The association between obesity and asthma: interactions between systemic and airway inflammation.

RATIONALE: Both obesity and asthma are common conditions, and both are characterized by the presence of inflammation. Animal studies suggest that the development of airway hyperresponsiveness with antigen challenge is exaggerated with obesity. However, clear evidence for either an additive or a synergistic pathologic interaction between obesity and asthma is lacking in humans. OBJECTIVES: To identify whether an interaction between systemic and local inflammation occurs in obese subjects with asthma in a controlled observational study. METHODS: We studied 79 women: obese patients with asthma (n = 20), normal-weight patients with asthma (n = 19), obese patients without asthma (n = 20), and normal-weight patients without asthma (n = 20). After corticosteroid withdrawal, between-group differences in spirometric values, lung volumes, exhaled nitric oxide, induced sputum cell counts, and biomarkers of inflammation in sputum supernatant and blood were measured, and interactions explored. MEASUREMENTS AND MAIN RESULTS: Markers of systemic inflammation were increased with obesity, and Th2 cytokines were increased with asthma, but no important interactions were identified. Obesity adversely affected lung function with increases in functional residual capacity and residual volume in obese but not normal-weight patients with asthma, with a significant obesity by asthma interaction. CONCLUSIONS: The link between obesity and asthma is unlikely to be explained by enhancement of the "classical" forms of airway inflammation resulting from the systemic inflammatory effects of obesity itself. Other mechanisms, possibly related to innate immunity, may explain the relationship between obesity and asthma.

Body mass index status is effective in identifying metabolic syndrome components and insulin resistance in Pacific Island teenagers living in New Zealand.

Although adults of Pacific ethnicity living in New Zealand have more than double the prevalence of diabetes and cardiovascular disease than the general population, little is known regarding the presence of risk factors for these disorders among young Pacific Islanders. The study aim was to examine relationships between body composition, glucose and lipid metabolism, and components of the metabolic syndrome (MS) in a community sample of Pacific Island (PI) teenagers living in Dunedin. Anthropometry, body composition (dual-energy x-ray absorptiometry), glucose and lipid metabolism, insulin resistance (homeostasis model assessment [HOMA2], McAuley index), and components of MS were assessed in 80 PI teenagers (aged 15-18 years). Results showed that 6 participants had full MS, 2 had high fasting blood glucose values (>7.0 mmol/L), 55 had high adiposity, and 21 had insulin resistance. Assessment of the components of MS by body mass index (BMI) status showed that obese participants (n = 29) had a high prevalence (86.2% had one or more component), whereas only 10.5% of those with healthy BMI status (n = 19) had any MS component. Elevated fat mass had substantial effects on fasting insulin values, HOMA2, and the McAuley index because in data adjusted for age, sex, and lean mass, a 10% greater fat mass was associated with a 4.7% increase in fasting insulin, a 5.3% rise in HOMA2, and a 2.3% decrease in the McAuley index. Our results suggest that the antecedents of cardiovascular disease and type 2 diabetes mellitus occur frequently in young Pacific Islanders having high adiposity. We conclude that community studies of PI adolescents should focus on assessing risk factors whenever BMI values are high.

Ethnic differences in extreme obesity.

A nationwide representative survey of New Zealand schoolchildren showed a 2.7% incidence of extreme obesity (versus 4% in the United States) but revealed worrying ethnic differences in prevalence. Prevalence percentages (95% CI) were 0.8 (0.4 to 1.9), 5.1 (3.6 to 7.1), and 10.9 (8.9 to 13.3) in New Zealand European, Maori, and Pacific Island groups, respectively. These findings warrant remedial action.

Bone and body composition of children and adolescents with repeated forearm fractures.

