Bone status measured by quantitative ultrasound: a comparison with DXA in Thai children.

BACKGROUND/OBJECTIVES: Quantitative ultrasound (QUS) is used to measure bone quality and is known to be safe, radiation free and relatively inexpensive compared with dual-energy X-ray absorptiometry (DXA) that is considered the gold standard for bone status assessments. However, there is no consensus regarding the validity of QUS for measuring bone status. The aim of this study was to compare QUS and DXA in assessing bone status in Thai children. SUBJECTS/METHODS: A total of 181 Thai children (90 boys and 91 girls) aged 6 to 12 years were recruited. Bone status was measured by two different techniques in terms of the speed of sound (SOS) using QUS and bone mineral density (BMD) using DXA. Calcium intake was assessed by 24 h diet recall. Pearson's correlation, κ-statistic and Bland and Altman analysis were used to assess the agreement between the methods. RESULTS: There was no correlation between the two different techniques. Mean difference (s.d.) of the Z-scores of BMD and SOS was -0.61 (1.27) that was different from zero (P<0.05). Tertiles of Z-scores of BMD and QUS showed low agreement (κ 0.022, P=0.677) and the limits of agreement in Bland and Altman statistics were wide. CONCLUSIONS: Although QUS is easy and convenient to use, the SOS measurements at the radius seem not appropriate for assessing bone quality status.

Using dilution techniques and multifrequency bioelectrical impedance to assess both total body water and extracellular water at baseline and during recombinant human growth hormone (GH) treatment in GH-deficient adults.

Due to the use of various, and mostly indirect, methods to estimate total body water (TBW) and extracellular water (ECW), there is no agreement about whether body water distribution, i.e. the ECW to TBW ratio, is normal in GH-deficient (GHD) subjects at baseline and during recombinant human GH (rhGH) treatment. We studied body water distribution in 14 patients with adult-onset GHD and in 28 healthy controls. We also investigated the effect of GH replacement therapy for 4 and 52 weeks on body water distribution. All patients started with a dose of 0.6 IU rhGH/day for the first 4 weeks. After 52 weeks, the dose varied between 0.6-1.8 IU/day. TBW and ECW were measured by dilution of deuterium and bromide, respectively. Both parameters were also estimated using multifrequency bioelectrical impedance (BIA). Patients with GHD had significantly lower ECW and TBW than healthy controls. In addition, the ECW to TBW ratio was significantly lower in GHD patients than in healthy controls. Four weeks of GH treatment significantly increased body weight, TBW, ECW, and ECW/TBW. A further increase in TBW, but not ECW, was found after 52 weeks of treatment. The mean increases in TBW and ECW from the baselines were 2.5 +/- 0.3 and 2.0 +/- 0.3 L, respectively. The correlation coefficient and the estimated reliability between measured and estimated TBW and ECW at any time point were all high (> 0.91 and > 0.95, respectively). In general, both ECW and TBW were overestimated by multifrequency BIA in GHD adults. During treatment, the overestimation of both ECW and TBW diminished. The estimation error was correlated with the level of the body water compartment and the ratio of ECW to TBW. The estimated change in ECW with rhGH treatment was underestimated by multifrequency BIA. We conclude that GHD adults have lower ECW and TBW and a lower ECW to TBW ratio, as measured by dilution techniques. The ECW to TBW ratio can be normalized within 4 weeks of rhGH treatment at a dose of 0.6 IU/day. Finally, we conclude that multifrequency impedance measurements do not give valid estimates of body water compartments in the follow-up of patients with GHD.

Visceral fat accumulation in relation to sex hormones in obese men and women undergoing weight loss therapy.

