Body composition through adult life: Swedish reference data on body composition.

BACKGROUND/OBJECTIVES: The prevalence of obesity, defined as body mass index (BMI) ⩾30 kg/m(2), differs between populations; however, there is a need for data on description on body composition in reference populations of different ages and from different countries. The objective of this study was to pool dual-energy X-ray absorptiometry (DXA) body composition reference data from population-based Swedish cohorts. SUBJECTS/METHODS: Four population-based cross-sectional cohort studies including 1424 adult Swedes were divided into five age groups (20-29, 30-39, 40-49, 50-61 and 75 years of age); BMI 24.6±3.9 kg/m(2) were pooled. Body composition was measured with DXA. RESULTS: The difference in BMI from the youngest to the oldest age group was 3.2 and 4.3 kg/m(2) in men and women, respectively (P<0.001, both sexes), and fat mass (FM) was 9.9 and 9.1% higher in the oldest compared with the youngest men and women (P<0.001, both sexes). Fat-free mass (FFM) remained stable up to 60 years of age in men (P=0.83) and was lower at 75 years of age compared with the younger ages. In women, FFM was lower from age 60. From youngest to oldest age groups, height-adjusted FM differed from 4.6 to 7.8 kg/m(2) in men and from 6.8 to 10.8 kg/m(2) in women (P<0.001, both sexes). CONCLUSIONS: Our results provide reference data on body composition in Swedish populations. BMI and FM were higher among older age groups compared with the younger ones. FFM remained stable up to 60 years of age and was lower first among the 75 years of age.

Body composition in a cohort of Swedish adolescents aged 15, 17 and 20.5 years.

OBJECTIVE: To assess variables of body composition and identify their correlates in a group of individuals studied from adolescence to early adulthood. METHODS: Cross-sectional results were obtained from 203, 149 and 106 subjects at the respective ages. Sixty-two subjects examined at all three ages constituted the longitudinal study group. A cohort of randomly selected 15-year-old adolescents from an industrial town in Sweden was studied by dual energy X-ray absorptiometry (DXA) and followed up at 17 and 20.5 years. Lean body mass (LBM), fat mass (FM) and total body bone mineral content (TBMC) were measured by DXA. Total bone mineral density (TBMD) was calculated. Information of parental educational level, energy intake and food habits, energy expenditure (TEE) and physical activity level (PAL) was obtained by questionnaires and diaries. RESULTS: LBM, TBMC and TBMD increased significantly more in males and FM more in females, from 15 to 20.5 years of age. Body weight, height, TEE, PAL and the fathers' educational level and, at age 15, also gender were identified as significant correlates of the body composition variables. CONCLUSION: New reference values for body composition at ages 15, 17 and 20.5 years are presented and also a finding about an association between the father's educational level and the adolescent's body composition.

Elevated serum levels of estradiol, dihydrotestosterone, and inhibin B in adult males born small for gestational age.

CONTEXT: Prenatal growth restriction may affect future fertility in both females and males. Studies have shown that growth-retarded male rats have different sexual behavior and disturbed steroidogenesis. OBJECTIVE: We hypothesized that adult human males born small for gestational age (SGA) have an altered sex hormone profile. DESIGN, SETTING, AND PATIENTS: Twenty-five adult males born SGA with median birth weight -2.2 sd scores (SDS) and birth length -2.4 SDS were studied. Median age was 23.1 yr and final height -0.5 SDS. They were compared with 44 male controls with median age 20.5 yr and final height 0.4 SDS. MAIN OUTCOME MEASURE: The primary outcome before the study started was 17beta-estradiol (E(2)) levels in SGA males. RESULTS: The SGA group showed significantly higher median levels of E(2), 17.9 pg/ml (P < 0.001), and dihydrotestosterone (DHT), 0.543 ng/ml (P < 0.05), compared with controls, 12.6 pg/ml and 0.423 ng/ml, respectively. Testosterone (T) levels did not differ between groups. E(2) to T ratio correlated negatively to birth weight (r = -0.40, P < 0.01) and birth length (r = -0.44, P < 0.001). DHT to T ratio correlated negatively to birth weight (r = -0.51, P < 0.001) and birth length (r = -0.38, P < 0.01). Males born SGA also had significantly higher median levels of inhibin B, 164 pg/ml (P < 0.05), compared with controls, 137 pg/ml. Inhibin B correlated negatively to birth length (r = -0.34, P < 0.01). CONCLUSION: SGA males of normal stature have higher levels of E(2), DHT, and inhibin B than controls, indicating a disturbed steroid synthesis or metabolism. Aromatase activity, calculated as E(2) to T ratio, and 5alpha-reductase activity, calculated as DHT to T ratio, is negatively correlated to size at birth.