UNLABELLED: DXA measurements in 90 children and adolescents with repeated forearm fractures showed reduced ultradistal radius BMC and BMD values and elevated adiposity, suggesting site-specific bone weakness and high body weight increase fracture risk. Symptoms to cow milk, low calcium intakes, early age of first fracture, and overweight were over-represented in the sample. INTRODUCTION: Although many apparently healthy children fracture their forearms repeatedly during growth, no previous studies of their bone health and body composition have been undertaken. Nor has the prevalence of established risk factors for fracture in such a population been assessed. MATERIALS AND METHODS: Ninety children and adolescents (47 girls and 43 boys) 5-19 years of age, who had experienced at least two fractures of the forearm, were studied. Bone size and mineralization were assessed using DXA at the ultradistal radius, one-third radius, neck of femur, hip trochanter, lumbar spine, and total body. Total body lean mass and fat mass were also determined. The prevalence of six risk factors for fracture were also examined, and their influence on ultradistal BMC Z scores was assessed. RESULTS: Participants experienced 295 fractures (74.9% forearm). Children with an early age of first fracture had higher rates of fracture per l00 years of exposure than those fracturing later. Four risk factors for fracture were over-represented in observed versus expected percentages: early age of first fracture (27.7% versus 11.3%), adverse symptoms to cow milk (22.2% versus 6.7%), low dietary calcium intake (20% versus 4.5%), and overweight (33.3% versus 15.5%). However, physical activity levels were similar to the reference population. Z scores for BMC and BMD were reduced, particularly at the ultradistal radius, whereas Z scores for weight, body mass index, fat mass, and body fat percentage were increased. Mean (SD) BMC Z scores were lowest at the ultradistal radius, -0.66 (1.22), where symptoms to milk were associated with reduced values (p < 0.009) and overweight with increased values (p < 0.003). CONCLUSIONS: Our results suggest site-specific weakness and high body weight contribute to fracture risk in children and adolescents who fracture their forearms repeatedly. These findings are consonant with work showing adult Colles fractures increase as ultradistal radius BMD falls and with evidence that overweight children and adolescents are fracture prone.

Intensive lifestyle changes are necessary to improve insulin sensitivity: a randomized controlled trial.

OBJECTIVE: The extent to which lifestyle must be altered to improve insulin sensitivity has not been established. This study compares the effect on insulin sensitivity of current dietary and exercise recommendations with a more intensive intervention in normoglycemic insulin-resistant individuals. RESEARCH DESIGN AND METHODS: Seventy-nine normoglycemic insulin-resistant (determined by the euglycemic insulin clamp) men and women were randomized to either a control group or one of two combined dietary and exercise programs. One group (modest level) was based on current recommendations and the other on a more intensive dietary and exercise program. Insulin sensitivity was measured using a euglycemic insulin clamp, body composition was measured using dual-energy X-ray absorptiometry, and anthropometry and aerobic fitness were assessed before and after a 4-month intervention period. Four-day dietary intakes were recorded, and fasting glucose, insulin, and lipids were measured. RESULTS: Only the intensive group showed a significant improvement in insulin sensitivity (23% increase, P=0.006 vs. 9% in the modest group, P=0.23). This was associated with a significant improvement in aerobic fitness (11% increase in the intensive group, P=0.02 vs. 1% in the modest group, P=0.94) and a greater fiber intake, but no difference in reported total or saturated dietary fat. CONCLUSIONS: Current clinical dietary and exercise recommendations, even when vigorously implemented, did not significantly improve insulin sensitivity; however, a more intensive program did. Improved aerobic fitness appeared to be the major difference between the two intervention groups, although weight loss and diet composition may have also played an important role in determining insulin sensitivity.

Prediction of Fat-Free Mass in Children.

