Early childhood growth is associated with cognitive function. However, the independent associations of fat mass (FM) and fat-free mass (FFM) with cognitive function are not well understood. We investigated associations of FM and FFM at birth and 0-5 years accretion with cognitive function at 10 years. Healthy term newborns were enrolled in this cohort. FM and FFM were measured at birth, 1.5, 2.5, 3.5, 4.5, 6 months, 4 and 5 years. Cognitive function was assessed using Peabody Picture Vocabulary Test (PPVT) at 10 years. FM and FFM accretion were computed using statistically independent conditional accretion from 0-3 months, 3-6 months, 6 months-4 years, and 4-5 years. Multiple linear regression was used to assess associations. At the 10-year follow-up, we assessed 318 children with mean (SD) age of 9.8 (1.0) years. A 1 SD higher birth FFM was associated with a 0.14 SD (95% CI: 0.01, 0.28) higher PPVT at 10 years. FFM accretion from 0-3 and 3-6 months was associated with PPVT at 10 year, β = 0.5 SD (95% CI: 0.08, 0.93) and β = -0.48 SD (95% CI: -0.90, -0.07, respectively. FFM accretion after 6 months showed no association with PPVT. Neither FM at birth nor 0-5 years accretion showed association with PPVT. Overall, birth FFM, but not FM was associated with cognitive function at 10 years, while the association of FFM accretion and cognitive function varied across distinct developmental stages in infancy. The mechanisms underlying this varying association between body composition and cognitive function need further investigation.

Within the USA military, monitoring body composition is an essential component of predicting physical performance and establishing soldier readiness. The purpose of this study was to explore mobile phone three-dimensional optical imaging (3DO), a user-friendly technology capable of rapidly obtaining reliable anthropometric measurements and to determine the validity of the new Army one-site body fat equations using 3DO-derived abdominal circumference. Ninety-six participants (51 F, 45 M; age: 23·7 ± 6·5 years; BMI: 24·7 ± 4·1 kg/m2) were assessed using 3DO, dual-energy X-ray absorptiometry (DXA) and a 4-compartment model (4C). The validity of the Army equations using 3DO abdominal circumference was compared with 4C and DXA estimates. Compared with the 4C model, the Army equation overestimated BF% and fat mass (FM) by 1·3 ± 4·8 % and 0·9 ± 3·4 kg, respectively, while fat-free mass (FFM) was underestimated by 0·9 ± 3·4 kg (P < 0·01 for each). Values from DXA and Army equation were similar for BF%, FM and FFM (constant errors between −0·1 and 0·1 units; P ≥ 0·82 for each). In both comparisons, notable proportional bias was observed with slope coefficients of −0·08 to −0·43. Additionally, limits of agreement were 9·5–10·2 % for BF% and 6·8–7·8 kg for FM and FFM. Overall, while group-level performance of the one-site Army equation was acceptable, it exhibited notable proportional bias when compared with laboratory criterion methods and wide limits of agreement, indicating potential concerns when applied to individuals. 3DO may provide opportunities for the development of more advanced, automated digital anthropometric body fat estimation in military settings.

This study verified the accuracy of the international BMI references and the allometric BMI reference to diagnose obesity in children and adolescents from the USA. Data from 17 313 subjects were obtained from the National Health and Nutrition Examination Survey between the years 1999–2006 and 2011–2018. Fat Mass Index, Allometric Fat Mass Index and fat mass/fat-free mass were calculated. Receiver operating characteristic curve, AUC, sensitivity, specificity, positive likelihood ratio and negative likelihood ratio were estimated to evaluate the accuracy of the growth references for diagnosing obesity. The International Obesity Task Force, MULT BMI 17 years, MULT BMI 18 years and allometric BMI 19 years achieved the best sensitivity-specificity trade-off for boys, with sensitivities ranging from 0·92 to 0·96 and specificities of 0·94, with positive likelihood ratio of 15·51, 16·17, 13·46 and 18·01, respectively. The negative likelihood ratios were notably low, ranging from 0·04 to 0·08. In girls, the International Obesity Task Force, MULT BMI 17 years and MULT allometric BMI 17 years also demonstrated high sensitivity (0·95–0·97) and specificity (0·92), with positive likelihood ratio values of 11·54, 11·82 and 11·77, respectively and low negative likelihood ratio values (0·03–0·05). In summary, these international growth references presented satisfactory performance to diagnose obesity. However, the MULT growth reference performed better, and the MULT allometric BMI was the only indicator capable of detecting that girls have a higher proportion of fat mass than boys for the same index values. These findings suggest that the MULT growth reference may be a better tool to assess the nutritional status of children and adolescents internationally.