In 70 healthy obese subjects (37 men and 33 premenopausal women; aged 27-51 yr; body mass index, 28-38 kg/m2), associations between the initial amount of visceral fat and sex hormone levels were studied as well as between changes that occurred in response to a 4.2 mJ/day deficit diet for 13 weeks. Magnetic resonance imaging was used to quantify the visceral fat depot. In women, an abundance of visceral fat was significantly associated with diminished levels of sex hormone-binding globulin and free 17 beta-estradiol/free testosterone (T) ratio and to elevated levels of free T after adjustment for age and total fat mass. In men, no significant relationships could be found between visceral fat accumulation and any of the sex hormones. Mean total fat loss was 11.3 +/- 3.3 (+/- SD) kg. In women, loss of visceral fat was significantly related to rises in the sex hormone-binding globulin level and the free 17 beta-estradiol/free T ratio independent of total fat loss, whereas in men, only the association between visceral fat loss and increased estrone level reached statistical significance. In conclusion, in obese premenopausal women, visceral fat predominance seems to be related to a relatively increased androgenicity. In obese men, sex steroid levels appear not to depend on the amount of visceral fat. In obese women, but not in obese men, visceral fat loss seems to be accompanied by a relative reduction in androgenicity.

Asians are different from Caucasians and from each other in their body mass index/body fat per cent relationship.

The objective was to study the relationship between body mass index (BMI) and body fat per cent (BF%) in different population groups of Asians. The study design was a literature overview with special attention to recent Asian data. Specific information is provided on Indonesians (Malays and Chinese ancestry), Singaporean Chinese, Malays and Indians, and Hong Kong Chinese. The BMI was calculated from weight and height and the BF% was determined by deuterium oxide dilution, a chemical-for-compartment model, or dual-energy X-ray absorptiometry. All Asian populations studied had a higher BF% at a lower BMI compared to Caucasians. Generally, for the same BMI their BF% was 3-5% points higher compared to Caucasians. For the same BF% their BMI was 3-4 units lower compared to Caucasians. The high BF% at low BMI can be partly explained by differences in body build, i.e. differences in trunk-to-leg-length ratio and differences in slenderness. Differences in muscularity may also contribute to the different BF%/BMI relationship. Hence, the relationship between BF% and BMI is ethnic-specific. For comparisons of obesity prevalence between ethnic groups, universal BMI cut-off points are not appropriate.

Elevated body fat percentage and cardiovascular risks at low body mass index levels among Singaporean Chinese, Malays and Indians.

The aim of this study was to investigate the relationship between body mass index (BMI) and body fat percentage (BF%) in Singaporean Chinese, Malays and Indians, and to determine the risk for selected comorbidities at various BMI categories and abdominal fat distributions, as assessed by waist circumference (WC). The study was a cross-sectional (population) design. In total, 4723 subjects participated in the National Health Survey of 1998 in which the risks were investigated. A selected subsample of 291 subjects participated in a detailed body composition study, where weight, height and WC were measured, as were blood pressure, total and high-density lipoprotein (HDL) cholesterol, serum triglycerides and fasting glucose. In the subsample, BF% was determined by means of a chemical four-compartment model. At any given BF% the BMI of Singaporeans was about 3 kg m(-2) lower than that of Caucasians. There were slight differences in the BF%/BMI relationship between the three ethnic groups. For all the ethnic groups, it was found that at low categories of BMI (between 22 and 24 kg m(-2)) and WC (between 75 and 80cm for women and between 80 and 85 cm for men), the absolute risks for having at least one of the aforementioned risk factors were high, ranging from 41 to 81%. At these same categories the relative risks were significantly higher compared to the reference category, odds ratios ranging from 1.97-4.38. These categories of BMI and WC were all far below the cut-off values of BMI and WC as currently recommended by the World Health Organization (WHO). The data from the current study, which includes evidence that not only risk factors, but also BF% are elevated at low BMI values, presents a strong case for lowering the BMI cut-off value for overweight and obesity among Singaporeans, from 25 kg m(-2) and 30 kg m(-2) to 23 kg m(-2) and 27 kg m(-2), respectively.

Limitations of the bioelectrical impedance method for the assessment of body fat in severe obesity.

Bioelectrical impedance analysis enables a rapid and safe assessment of body water. When it is assumed that the hydration factor of the fat-free mass is constant and is not different in the obese state, then fat-free mass and thus body fat can be assessed with bioelectrical impedance. However, several factors limit the valid application of bioelectrical impedance analysis in the severely obese state. One is the assumption of a constant hydration factor. Furthermore, body geometry is different in the obese state and body water distribution may also be different. All these factors have an effect on the validity of the method in the severely obese state, for which the amount of body fat generally will be underestimated with use of prediction formulas developed in normal-weight subjects. I discuss these limiting factors and provide some theoretical background.