BACKGROUND: Fat-free mass (FFM) is an important covariate for predicting drug clearance. Models for predicting FFM have been developed in adults but there is currently a paucity of mechanism-based models developed to predict FFM in children. OBJECTIVE: The aim of this study was to develop and evaluate a model to predict FFM in children. METHODS: A large dataset (496 females and 515 males) was available for model building. Subjects had a relatively wide range of age (3-29 years) and body mass index values (12-44.9 kg/m(2)). Two types of models (M1 and M2) were developed to describe FFM in children. M1 was fully empirical and based on a linear model that contained all statistically significant covariates and their interactions. M2 was a simpler model that incorporated a maturation process. M1 was developed to provide the best possible description of the data (i.e. a positive control). In addition, a published adult model (M3) was applied directly as a reference description of the data. The predictive performances of the three models were assessed by visual predictive checks and by using mean error (ME) and root mean squared error (RMSE). A test dataset (90 females and 86 males) was available for external evaluation. RESULTS: M1 consisted of nine terms with up to second-level interactions. M2 was a sigmoid hyperbolic model based on postnatal age with an asymptote at the adult prediction (M3). For the index dataset, the ME and 95 % CI for M1, M2 and M3 were 0.09 (0.03-0.16), 0.24 (0.14-0.33) and 0.29 (0.06-0.51) kg, respectively, and RMSEs were 1.12 (1.03-1.23), 1.58 (1.46-1.72) and 3.76 (3.54-3.97) kg. CONCLUSIONS: A maturation model that asymptoted to an established adult model was developed for prediction of FFM in children. This model was found to perform well in both male and female children; however, the adult model performed similarly to the maturation model for females. The ability to predict FFM in children from simple demographic measurements is expected to improve understanding of human body structure and function with direct application to pharmacokinetics.

Four-year gain in bone mineral in girls with and without past forearm fractures: a DXA study. Dual energy X-ray absorptiometry.

We have previously shown that girls with a recent distal forearm fracture have weaker skeletons than girls who have never fractured. This could be a transient or persistent phenomenon. The present study was undertaken to determine whether the bone mineral content (BMC) of girls with previous distal forearm fractures remains lower 4 years postfracture or if catch-up gain has occurred. We report baseline and follow-up dual energy X-ray absorptiometry (DXA) results for 163 girls: 81 girls from the original control group who remained free of fracture (group 1) and 82 girls from the original group with distal forearm fractures (group 2). In data adjusted for bone area, height, weight, and pubertal status, group 2 girls had 3.5-8.5% less BMC at the total body, lumbar spine, ultradistal radius, and hip trochanter than group 1 at baseline, and 2.4-5.7% less BMC at these sites at follow-up. Even girls from group 2 who did not experience another fracture after baseline (n = 58) did not display greater BMC at follow-up compared with baseline values at any site, indicating that the decreased BMC at the time of fracture had persisted. In group 2, the relative gain in BMC after adjusting for the initial BMC and current bone area, height, weight, and pubertal stage was less than or similar to, but not greater than that of group 1 (ratio [95% CI]: total body, 0.985 [0.972-0.998]; lumbar spine, 0.961 [0.935-0.987]; ultradistal radius, 0.968 [0.939-0.998]; hip trochanter, 0.955 [0.923-0.988]; femoral neck, 0.981 [0.956-1.007]; and 33% radius 0.999 [0.977-1.021]). These findings indicate that girls with distal forearm fractures do not improve their gain of BMC. We conclude that girls who have sustained a distal forearm fracture maintain their lower BMC at most sites for at least 4 years.

Children who avoid drinking cow milk have low dietary calcium intakes and poor bone health.

BACKGROUND: Information concerning the adequacy of bone mineralization in children who customarily avoid drinking cow milk is sparse. OBJECTIVE: The objective was to evaluate dietary calcium intakes, anthropometric measures, and bone health in prepubertal children with a history of long-term milk avoidance. DESIGN: We recruited 50 milk avoiders (30 girls, 20 boys) aged 3-10 y by advertisement. We measured current dietary calcium intakes with a food-frequency questionnaire and body composition and bone mineral density with dual-energy X-ray absorptiometry and compared the results with those of 200 milk-drinking control children. RESULTS: The reasons for milk avoidance were intolerance (40%), bad taste (42%), and lifestyle choice (18%). Dietary calcium intakes were low (443 +/- 230 mg Ca/d), and few children consumed substitute calcium-rich drinks or mineral supplements. Although 9 children (18%) were obese, the milk avoiders were shorter (P < 0.01), had smaller skeletons (P < 0.01), had a lower total-body bone mineral content (P < 0.01), and had lower z scores (P < 0.05) for areal bone mineral density at the femoral neck, hip trochanter, lumbar spine, ultradistal radius, and 33% radius than did control children of the same age and sex from the same community. The z scores for volumetric (size-adjusted) bone mineral density (g/cm(3)) were -0.72 +/- 1.17 for the lumbar spine and -0.72 +/- 1.35 for the 33% radius (P < 0.001). Twelve children (24%) had previously broken bones. CONCLUSIONS: In growing children, long-term avoidance of cow milk is associated with small stature and poor bone health. This is a major concern that warrants further study.