The objective of this prospective observational study was to assess the growth and body composition of term small-for-gestational-age (SGA) infants from birth to 6 months and evaluate the effect of catch-up growth (CUG) on body composition. Term SGA newborns were recruited at birth. Anthropometry and body composition were evaluated at 3 days, 6, 10 and 14 weeks, and 6 months. Fat and fat-free mass (FM and FFM) were compared between infants with and without CUG (increase in weight Z-score by > 0·67) by air displacement plethysmography. Factors that could affect body composition and CUG, including parents’ BMI and stature, infants’ birth weight, sex and feeding, were evaluated. A total of 143 SGA newborns (sixty-six boys) with birth weight of 2336 (sd 214) g were enrolled; 109 were followed up till 6 months. Median weight Z-score increased from −2·3 at birth to −1·3 at 6 months, with 51·9 % of infants showing CUG. Infants with CUG had higher FM (1796 (sd 491) g v. 1196 (sd 474) g, P < 0·001) but similar FFM (4969 (sd 508) g v. 4870 (sd 622) g, P = 0·380), and consequently higher FM percentage (FM%) (26·5 (sd 5·8) v. 19·7 (sd 6·9), P < 0·001), compared with those without CUG. Lower birth weight, exclusive breast-feeding and higher parental stature were positively associated with CUG. In conclusion, CUG in term SGA infants in the first 6 months of life was almost entirely attributable to greater gain in FM. Follow-up of this cohort will provide insight into the long-term effect of disproportionate gain in FM in early infancy in SGA babies.

Research indicates that green tea extract (GTE) supplementation is beneficial for a range of conditions, including several forms of cancer, CVD and liver diseases; nevertheless, the existing evidence addressing its effects on body composition, oxidative stress and obesity-related hormones is inconclusive. This systematic review and meta-analysis aimed to investigate the effects of GTE supplementation on body composition (body mass (BM), body fat percentage (BFP), fat mass (FM), BMI, waist circumference (WC)), obesity-related hormones (leptin, adiponectin and ghrelin) and oxidative stress (malondialdehyde (MDA) and total antioxidant capacity (TAC)) markers. We searched proper databases, including PubMed/Medline, Scopus and Web of Science, up to July 2022 to recognise published randomised controlled trials (RCT) that investigated the effects of GTE supplementation on the markers mentioned above. A random effects model was used to carry out a meta-analysis. The heterogeneity among the studies was assessed using the I2 index. Among the initial 11 286 studies identified from an electronic database search, fifty-nine studies involving 3802 participants were eligible to be included in this meta-analysis. Pooled effect sizes indicated that BM, BFP, BMI and MDA significantly reduced following GTE supplementation. In addition, GTE supplementation increased adiponectin and TAC, with no effects on FM, leptin and ghrelin. Certainty of evidence across outcomes ranged from low to high. Our results suggest that GTE supplementation can attenuate oxidative stress, BM, BMI and BFP, which are thought to negatively affect human health. Moreover, GTE as a nutraceutical dietary supplement can increase TAC and adiponectin.