Bone mineral density and bone turnover in young adult survivors of childhood acute lymphoblastic leukaemia.

OBJECTIVE: Treatment for childhood leukaemia induces many risk factors for development of decreased bone mineral density (BMD). Physical activity is also known to affect BMD. The aim was to study BMD and markers of bone turnover in a well-defined group of survivors of acute lymphoblastic leukaemia (ALL) who had all reached final height as well as peak bone mass, taking both previous treatment and physical activity into consideration. DESIGN: All patients treated for ALL before the onset of puberty in the region of western Sweden, between 1973 and 1985, in first remission were included. Thirty-five out of forty-seven patients aged 20-32 years participated. Nineteen patients had received cranial radiotherapy, and the median follow-up time was 20 years. METHODS: BMD was assessed using dual-energy X-ray absorptiometry (DEXA). Serum concentrations of markers of bone turnover were analysed. Physical performance was measured using a performance exercise capacity stress test. RESULTS: BMD was slightly reduced in lumbar spine (-0.4 SD), but not in femoral neck or total body. BMD in femoral neck was correlated to physical performance and dose of corticosteroid, but no correlation was found with spontaneous growth hormone (GH) secretion. Markers of bone turnover were also correlated to physical performance, but not to GH secretion. CONCLUSIONS: Physical fitness seems to be the most important factor in developing and preserving normal bone mineral density in ALL patients. We propose that lifestyle education promoting physical activity is encouraged from an early point in time for these patients.

Body composition, as assessed by bioelectrical impedance spectroscopy and dual-energy X-ray absorptiometry, in a healthy paediatric population.

UNLABELLED: The aim of this study was to determine the level of agreement between body composition measurements by dual-energy X-ray absorptiometry (DXA), single-frequency bioelectrical impedance analysis (BIA) and multifrequency bioelectrical impedance spectroscopy (BIS). Fat-free mass (FFM), body fat mass and body fatness (percentage fat) were measured by DXA, BIA and BIS in 61 healthy children (37M, 24F, aged 10.9-13.9 y). Estimates of FFM, body fat mass and body fatness were highly correlated (r = 0.73-0.96, p < 0.0001) between the different methods. However, a Bland-Altman comparison showed wide limits of agreement between the methods. The mean differences between methods for FFM ranged from -2.31 +/- 7.76 kg to 0.48 +/- 7.58 kg. Mean differences for body fat mass ranged from 0.16 +/- 5.06 kg to 2.95 +/- 5.65 kg and for body fatness from -2.3 +/- 7.8% to 0.8 +/- 9.3%. Calculations of body composition with BIS were not superior to BIA. However, BIA overestimated fat mass in lean, subjects and underestimated fat mass in overweight subjects more than BIS, compared with DXA. CONCLUSION: The methods used provided estimates of FFM, body fat mass and body fatness that were highly correlated in a population of healthy children. However, the large limits of agreement derived from the Bland-Altman procedure suggest that the methods should not be used interchangeably.

Currently used growth-promoting treatment of children results in normal bone mass and density. A prospective trial of discontinuing growth hormone treatment in adolescents.

BACKGROUND AND AIMS: The need for continued GH replacement in patients with childhood-onset GH deficiency (GHD) into adulthood has been recognized. The consequences of discontinuing GH treatment on bone mineralization in adolescent patients with GHD and short stature were examined over a period of 2 years. PATIENTS: Forty adolescents (aged 16-21 years) treated with GH for more than 3 years and 16 closely matched healthy controls were studied. After a baseline visit, GH treatment was discontinued. The patients were then re-examined with the same protocol after 1 and 2 years. Twenty-one patients had continuing severe GHD into adulthood, while 19 patients were regarded as having sufficient endogenous GH secretion (GHS). RESULTS: At baseline, there were no differences between the groups in total bone mineral content (BMC) or bone mineral density (BMD). After 2 years without GH treatment, BMC increased similarly in the GHD and GHS groups. BMC of the lumbar spine (L2-L4) increased only in the GHD group. Lumbar spine BMD increased in the GHD and the GHS groups. No changes were observed in the femoral neck region. Biochemical measurements showed that carboxy-terminal cross-linked telopeptide of type I collagen (ICTP) and bone specific alkaline phosphates (ALP) were higher in the GHD and GHS groups at baseline compared with controls. Osteocalcin, carboxy-terminal propeptide of type I procollagen (PICP), ICTP and ALP decreased during the 2 years off treatment in both the GHD and GHS groups. PICP was also lower after 2 years in the GHD group compared with both the GHS group and controls. CONCLUSIONS: After discontinuation of GH therapy in adolescents at or near final height, there was a continued increase in BMC and BMD both for adolescents with growth hormone deficiency and for those classified as growth hormone sufficient. These groups did not differ from controls at baseline or after 2 years. In the growth hormone deficiency group, biochemical markers for bone formation decreased to levels below those in the growth hormone sufficient and healthy control groups. Although the number of patients and controls in this study were small, the results indicate that the present treatment of Swedish GH-deficient children to final height results in normal BMD.