Body fat percentages measured by dual-energy X-ray absorptiometry corresponding to recently recommended body mass index cutoffs for overweight and obesity in children and adolescents aged 3-18 y.

BACKGROUND: Body mass index (BMI; in kg/m2) cutoffs for use with children and adolescents aged 2-18 y that correspond to the well-accepted BMI cutoffs for overweight (> or = 25 but < 30) and obesity (> or = 30) in adults were published recently. OBJECTIVE: The objective was to estimate the percentage body fat (%BF) values typically associated with these BMI cutoffs in children and adolescents. DESIGN: The %BF was measured by dual-energy X-ray absorptiometry in 661 subjects (49% male) aged 3-18 y. Regression equations using BMI, age, and sex were developed to predict the %BF associated with BMI cutoffs for overweight (age-specific BMI equivalent to a BMI of 25 in an 18-y-old) and obesity (age-specific BMI equivalent to a BMI of 30 in an 18-y-old) over this age range. RESULTS: Measurements classified 17.1% of males and 19.8% of females as overweight and 5.5% of males and 7.5% of females as obese. The %BF associated with an obese BMI tended to be higher in peripubertal males (34-36%) than in younger (24-30%) or older (27-30%) males. Although the predicted %BF of young females was similar to that of young males, values rose steadily with age, such that an 18-y-old female with a BMI of 30 had an estimated %BF of 42%, whereas that in males of similar age was 27%. CONCLUSION: The %BF values associated with BMI classifications of overweight and obesity vary considerably with age in growing children, particularly in girls.

Validity of body mass index compared with other body-composition screening indexes for the assessment of body fatness in children and adolescents.

BACKGROUND: Validation studies of height- and weight-based indexes of body fatness in children and adolescents have examined only small samples of school-age children. OBJECTIVE: The objective was to validate the performance of age- and sex-specific body mass index (BMI) compared with the Rohrer index (RI) and weight-for-height in screening for both underweight and overweight in children aged 2-19 y. DESIGN: Data from the third National Health and Nutrition Examination Survey (n = 11096) and a pooled data set from 3 studies that used dual-energy X-ray absorptiometry (n = 920) were examined. The receiver operating characteristic curve was used to characterize the sensitivity and specificity of these 3 indexes in classifying both underweight and overweight. Percentage body fat and total fat mass were determined by dual-energy X-ray absorptiometry. Subcutaneous fat was assessed on the basis of the average of triceps and subscapular skinfold thicknesses. RESULTS: For children aged 2-19 y, BMI-for-age was significantly better than were weight-for-height and RI-for-age in detecting overweight when average skinfold thicknesses were used as the standard, but no differences were found in detecting underweight. When percentage body fat or total fat mass was used as the standard, BMI-for-age was significantly better than was RI-for-age in detecting overweight in children aged 3-19 y. No differences were found between BMI-for-age and weight-for-height in detecting overweight or underweight. CONCLUSION: For children and adolescents aged 2-19 y, the performance of BMI-for-age is better than that of RI-for-age in predicting underweight and overweight but is similar to that of weight-for-height.

Factor analysis of the metabolic syndrome in spinal cord-injured men.