Systolic blood pressure (SBP) is significantly associated with body composition in children and adolescents. However, which one of the components of body composition is the dominant contributor to SBP in children and adolescents remains unclear. We, therefore, aimed to determine the dominant contributor to SBP among components of body composition in a large cohort of American children and adolescents derived from the National Health and Nutrition Examination Survey with cross-sectional analysis. In total, 13 618 children and adolescents (median age 13 years; 6107 girls) with available data on whole-body dual-emission X-ray absorptiometry measurements were included. Multiple linear regression showed that SBP was associated with higher total fat-free mass in boys (β = 0·49, P < 0·001) and girls (β = 0·47, P < 0·001) and with higher total fat mass only in boys (β = 0·12, P < 0·001) after adjustment for covariates. When taking fat distribution into consideration, SBP was associated with higher trunk fat mass (boys: β = 0·28, P < 0·001; girls: β = 0·15, P < 0·001) but negatively associated with leg fat mass (Boys: β = −0·14, P < 0·001; Girls: β = −0·11, P < 0·001), in both boys and girls. Dominance analysis showed that total fat-free mass was the dominant contributor to SBP (boys: 49 %; girls: 55·3 %), followed by trunk fat mass (boys: 32·1 %; girls: 26·9 %); leg fat mass contributed the least to SBP in boys (18·9 %) and girls (17·8 %). Our findings indicated that total fat-free mass was not only associated with SBP but also the most dominant contributor to SBP variation in American children and adolescents.

Maternal psychosocial stress is associated with delivery of both small- and large-for-gestational-age newborns. Prior studies have relied on methods that do not capture fat mass (FM) vs. fat-free mass (FFM). We aimed to assess the relationship of maternal psychosocial stress, using the Edinburgh Postnatal Depression Scale (EPDS) and Cohen’s Perceived Stress Scale (PSS), with newborn body composition. The sample included 604 mother/newborn pairs in the Healthy Start study. We used linear regression to examine associations of EPDS (>6.5 vs. ≤6.5) and PSS (>21 vs. ≤21) with newborn adiposity (FM and %FM measured by air displacement plethysmography [ADP], BMI-for-age, weight-for-length, and weight-for-age z-scores) and lean mass (FFM and length-for-age z-score). Average age of the women was 29.2 ± 6 y. Fifty-five percent of the women were white, 26.2% Hispanic, and 12.1% Black. Twenty-four percent of women had EPDS >6.5 and 18.1% had PSS >21. Mean ± SD birthweight was 3136 ± 437 g. After adjustment for confounders, EPDS >6.5 vs. ≤6.5 corresponded with 35.3 (95% CI: 6.6, 64.0) g lower offspring FM and 0.18 (−0.03, 0.39) units shorter length z-score. PSS was not associated with any neonatal outcomes. Maternal psychosocial stress is associated with delivery of shorter newborns with less FM.

Prior meta-analytic investigations over a decade ago rather inconclusively indicated that conjugated linoleic acid (CLA) supplementation could improve anthropometric and body composition indices in the general adult population. More recent investigations have emerged, and an up-to-date systematic review and meta-analysis on this topic must be improved. Therefore, this investigation provides a comprehensive systematic review and meta-analysis of randomised controlled trials (RCT) on the impact of CLA supplementation on anthropometric and body composition (body mass (BM), BMI, waist circumference (WC), fat mass (FM), body fat percentage (BFP) and fat-free mass (FFM)) markers in adults. Online databases search, including PubMed, Scopus, the Cochrane Library and Web of Science up to March 2022, were utilised to retrieve RCT examining the effect of CLA supplementation on anthropometric and body composition markers in adults. Meta-analysis was carried out using a random-effects model. The I2 index was used as an index of statistical heterogeneity of RCT. Among the initial 8351 studies identified from electronic databases search, seventy RCT with ninety-six effect sizes involving 4159 participants were included for data analyses. The results of random-effects modelling demonstrated that CLA supplementation significantly reduced BM (weighted mean difference (WMD): −0·35, 95 % CI (−0·54, −0·15), P < 0·001), BMI (WMD: −0·15, 95 % CI (−0·24, −0·06), P = 0·001), WC (WMD: −0·62, 95% CI (−1·04, −0·20), P = 0·004), FM (WMD: −0·44, 95 % CI (−0·66, −0·23), P < 0·001), BFP (WMD: −0·77 %, 95 % CI (−1·09, −0·45), P < 0·001) and increased FFM (WMD: 0·27, 95 % CI (0·09, 0·45), P = 0·003). The high-quality subgroup showed that CLA supplementation fails to change FM and BFP. However, according to high-quality studies, CLA intake resulted in small but significant increases in FFM and decreases in BM and BMI. This meta-analysis study suggests that CLA supplementation may result in a small but significant improvement in anthropometric and body composition markers in an adult population. However, data from high-quality studies failed to show CLA’s body fat-lowering properties. Moreover, it should be noted that the weight-loss properties of CLA were small and may not reach clinical importance.