Body composition in children: proposal for a method for calculating body fat percentage from total body density or skinfold-thickness measurements.

A method is presented for assessing childhood obesity in a more objective way than most other routine methods used for diagnosing childhood obesity. The sum of bicipital, tricipital, subscapular, and suprailiacal skinfold thicknesses is related to total body density by use of theoretically defined prediction equations. Total body density is used to estimate total body fat percentage by use of age- and sex-dependent equations on the relation between body fat percentage and body density. These equations are constructed on the basis of published data on changes in the density of fat-free mass with age in children. With the proposed method childhood obesity can be assessed routinely in a more consistent way than with most other routine methods used to diagnose obesity in children. A preliminary validation study indicated that in children aged 7-10 y predicted body density differed on average less than 1% from measured body density. In addition, predicted body density was highly correlated (r greater than 0.7) with measured body density.

A critical evaluation of heart rate monitoring to assess energy expenditure in individuals.

The prediction of energy expenditure (EE) from minute-by-minute heart rate (HR) recording was evaluated in 40 female workers, with emphasis on the inter- and intraindividual variation of this method. The results show that the relationship between EE and HR varied greatly between and within subjects. The inter- and intraindividual CVs were 14-18% and 11-20%, respectively. The poor limits of agreement in EE (mean difference +/- 2 SD) between group and individual calibration curves indicate that estimated EE from group curves is inferior to estimated EE from individual curves. Therefore, it is concluded that to have the best estimates of individual EE, only individual calibration curves should be used. At different occasions these curves should be generated again. Because the limits of agreement in EE between individual curves based on 18 and 9 different activities were wide (-2399 to 1817 kJ/16 h), it is preferable to have a wide range of different activities in the individual calibration procedure.

Changes in fat-free mass during weight loss measured by bioelectrical impedance and by densitometry.

A group of 13 apparently healthy, premenopausal obese women (134-196% ideal weight) volunteered in a weight reduction study for 8 wk on a 4200 kJ (1000 kcal) diet. Before and after the weight reduction period body composition was measured by densitometry and by the bioelectrical impedance method. Changes in fat mass and fat-free mass were calculated. Mean weight loss was 10.0 +/- 2.8 kg and loss of fat-free mass was measured to be 2.3 +/- 1.7 kg (23%) by densitometry and 0.6 +/- 1.9 kg (6%) by impedance measurements. The underestimation of the change in fat-free mass measured by the impedance method could be due to losses of water bound to glycogen after the weight-reduction period. For this reason the impedance method may be not applicable in studies in which changes in glycogen stores can be expected.

Predicting body composition by densitometry from simple anthropometric measurements.

New equations have been developed to predict body fat (percent BF) calculated from body density measured by underwater weighing from simple anthropometric measurements, using stepwise-multiple-regression analysis in 63 men and 84 women. Log10 sum of four skinfold thickness explained 80.1% (SE = 3.8) of variance of percent BF in men and 76.4% (SE = 4.6) in women. Alternative equations using limb lengths instead of height may be valuable for epidemiologic and clinical work, with particular advantages for the chair- or bed bound, for whom no previous predictive equations existed. Five equations combining triceps-skinfold thickness with other anthropometric measurements explained > 80% (men) and 77% (women) of variance. The most powerful prediction was from waist circumference and triceps-skinfold thickness, which explained 86.6% (SE = 3.2) of variance of percent BF in men and 79.0% (SE = 4.0) in women. Percent BF for men = 0.353 waist (cm) + 0.756 triceps (mm) + 0.235 age (y) - 26.4; for women = 0.232 waist (cm) + 0.657 triceps (mm) + 0.215 age (y) - 5.5. The equations were tested in a separately studied validation sample of 146 men and 238 women aged 18-83 y. Skinfold-thickness measurements continued to give good predictions of mean body density, but with significant bias at extremes of body fat and age. The most robust prediction with the least bias was from waist circumference adjusted for age. Percent BF for men = 0.567 waist (cm) + 0.101 age (y) - 31.8; and for women = 0.439 waist (cm) + 0.221 age (y) - 9.4.