Disturbances of carbohydrate and lipid metabolism in men with spinal cord injury are common, but poorly defined. Clustering of recognized risk factors for obesity and disorders of carbohydrate and lipid metabolism are characteristic of the metabolic syndrome. The purpose of this study was to investigate the presence of metabolic syndrome using modifications of the World Health Organization (WHO) definition and including total physical activity levels (minutes/week), in a group of active males with spinal cord injury who were carefully matched for age, height, and weight with active able-bodied males. Factor analysis is used widely to explore factors of the metabolic syndrome. This technique was used in this study of 20 spinal cord-injured (SCI) men and 20 able-bodied controls, matched for age, height, and weight. Three-factor models, each reflecting a different aspect of the metabolic syndrome, were identified for both study groups. The average communality score for the SCI group was 0.8 and 0.7 for the control group. For the SCI group, factor 1 reflected an interaction between adiposity measures, physical activity, and postload insulin and glucose, factor 2 was reflective of dyslipidemia, while factor 3 revealed an interaction between fasting levels of insulin and glucose. In the control group, factor 1 reflected an association between the adiposity measures and physical activity, factor 2 was reflective of postload glycemic control, with factor 3 reflecting an interaction between fasting insulin and dyslipidemia. By summation of the total variance of each factor, the 3-factor models explained 80% and 69% of the variance in the original 9 variables examined in the SCI and control groups, respectively. In summary, while the WHO definition for the metabolic syndrome appears suitable for use in identifying the incidence of this syndrome in SCI men, some modification of anthropometric and lipid measures may be required.

Children who avoid drinking cow's milk are at increased risk for prepubertal bone fractures.

The full fracture histories of 50 children (30 girls and 20 boys, age range 3 to 13 years) who had avoided drinking cow's milk for prolonged periods were compared with those in a birth cohort of more than 1,000 children from the same city. Children who avoided milk did not use calcium-rich food substitutes appropriately and had low dietary calcium intakes and low bone mineral density values. Many were overweight (22 of 50). Significantly more of the children who avoided milk reported fractures (16 observed vs 6 expected, chi(2)=31.0, P<.001, df=5). They also experienced more total fractures than the birth cohort population (22 observed vs 8 expected, chi(2)=33.6, P<.001, df=5). All of the fractures occurred before puberty, the majority (18 of 22) being associated with only slight trauma. Forearm fractures were especially common (12 fractures). We conclude that young children avoiding milk are prone to fracture.

Predictive ability of waist-to-height in relation to adiposity in children is not improved with age and sex-specific values.

A waist-to-height ratio (WHtR) ≥0.5 indicates increased health risk in children and adults. However, because of residual correlation between WHtR and height in children, dividing waist circumference by height to the power of one may be insufficient to correctly adjust for height during growth. This study aimed to determine whether age and sex-specific exponents which properly adjust for height affect the predictive ability of WHtR to correctly discriminate between children with differing fat distribution. Total and regional body fat was measured by dual-energy X-ray absorptiometry (DXA) in 778 (49% male) children and adolescents. WHtR was calculated as waist/height(1) (WHtR(a)), and using two published age and sex-specific exponents for height (WHtR(b)) (1) (WHtR(c)) (2), and compared with various DXA indexes of body composition using receiver operating curve analysis. 15% of males and 17% of females had a WHtR(a) ≥0.5, with corresponding figures of 8% and 27% for WHtR(b), and 23% and 17% for WHtR(c). WHtR(a) was significantly different from WHtR(b) (males only, P < 0.001) but not WHtR(c) (P = 0.121). Areas under the receiver operating curve (AUC) for WHtR(a) were significantly higher than AUCs for WHtR(b) or WHtR(c) in relation to DXA-measured body composition (AUCs ≥0.89 for WHtR(a) compared with AUCs of 0.71-0.84 for WHtR(b) and WHtR(c)). Simply dividing waist circumference by height (WHtR(a)) correctly discriminates between children and adolescents with low and high levels of total and central fat at least 90% of the time. Keeping your waist circumference to less than half your height provides an effective screening index of body composition during growth.

Changes in fat mass and fat-free mass during the adiposity rebound: FLAME study.