Nutrition plays an important role in improving sports performance. The present study aimed at nutritional assessment and examined the relationship between athletic performance and body composition in soccer referees at different levels. The study participants were 120 male soccer referees. 5, 10 and 30 metres (m) sprint tests to measure speed and cooper test for physical fitness were applied in the referees. Participants were divided into two groups as city and class soccer referee. The anthropometric measurements, excluding fat mass (FM) (%), were higher in class referees. Fat mass (%) differences (14⋅1 ± 4⋅28 v. 12⋅3 ± 4⋅41) were statistically significant (P < 0⋅05). Daily energy and nutrient intakes were similar. The inadequacy percentages of energy, vitamin A and calcium were the highest (29⋅2, 30⋅0 and 34⋅2 %, respectively). It was found that a negative significant correlation between FM% and cooper test score (P < 0⋅01; r = −0⋅35), a positive significant correlation between FM% and 5, 10 and 30 m sprint test scores (P < 0⋅01, r = 0⋅38; P < 0⋅01, r = 0⋅38 and P < 0⋅01, r = 0⋅48, respectively). Similarly, there was a negative significant correlation between waist circumference (WC) and cooper test score (P < 0⋅01; r = −0⋅31), a positive significant correlation between WC and 5, 10 and 30 m sprint test scores (P < 0⋅01, r = 0⋅33; P < 0⋅01, r = 0⋅40; P < 0⋅01, r = 0⋅33, respectively). Nutritional recommendations for soccer referees should be made specific to the individual, considering body composition, training intensity and match frequency by a dietician.

Studying factors that contribute to our understanding of maintaining normal energy balance are of paramount significance following spinal cord injury (SCI). Accurate determination of energy needs is crucial for providing nutritional guidance and managing the increasing prevalence of malnutrition or obesity after SCI. BMR represents 75–80 % of the total energy expenditure in persons with SCI. Accurately measuring BMR is an important component for calculating total energetic needs in this population. Indirect calorimetry is considered the gold-standard technique for measuring BMR. However, technical challenges may limit its applications in large cohort studies and alternatively rely on prediction equations. Previous work has shown that BMR changes in response to disuse and exercise in the range of 15–120 %. Factors including sex, level of injury and type of assistive devices may influence BMR after SCI. RMR is erroneously used interchangeably for BMR, which may result in overestimation of energetic intake when developing nutritional plans. To address this concern, we comprehensively reviewed studies that conducted BMR (n=15) and RMR (n=22) in persons with SCI. The results indicated that RMR is 9 % greater than BMR in persons with SCI. Furthermore, the SCI-specific prediction equations that incorporated measures of fat-free mass appeared to accurately predict BMR. Overall, the current findings highlighted the significance of measuring BMR as well as encouraging the research and clinical community to effectively establish countermeasures to combat obesity after SCI.