Serum leptin levels correlate with growth hormone secretion and body fat in children.

The aim of this study was to investigate the relationship among GH secretion, leptin concentrations, and body composition measured with x-ray absorptiometry (DXA) in children. In total, 71 children were investigated, 51 males and 20 females. Their mean chronological age was 10.8 yr (range, 6.2-17.7 ys), and their mean height (SD) was -2.1 (0.63) SD scores. Their mean weight for height SD scores (WH(SDS)) was 0.2 (1.18). Body composition was investigated using DXA. Blood samples were taken for analysis of leptin, insulin-like growth factor I (IGF-I), IGF-binding protein-3, and 24-h GH secretion. A positive correlation was found between leptin and total body fat (r = 0.83; P < 0.0001) and when fat was expressed as a percentage of body weight (r = 0.86; P < 0.0001). There were significant (P < 0.0001) relationships between leptin and WH(SDS) (r = 0.45) and between leptin and body mass index (r = 0.69). A significant gender difference in leptin levels was found, but this disappeared after adjustment for body fat, as measured by DXA. There were significant (P < 0.001) inverse correlations between leptin and the AUCb for GH (r = -0.41), leptin, and GHmax (r = -0.38), where AUCb is the area under the curve above the calculated baseline, and GHmax is the maximum peak during the 24-h GH profile (percent fat and AUCb for GH, r = -0.43; percent fat and GHmax, r = -0.39). In a multiple stepwise forward regression analysis with leptin as the dependent variable, the percent trunk fat accounted for 77.7% of the leptin variation. With AUCb for GH as the dependent variable, the percent trunk fat accounted for 20.3% of the variation. With GHmax as the dependent variable, the percent trunk fat accounted for 18.8% of the variation, IGF-binding protein-3 for another 8.5%, and the percentage of fat from arms and legs for another 4.4%. We demonstrated a strong positive correlation between leptin levels and body fat, a significant negative correlation between leptin levels and GH secretion, and a significant negative correlation between body fat and GH secretion. We have also shown that specific regional fat depots have different relationships with leptin and particular markers of GH secretion.

Changes in body composition and leptin levels during growth hormone (GH) treatment in short children with various GH secretory capacities.

OBJECTIVE: The aim of this study was to follow changes in body composition, estimated by dual-energy X-ray absorptiometry (DXA), in relation to changes in leptin during the first year of GH therapy in order to test the hypothesis that leptin is a metabolic signal involved in the regulation of GH secretion in children. DESIGN AND METHODS: In total, 33 prepubertal children were investigated. Their mean (S.D.) chronological age at the start of GH treatment was 11.5 (1.6) years, and their mean height was -2.33 (0.38) S.D. scores (SDS). GH was administered subcutaneously at a daily dose of 0.1 (n=26) or 0.2 (n=7) IU/kg body weight. Ten children were in the Swedish National Registry for children with GH deficiency, and twenty-three children were involved in trials of GH treatment for idiopathic short stature. Spontaneous 24-h GH secretion was studied in 32 of the children. In the 24-h GH profiles, the maximum level of GH was determined and the secretion rate estimated by deconvolution analysis (GHt). Serum leptin levels were measured at the start of GH treatment and after 10 and 30 days and 3, 6 and 12 months of treatment. Body composition measurements, by DXA, were performed at baseline and 12 months after the onset of GH treatment. RESULTS: After 12 months of GH treatment, mean height increased from -2.33 to -1.73 SDS and total body fat decreased significantly by 3.0 (3.3)%. Serum leptin levels were decreased significantly at all time points studied compared with baseline. There was a significant correlation between the change in total body fat and the change in serum leptin levels during the 12 months of GH treatment, whereas the leptin concentration per unit fat mass did not change. In a multiple stepwise linear regression analysis with 12 month change in leptin levels as the dependent variable, the percentage change in fat over 12 months, the baseline fat mass (%) of body mass and GHt accounted for 24.0%, 11.5% and 12.2% of the variability respectively. CONCLUSIONS: There are significant correlations between changes in leptin and fat and endogenous GH secretion in short children with various GH secretory capacities. Leptin may be the messenger by which the adipose tissue affects hypothalamic regulation of GH secretion.