OBJECTIVE: To determine the changes in body composition from 3 to 7 years of age in children undergoing adiposity rebound (AR) at different ages. METHODS: Body composition was measured bi-annually by bioelectrical impedance in 229 children from a birth cohort. Age at AR was calculated from changes in weight and height velocity over time. Early AR was defined as < 6.1 years (boys) and < 5.6 years (girls). Differences in fat mass (FM) and fat-free mass (FFM) and the velocity of change in these measures were calculated between early and late rebounders. Physical activity (accelerometry), time in sedentary activity, birth factors, and parental weight were compared. RESULTS: Children with early and late AR did not differ in body composition at 3 years of age, except for greater FFM in boys (by 0.8 kg, P = 0.022). In both sexes, change in body mass index (BMI) was significantly higher in early compared with late AR, and was entirely due to differences in the rate of weight gain, rather than any discrepancy in height velocity. This weight differential is predominantly due to increased deposition of FM in girls and FFM in boys. However, in both sexes, children with early rebound have significantly greater increases in FM velocity from 5 years of age. Few differences in any environmental influences were observed. CONCLUSIONS: Variation in BMI associated with the timing of AR is due to differences in weight rather than height, and sex differences in the relative contribution of FM and FFM to this additional weight gain are apparent.

Sex differences in regional body fat distribution from pre- to postpuberty.

Few large studies have evaluated the emergence of sexual dimorphism in fat distribution with appropriate adjustment for total body composition. The objective of this study was to determine the timing and magnitude of sex differences in regional adiposity from early childhood to young adulthood. Regional fat distribution was measured using dual-energy X-ray absorptiometry (trunk and extremity fat using automatic default regions and waist and hip fat using manual analysis) in 1,009 predominantly white participants aged 5-29 years. Subjects were divided into pre (Tanner stage 1), early (Tanner stages 2-3), late (Tanner stages 4-5), and post (males > or =20 years and females > or =18 years) pubertal groups. Sexual dimorphism in trunk fat (adjusted for extremity fat) was not apparent until late puberty, when females exhibited 17% less (P < 0.001) trunk fat than males. By contrast, sex differences in waist fat (adjusted for hip fat) were apparent at each stage of puberty, the effect being magnified with age, with prepubertal girls having 5% less (P = 0.027) and adult women having 48% less (P < 0.0001) waist fat than males. Girls had considerably more peripheral fat whether measured as extremity or hip fat at each stage. Sex differences in regional adiposity were significantly greater in young adults than in late adolescence. Exclusion of overweight participants did not materially affect the estimates. Sexual dimorphism in fat patterning is apparent even prepubertally with girls having less waist and more hip fat than boys. The magnitude of the sex difference is amplified with maturation, and particularly from late puberty to early adulthood.

Patterns of growth associated with the timing of adiposity rebound.

This study was undertaken to evaluate the effects of age of adiposity rebound (AR) on measures of fat mass between ages 7 and 11 years, maturity, and adiposity in 458 children from a birth cohort studied to age 26 years. Patterns of growth between ages 3 and 26 years and changes in fat mass index between 7 and 11 years in groups with early (<5.5 years for boys and <5 years for girls), average (between 5.5 and 7.5 years for boys and between 5 and 7 years for girls), and late AR (> or =7.5 years for boys and > or =7 years for girls) are described. The mean z-scores for BMI, height, and weight increased between age 3 years and adolescence in the early-rebound group and decreased in the late-rebound group. The differences were maintained until adulthood for BMI and weight. Disproportionately high increases in fat mass index during growth (7-11 years), more advanced bone age in boys at age 7 years, and earlier menarche in girls were evident in the early-rebound group. The relative risks at 26 years of being overweight (BMI 25-29.9 kg/m(2)) and obese (BMI > or =30 kg/m(2)) were 2.70 (95% confidence interval (CI): 1.55, 4.66) and 5.91 (95% CI: 3.03, 11.55) respectively, using the average group as the reference. The corresponding relative risks for adult waist girths exceeding international cut points were 2.12 (95% CI: 1.09, 4.13) and 3.32 (95% CI: 1.46, 7.54). Thus, early rebound is associated with increased depositions of fat in middle childhood, and risks associated with early rebound persist at least until early adulthood.

Relationships of appendicular LMI and total body LMI to bone mass and physical activity levels in a birth cohort of New Zealand five-year olds.