This systematic review and meta-analysis aimed to investigate the effects of beetroot (BR) or nitrate supplements on body composition indices. A systematic search was conducted for randomised controlled trials (RCT) published up to August 2022 among online databases including Scopus, PubMed/Medline, Web of Science and Embase. Meta-analyses were carried out using a random-effects model. The I2 index was used to assess the heterogeneity of RCT. A total of twelve RCT met the inclusion criteria for this meta-analysis. The pooled effect size of included studies indicated that BR or nitrate supplementation did not change body weight (weighted mean differences (WMD): –0·14 kg, 95 % CI –1·22, 1·51; P = 0·836; I2 = 0 %), BMI (WMD: −0·07 kg/m2, 95 % CI −0·19,0·03; P = 0·174, I2 = 0 %), fat mass (WMD: –0·26 kg, 95 % CI –1·51, 0·98; P = 0·677, I2 = 0 %), waist circumference (WMD: –0·28 cm, 95 % CI –2·30, 1·74; P = 0·786, I2 = 0 %), body fat percentage (WMD: 0·18 %, 95 % CI –0·62, 0·99; P = 0·651, I2 = 0 %), fat-free mass (WMD: 0·31 kg, 95 % CI –0·31, 1·94; P = 0·703, I2 = 0 %) and waist-to-hip ratio (WMD: 0, 95 % CI –0·01, 0·02; P = 0·676, I2 = 0 %). Subgroup analyses based on trial duration, BR or nitrate dose, study design, baseline BMI and athletic status (athlete v. non-athlete) demonstrated similar results. Certainty of evidence across outcomes ranged from low to moderate. This meta-analysis study suggests that BR or nitrate supplements cannot efficiently ameliorate body composition indices regardless of supplement dosage, trial duration and athletic status.

Smartphone applications (SPA) now offer the ability to provide accessible in-home monitoring of relevant individual health biomarkers. Previous cross-sectional validations of similar technologies have reported acceptable accuracy with high-grade body composition assessments; this research assessed longitudinal agreement of a novel SPA across a self-managed weight loss intervention of thirty-eight participants (twenty-one males, seventeen females). Estimations of body mass (BM), body fat percentage (BF%), fat-free mass (FFM) and waist circumference (WC) from the SPA were compared with ground truth (GT) measures from a dual-energy X-ray absorptiometry scanner and expert technician measurement. Small mean differences (MD) and standard error of estimate (SEE) were observed between method deltas (ΔBM: MD = 0·12 kg, SEE = 2·82 kg; ΔBF%: MD = 0·06 %, SEE = 1·65 %; ΔFFM: MD = 0·17 kg, SEE = 1·65 kg; ΔWC: MD = 1·16 cm, SEE = 2·52 cm). Concordance correlation coefficient (CCC) assessed longitudinal agreement between the SPA and GT methods, with moderate concordance (CCC: 0·55–0·73) observed for all measures. The novel SPA may not be interchangeable with high-accuracy medical scanning methods yet offers significant benefits in cost, accessibility and user comfort, in conjunction with the ability to monitor body shape and composition estimates over time.

While there is an increasing prevalence of dieting in the overall population, weight loss (WL) practices could be a risk factor for weight gain (WG) in normal-weight (NW) individuals. The aim of the present work was to systematically review all the studies implicating diet restriction and body weight (BW) evolution in NW people. The literature search was registered in PROSPERO (CRD42021281442) and was performed in three databases from April 2021 to June 2022 for articles involving healthy NW adults. From a total of 1487 records initially identified, eighteen were selected in the systematic review. Of the eight dieting interventional studies, only one found a higher BW after weight recovery, but 75 % of them highlighted metabolic adaptations in response to WL favouring weight regain and persisting during/after BW recovery. Eight of the ten observational studies showed a relationship between dieting and major later WG, while the meta-analysis of observational studies results indicated that ‘dieters’ have a higher BW than ‘non-dieters’. However, considering the high methodological heterogeneity and the publication bias of the studies, this result should be taken with caution. Moreover, the term ‘diet’ was poorly described, and we observed a large heterogeneity of the methods used to assess dieting status. Present results suggest that dieting could be a major risk factor for WG in the long term in NW individuals. There is, however, a real need for prospective randomised controlled studies, specifically assessing the relationship between WL induced by diet and subsequent weight in this population.

