured for 24 h in a respiration chamber. Dietary fat oxidation was determined from the percentage recovery of deuterium in the urine after a breakfast meal that contained deuterated palmitic acid. Body composition was calculated with a 3-compartment model from body mass, body volume (hydrodensitometry), and total body water (deuterium dilution).

RESULTS

Asians had 5% higher body fat than whites (28.1 ± 7.3% compared with 23.0 ± 6.9%, respectively; P = 0.03). The fat-free mass index tended to be lower in Asians than in whites (16.3 ± 1.6 compared with 17.0 ± 1.7 kg/m(2), respectively; P = 0.07). Dietary fat oxidation as a percentage of fat consumed was 11.7 ± 3.6% compared with 10.8 ± 4.5% (P = 0.50) for Asians and whites, respectively. In Asians and whites, the 24-h fat oxidation as a percentage of total energy expenditure was 17.7 ± 6.9% compared with 19.2 ± 5.1% (P = 0.63), respectively; carbohydrate oxidation was 68.0 ± 6.8% compared with 66.1 ± 5.1% (P = 0.51), respectively; and protein oxidation was 14.3 ± 2.2 compared with 14.7 ± 1.6% (P = 0.61), respectively.

CONCLUSION

Dietary and 24-h fat oxidation were not different between Asians and whites despite differences in body composition. This study was registered in the public trial registry at www.ccmo.nl as NL31217.068.10.

Modeling metabolic adaptations and energy regulation in humans

Mathematical modeling of human energy regulation and body weight change has recently reached the level of sophistication required for accurate predictions. Mathematical models are beginning to provide a quantitative framework for integrating experimental data in humans and thereby help us better understand the dynamic imbalances of energy and macronutrients that give rise to changes in body weight and composition. This review provides an overview of the various approaches that have been used to model body weight dynamics and energy regulation in humans, highlights several insights that these models have provided, and suggests how mathematical models can serve as a guide for future experimental research.

Molecular basis of obesity: current status and future prospects

Obesity is a global health problem that is gradually affecting each continent of the world. Obesity is a heterogeneous disorder, and the biological causes of obesity are complex. The rapid increase in obesity prevalence during the past few decades is due to major societal changes (sedentary lifestyle, over-nutrition) but who becomes obese at the individual level is determined to a great extent by genetic susceptibility. In this review, we evidence that obesity is a strongly heritable disorder, and provide an update on the molecular basis of obesity. To date, nine loci have been involved in Mendelian forms of obesity and 58 loci contribute to polygenic obesity, and rare and common structural variants have been reliably associated with obesity. Most of the obesity genes remain to be discovered, but promising technologies, methodologies and the use of “deep phenotyping” lead to optimism to chip away at the ‘missing heritability’ of obesity in the near future. In the longer term, the genetic dissection of obesity will help to characterize disease mechanisms, provide new targets for drug design, and lead to an early diagnosis, treatment, and prevention of obesity.

Resting energy expenditure and protein turnover are increased in patients with severe chronic obstructive pulmonary disease

The mechanisms leading to weight loss in patients with chronic obstructive pulmonary disease (COPD) are poorly understood. Changes in protein metabolism and systemic inflammation may contribute to increased resting energy expenditure (REE) in COPD, leading to an energy imbalance and loss of fat and fat-free mass. The objective of this study was to determine first whether REE was increased in patients with COPD and, second, whether this was associated with increased protein turnover and/or systemic inflammation. Resting energy expenditure was determined using indirect calorimetry in 14 stable outpatients with severe COPD (7 with low and 7 with preserved body mass indices) and 7 healthy controls. Endogenous leucine flux, leucine oxidation, and nonoxidative disposal, indices of whole-body protein breakdown, catabolism, and synthesis, were measured using intravenous infusions of (13)C-bicarbonate and 1-(13)C-leucine. Total body water, from which fat-free mass and fat mass were calculated, was determined using an intravenous bolus of deuterated water. Plasma markers of systemic inflammation were also measured. As a group, subjects with COPD had increased REE adjusted for fat-free mass (P < .001) and faster rates of endogenous leucine flux (P = .006) and nonoxidative leucine disposal (P = .002) compared with controls. There was a significant correlation between REE and both endogenous leucine flux (P = .02) and nonoxidative leucine disposal (P = .008). Plasma concentrations of the inflammatory markers C-reactive protein and interleukin-6 were not different between COPD subjects and controls. Increased rates of protein turnover are associated with increased REE and loss of fat-free mass in COPD.

Adaptive alterations in metabolism: practical consequences on energy requirements in the severely ill patient

PURPOSE OF REVIEW

A recent and large multicentre study reports that ICU patients receive less than half of the recommended energy requirement. This review aims at clarifying whether underfeeding is scientifically justified or sustained by evidence-based medicine.