The present study was undertaken to determine whether children with lower bone mass display lower muscle mass for their height than those with high bone mineral content (BMC) and whether appendicular lean mass (bone-free lean mass in arms plus legs) is associated with physical activity and/or BMC in preschool children. 158 children (59% male) from a New Zealand cohort born in 2001-2002 were studied close to their fifth birthday. Body composition was measured by dual energy X-ray absorptiometry (Lunar DPX-L). Lean mass index (LMI) was calculated as lean mass (kg) divided by height in metres squared. Physical activity was assessed objectively by accelerometry (Actical Mini-Mitter). Girls and boys had similar heights, weights and daily accelerometry counts but boys had lower fat mass, and higher lean mass and total body BMC than the girls (P<0.00l). In both sexes children with greater quantities of total and regional lean mass and higher LMI values had significantly higher bone mass. Appendicular LMI was more strongly associated with BMC than LMI. Accelerometry counts showed no associations with height but were positively associated with lean mass (r=0.23, P<0.03), appendicular LMI (r=0.25 P<0.01), total body BMC (r=0.24, P<0.02) and total body less head BMC (r=0.27 P<0.009) in the boys, but not in the girls. Greater time spent in more intense physical activity was also associated with higher appendicular lean mass and TBLH BMC only in the boys. We conclude that children with lower BMC values display not only lower lean mass but also lower total and appendicular lean mass for their height, than those with higher BMC values. The sex differences in associations of accelerometry counts to lean mass and BMC have been noted by others and require further investigation.

Relationship of total body fat mass to bone area in New Zealand five-year-olds.

Fat mass was recently shown to be a positive determinant of bone mass and size independently of lean mass in a birth cohort of British 9-year-olds. The present study was undertaken to investigate whether similar relationships are evident in younger, preschool children. Height and weight were measured, and a total-body dual-energy X-ray absorptiometric scan was performed on 194 preschool New Zealand children (81 girls, 113 boys) participating in the Dunedin birth cohort Family, Lifestyle, Activity, Movement, and Eating (FLAME) study close to their fifth birthday. Relationships of total-body fat mass and lean mass to total-body-less-head (TBLH) bone area and TBLH bone mineral content (BMC) were evaluated using linear regression. Girls had higher mean fat mass (3.9 vs. 3.2 kg) and lower lean mass (14.5 vs. 15.2 kg) than boys (P < 0.001), but their heights, weights, and TBLH bone area were similar. Although a given weight of lean tissue was associated with greater increases in TBLH area than a given weight of fat tissue, our results show that fat mass was an independent predictor of TBLH bone area (R (2 )= 0.79, P < 0.001) and TBLH BMC (R (2) = 0.74, P < 0.001) in data adjusted for socioeconomic status, ethnic group, lean mass, and height. We conclude that increased fat mass is associated with outward expansion of the TBLH skeletal envelope (wider bones) independently of height and lean mass in very young children.

Waist circumference as a measure of trunk fat mass in children aged 3 to 5 years.

OBJECTIVE: The increasing prevalence of obesity in young children emphasises the need for accurate measures of total and regional fat at this age. Thus the aim of this study was to evaluate the ability of waist circumference, waist-to-height ratio (WHtR) and the conicity index (CI) to discriminate between children with low and high levels of trunk fat mass. METHODS: Trunk fat mass was measured by dual-energy x-ray absorptiometry (DXA) in 301 predominantly Caucasian children (150 girls) aged 3-5 years. High trunk fat was defined as an internal z-score of > or =+1. Receiver-operating characteristic (ROC) curves and the areas under each curve (AUC) were constructed to compare the relative ability of waist circumference, WHtR and CI to identify children with low and high trunk fat mass. RESULTS: Girls had more truncal fat than boys (P<0.001). AUCs indicated that waist circumference correctly discriminated between children with low and high trunk fat mass 87% (for girls) to 90% (for boys) of the time. Waist circumference performed better than WHtR (AUCs: 0.79 in girls and 0.81 in boys; P=0.164 and P=0.011, respectively) and the CI (AUCs: 0.53 in girls and 0.65 in boys, P<0.0001). A z-score of 0.55 correctly identified 79% of girls and 81% of boys with high trunk fat mass, and 82% of girls and 84% of boys with low trunk fat mass. Suggested waist circumference cut-offs for each half-year of age in both sexes are reported. CONCLUSION: Waist circumference performs reasonably well as an indicator of high trunk fat mass in preschool-aged children.