Resting metabolic rate and diet-induced thermogenesis in abdominal and gluteal-femoral obese women before and after weight reduction.

Fifteen premenopausal obese women, seven abdominal obese (AO) and eight gluteal-femoral obese (GFO), followed an energy-reduced diet of 1000 kcal/d (4.2 MJ/d) over 8 wk. Body-fat distribution was assessed using a cutoff point of 0.80 for the waist-to-hips girth ratio. Before and after the dietary treatment resting metabolic rate (RMR) and diet-induced thermogenesis (DIT) (after a normal breakfast) were measured by indirect calorimetry. Body-weight reduction and energy intake during the diet period did not differ significantly between both groups. Before weight loss the AO group had slightly greater RMR than the GFO group. After weight loss mean RMR decreased about 10% in the AO group and about 2.5% in the GFO group. Before weight loss DIT was slightly but not significantly higher in the AO group than in the GFO group. After weight loss DIT increased significantly in the GFO group. Weight loss was generally associated with decreased blood glucose, serum triglycerides, and total serum cholesterol levels in the AO women but not in the GFO women.

Fat distribution, androgens, and metabolism in nonobese women.

Eighty-five randomly selected women, all born in 1948, were studied. All were nonobese (body mass index [BMI], 23.3 +/- 0.3 (means +/- SD]). The relationships between three indicators of fat distribution (waist-hip, waist-thigh, and subscapular-triceps ratios) and hormonal and metabolic variables were studied. Increased androgenic activity (ratio of free testosterone [T] to total testosterone [free-total T ratio]) and degree of obesity (BMI) were independently related to increased waist-hip ratio. Waist-hip and waist-thigh ratios showed higher correlations with all metabolic variables than did the triceps-subscapular skinfold thickness ratio except for diastolic blood pressure. After adjustment for BMI and free-total T ratio, the waist-hip ratio was still significantly positively related to total cholesterol and C peptide and negatively to the HDL-total cholesterol ratio. In such multiple regression, BMI was independently related to insulin, C peptide, and diastolic blood pressure. The free-total T ratio was independently related to triglycerides. BMI and waist-hip ratio gave important complementary information about risk factors for diseases such as cardiovascular disease and diabetes mellitus.

Assessment of body composition by bioelectrical impedance in a population aged greater than 60 y.

Body composition was measured in a group of 35 healthy men and 37 healthy women aged 60-83 y. Body mass index (BMI) in men was 25.0 +/- 2.2 kg/m2 (means +/- SD) and in women, 25.9 +/- 3.2 kg/m2. BMI was low in relation to body fat percentage as determined by skinfold-thickness measurements or densitometry in comparison with the relation found in younger adults. Mean body fat percentage of the male subjects (aged 70.4 +/- 5.2 y) as determined by densitometry was 31.0 +/- 4.5%, whereas in women (aged 68.0 +/- 5.2 y) it was 43.9 +/- 4.3%. Body impedance correlated with fat-free mass (FFM). The best prediction formulas for the FFM from body impedance and anthropometric variables were 1) FFM (kg) = (0.671 x 10(4) x H2/R) + 3.1S + 3.9 where H is body height (m), R is resistance (omega), and S is gender (females, 0; males, 1) (r = 0.94; SEE = 3.1 kg) and 2) FFM (kg) = (0.360 x 10(4) x H2/R) + 0.359BW + 4.5S - 20T + 7.0 where BW is body weight (kg) and T is thigh circumference (m) (r = 0.96; SEE = 2.5 kg). The prediction equations from the literature, generally determined in younger populations, overestimated FFM in elderly subjects by approximately 6 kg and are not applicable to elderly subjects.

Body composition changes assessed by bioelectrical impedance measurements.

Twelve healthy volunteers consumed a very-low-calorie diet for 2 d to achieve a body-weight loss mainly from a loss of fat-free mass, ie, of glycogen plus water. Body weight, body density, and bioelectrical impedance were measured before and after weight loss. Body-weight loss was 1.3 +/- 0.5 kg. Loss of fat-free mass as measured by densitometry was 1.2 +/- 0.8 kg. Changes in body weight and fat-free mass measured by densitometry did not differ significantly and were significantly different from zero. Reduction of fat-free mass as determined by bioelectrical impedance was 0.5 +/- 0.8 kg, which was significantly different from body-weight loss and loss of fat-free mass as measured by densitometry but not significantly different from zero. The results show that after weight loss the bioelectrical impedance method overestimates the fat-free mass by approximately 1 kg.