RECENT FINDINGS

There is evidence that optimal nutrition improves clinical outcome of critically ill patients. The deleterious effect of overfeeding ICU patients is now well acknowledged, but underfeeding is not scientifically justified in ICU patients. Total energy expenditure in ICU patients is variable and methods to predict resting energy expenditure are questionable in these patients.

SUMMARY

There is a need to measure energy expenditure in clinical practice. When not possible, the current guidelines on artificial nutrition (i.e. 25 kcal/kg per day) should be applied in order to limit underfeeding.

Is there evidence for a set point that regulates human body weight?

There is evidence for the idea that there is biological (active) control of body weight at a given set point. Body weight is the product of genetic effects (DNA), epigenetic effects (heritable traits that do not involve changes in DNA), and the environment. Regulation of body weight is asymmetric, being more effective in response to weight loss than to weight gain. However, regulation may be lost or camouflaged by Western diets, suggesting that the failure of biological control is due mainly to external factors. In this situation, the body’s ‘set point’ (i.e., a constant ‘body-inherent’ weight regulated by a proportional feedback control system) is replaced by various ‘settling points’ that are influenced by energy and macronutrient intake in order for the body to achieve a zero energy balance. In a world of abundance, a prudent lifestyle and thus cognitive control are preconditions of effective biological control and a stable body weight. This idea also impacts future genetic research on body weight regulation. Searching for the genetic background of excess weight gain in a world of abundance is misleading since the possible biological control is widely overshadowed by the effect of the environment. In regard to clinical practice, dietary approaches to both weight loss and weight gain have to be reconsidered. In underweight patients (e.g., patients with anorexia nervosa), weight gain is supported by biological mechanisms that may or may not be suppressed by hyperalimentation. To overcome weight loss-induced counter-regulation in the overweight, biological signals have to be taken into account. Computational modeling of weight changes based on metabolic flux and its regulation will provide future strategies for clinical nutrition.

Genetic studies of common types of obesity: a critique of the current use of phenotypes

Recent research into the genetic basis of obesity has focused upon the study of candidate genes, both functional and positional, of genes underlying weight-related Mendelian disorders and of susceptibility loci identified in genome-wide association studies. Three large genome-wide association studies on obesity, together involving more than 150,000 individuals, were published in Nature Genetics last year. The results suggested the involvement of a large number of genetic variants in disease susceptibility. Most genetic effects upon body weight are likely to become obscured by the use of inappropriate phenotypes. In particular, clinical categories such as the body mass index and Metabolic Syndrome do not provide sufficient etiological information for them to be used sensibly in genetic studies on obesity or obesity-related disease. Alleviation of this situation will not come from new genomic research tools, sophisticated statistical algorithms or ever larger sample sizes. Instead, the above notions argue in favour of so-called 'deep phenotyping'.

Laparoscopic biliopancreatic diversion/duodenal switch or laparoscopic Roux-en-Y gastric bypass for super-obesity-weight loss versus side effects

BACKGROUND

Laparoscopic biliopancreatic diversion/duodenal switch (LDS) and laparoscopic Roux-en-Y gastric bypass (LRYGB) are the main surgical options for super-obese patients (body mass index >50 kg/m(2)).

METHODS

We performed a medium long-term evaluation of 13 super-obese patients who had undergone LDS compared with a control group of 19 patients who had undergone LRYGB. The patients were assessed 31 months (range 17-38) and 34 months (range 26-62) after LDS and LRYGB, respectively, for body mass index changes, relief of co-morbidities, nutrition, quality of life, postoperative bowel function, and accumulated healthcare consumption.

RESULTS

The mean body mass index decreased from 54.9 to 30.0 kg/m(2) in the LDS group and 57.8 to 39.8 kg/m(2) in the LRYGB group (P = .005). The hemoglobin A1c level was lower in the LDS group than in the LRYGB group (3.8 +/- .31% versus 4.3 +/- .43%, respectively; P = .01). The LDS patients reported greater energy intake than the LRYGB patients (3132 +/- 1392 kcal versus 2014 +/- 656 kcal, respectively; P = .021). The number of stools daily was 4.1 +/- 3.3 in the LDS group and 1.9 +/- 1.1 in the LRYGB group, P = .0482). Of the 12 patients in the LDS group, 6 reported fecal incontinence or soiling compared with 2 of 16 in the LRYGB group (P = .034). The number of outpatient visits was 5.6 +/- 4.6 for the LDS group and 2.0 +/- 1.9 for the LRYGB group (P = .016), and the number of telephone consultations was 5.0 +/- 5.6 and 1.4 +/- 1.6 for the LDS and LRYGB groups, respectively (P = .043).

CONCLUSION

LDS resulted in greater weight loss than LRYGB in super-obese patients. However, the LDS patients in our series had more frequent gastrointestinal side effects, required greater doses of calcium and vitamin supplementation, and required more postoperative monitoring. Patient satisfaction was high in both groups.