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.

Exercise and dietary interventions have been described to positively affect metabolic syndrome (MetS) via molecular-induced changes. The purpose of this study was to investigate the effects of dietary carbohydrate restriction and aerobic exercise (AE) on retinol binding protein 4 (RBP4) and fatty acid binding protein 5 (FABP5) in middle-aged men with MetS. The study had a randomised, double-blinded, parallel-controlled design. Forty middle-aged men with MetS (age: 53·97 ± 2·85 years, BMI = 31·09 ± 1·04 kg/m2) were randomly assigned to four groups, AE (n 10), ketogenic diet (KD; n 10), AE combined with KD (AE + KD; n 10) or control (C; n 10). RBP4, FABP5, body composition (body mass, BMI and body fat), insulin resistance, insulin sensitivity and MetS factors were evaluated prior to and after the 12-week intervention. AE + KD significantly decreased the body fat percentage (P = 0·006), BMI (P = 0·001), Zmets (P = 0·017), RBP4 (P = 0·017) and the homeostasis model of insulin resistance (HOMA-IR) (P = 0·001) as compared with control group and marginally significantly decreased the Zmets as compared with exercise group (P = 0·086). KD significantly decreased RBP4 levels as compared with control group (P = 0·041). Only the AE intervention (P = 0·045) significantly decreased FABP5 levels. Combining intervention of carbohydrate restriction with AE compared with carbohydrate restriction and AE alone improved RBP4, HOMA-IR as well as different body composition and MetS factors in middle-aged men with MetS.

Compromised nutritional status is associated with a poor prognosis in chronic obstructive pulmonary disease (COPD) patients. However, the impact of nutritional support in this group of patients is controversial. The present study systematically reviewed the effect of energy and or protein supplements or food fortification on anthropometry and muscle strength of COPD patients. We searched MEDLINE (PubMed), EMBASE, Cochrane Library and Scopus for all published randomised clinical trials without language restriction up to May 2021. Three reviewers performed study selection and data extraction independently. We judged the risk of bias by RoB 2 and the certainty of evidence by the GRADE approach. We included thirty-two randomised controlled trials and compiled thirty-one of them (1414 participants) in the random-effects model meta-analyses. Interventions were energy and/or protein oral nutritional supplements or food fortification added to the diet for at least one week. Pooled analysis revealed that nutritional interventions increased body weight (muscle circumference (MD) = 1·44 kg, 95 % CI 0·81, 2·08, I2 = 73 %), lean body mass (standardised mean difference (SMD) = 0·37; 95 % CI 0·15, 0·59, I2 = 46 %), midarm muscle circumference (MD = 0·29 mm2, 95 % CI 0·02, 0·57, I2 = 0 %), triceps skinfold (MD = 1·09 mm, 95 % CI 0·01, 2·16, I2 = 0 %) and handgrip strength (SMD = 0·39, 95 % CI 0·07, 0·71, I2 = 62 %) compared with control diets. Certainty of evidence ranged from very low to low, and most studies were judged with some concerns or at high risk of bias. This meta-analysis revealed, with limited evidence, that increased protein and/or energy intake positively impacts anthropometric measures and handgrip strength of COPD patients.

Few investigations have evaluated the validity of current body composition technology among racially and ethnically diverse populations. This study assessed the validity of common body composition methods in a multi-ethnic sample stratified by race and ethnicity. One hundred and ten individuals (55 % female, age: 26·5 (sd 6·9) years) identifying as Asian, African American/Black, Caucasian/White, Hispanic, Multi-racial and Native American were enrolled. Seven body composition models (dual-energy X-ray absorptiometry (DXA), air displacement plethysmography (ADP), two bioelectrical impedance devices (BIS, IB) and three multi-compartment models) were evaluated against a four-compartment criterion model by assessing total error (TE) and standard error of the estimate. For the total sample, measures of % fat and fat-free mass (FFM) from multi-compartment models were all excellent to ideal (% fat: TE = 0·94–2·37 %; FFM: TE = 0·72–1·78 kg) compared with the criterion. % fat measures were very good to excellent for DXA, ADP and IB (TE = 2·52–2·89 %) and fairly good for BIS (TE = 4·12 %). For FFM, single device estimates were good (BIS; TE = 3·12 kg) to ideal (DXA, ADP, IB; TE = 1·21–2·15 kg). Results did not vary meaningfully between each race and ethnicity, except BIS was not valid for African American/Black, Caucasian/White and Multi-racial participants for % fat (TE = 4·3–4·9 %). The multi-compartment models evaluated can be utilised in a multi-ethnic sample and in each individual race and ethnicity to obtain highly valid results for % fat and FFM. Estimates from DXA, ADP and IB were also valid. The BIS may demonstrate greater TE for all racial and ethnic cohorts and results should be interpreted cautiously.

Obesity is associated with increased muscle mass and muscle strength. Methods taking into account the total body mass to reveal obese older individuals at increased risk of functional impairment are needed. Therefore, we aimed to detect methods to identify obese older adults at increased risk of functional impairment. Home-dwelling older adults (n 417, ≥ 70 years of age) were included in this cross-sectional study. Sex-specific cut-off points for two obesity phenotypes (waist circumference (WC) and body fat mass (FM %)) were used to divide women and men into obese and non-obese groups, and within-sex comparisons were performed. Obese women and men, classified by both phenotypes, had similar absolute handgrip strength (HGS) but lower relative HGS (HGS/total body mass) (P < 0·001) than non-obese women and men, respectively. Women with increased WC and FM %, and men with increased WC had higher appendicular skeletal muscle mass (P < 0·001), lower muscle quality (HGS/upper appendicular muscle mass) (P < 0·001), and spent longer time on the stair climb test and the repeated sit-to-stand test (P < 0·05) than non-obese women and men, respectively. Absolute muscle strength was not able to discriminate between obese and non-obese older adults. However, relative muscle strength in particular, but also muscle quality and physical performance tests, where the total body mass was taken into account or served as an extra load, identified obese older adults at increased risk of functional impairment. Prospective studies are needed to determine clinically relevant cut-off points for relative HGS in particular.

Previous studies evaluating the effects of betaine supplementation on body composition offer contradictory findings. This systematic review and meta-analysis assessed the effects of betaine supplementation on body composition indices (body mass (BM), BMI, body fat percentage (BFP), fat mass (FM), fat-free mass (FFM)), and dietary intakes. Studies examining the effects of betaine supplementation on body composition and dietary intakes published up to August 2021 were identified through PubMed, the Cochrane Library, Web of Science, Embase, SCOPUS and Ovid databases. Betaine supplementation failed to significantly affect BM ((weighted mean difference (WMD): −0·40 kg, 95 % CI −1·46, 0·64), P = 0·447), BMI ((WMD: −0·05 kg/m2, 95 % CI −0·36, 0·25), P = 0·719), BFP ((WMD: 0·26 %, 95 % CI −0·82, 1·36), P = 0·663), FM ((WMD: −0·57 kg, 95 % CI −2·14, 0·99), P = 0·473) and FFM ((WMD: 0·61 kg, 95 % CI −1·27, 2·49), P = 0·527). Subgroup analyses based on participant’s age (< 40 and > 40 years), sex, BMI, trial duration (< 8 and ≥ 8 weeks), betaine supplementation dosage (< 4 and ≥ 4 g) and health status (healthy or unhealthy) demonstrated similar results. Other than a potential negligible increase in protein intake (WMD: 3·56 g, 95 % CI 0·24, 6·88, P = 0·035), no changes in dietary intakes were observed following betaine supplementation compared with control. The present systematic review and meta-analysis does not show any beneficial effects of betaine supplementation on body composition indices (BM, BMI, FM and FFM).