Resting metabolic rate and diet-induced thermogenesis in young and elderly subjects: relationship with body composition, fat distribution, and physical activity level.

To investigate the relationship between age and energy expenditure, resting metabolic rate (RMR) and diet-induced thermogenesis (DIT; for 180 min after a 1.3-MJ meal) were measured by indirect calorimetry in 56 young and 103 elderly subjects. In addition, the influence of body composition, body-fat distribution, and physical activity level on this relationship was studied. RMR was significantly lower in elderly (3.98 +/- 0.46 and 3.33 +/- 0.39 kJ/min for men and women, respectively) than in young (5.29 +/- 0.53 and 4.08 +/- 0.33 kJ/min for men and women, respectively) subjects, which persisted after adjustment for body composition. DIT was significantly lower in older than in younger men (126 +/- 27 vs 154 +/- 34 kJ/180 min) but not in women (111 +/- 26 vs 115 +/- 25 kJ/180 min). The difference in men disappeared after adjustment for body composition. No clear relation between physical activity level and RMR or DIT was observed. These results demonstrate a relationship of age per se with RMR but not with DIT.

Energy expenditure at rest and during standardized activities: a comparison between elderly and middle-aged women.

To estimate energy expenditure (EE) in elderly subjects, more age-specific data are required on energy costs of standardized activities. EE was assessed by using indirect calorimetry in 28 women aged 72 +/- 4 y (mean +/- SD) and in 29 middle-aged women (42 +/- 1 y) at rest (resting metabolic rate; RMR) and during sitting, sitting with standardized arm activity, and walking on a treadmill at 3 km/h. RMR and EE during sitting, and sitting with standardized arm activity did not differ significantly between the groups, although EE expressed as a ratio of arm activity to RMR (physical activity ratio, PAR) tended to be higher in the elderly subjects. Walking EE was significantly higher in the elderly women (16.4 +/- 4.0 kJ/min) than in the middle-aged women (12.7 +/- 2.3 kJ/min), also when expressed as PAR. It is suggested that elderly women walk less efficiently. Because PARs are frequently used to estimate daily EE, it is important to note that additional age-specific data might be required.

Effect of a weight cycle on visceral fat accumulation.

Magnetic resonance imaging was used to study the effect of a single weight cycle on three fat depots: the visceral and subcutaneous abdominal depots and the subcutaneous depot at the trochanter level. Obese subjects (17 men, 15 women) were examined before and after weight-loss intervention and 67 wk after intervention. They lost 12.9 +/- 3.3 (mean +/- SD) kg body wt during intervention and regained 11.9 +/- 5.1 kg during follow-up. Weight regain did not result in greater body fatness than before weight loss (initial fat mass: 34.3 +/- 6.1 kg, final fat mass: 32.8 +/- 7.7 kg; P = 0.047). There was no indication of a preferential deposition of visceral fat after weight regain (initial visceral fat area: 120 +/- 41 cm2, final visceral fat area: 110 +/- 48 cm2; P = 0.087). On the contrary, there was a slight tendency to accumulate subcutaneous fat at the expense of visceral fat. It is concluded that weight loss followed by weight regain neither leads to a greater body fatness nor to a larger amount of visceral fat compared with before weight loss.

Body composition in growth hormone-deficient adults.

Body composition in a group of growth hormone (GH)-deficient adults was compared with a control group matched for age, sex, body height, body weight, and body mass index by using bioelectrical impedance and deuterium oxide-dilution methods and hydrodensitometry. The body-fat percentages of GH-deficient adults were higher despite comparable weight, height, age, and body mass index. Body impedance was higher in the GH-deficient adults after correction for differences in height and fat-free mass. As a consequence, prediction formulas for body composition from body impedance developed in normal subjects cannot be applied to GH-deficient subjects. The higher body impedance in the GH-deficient subjects can be ascribed to a smaller amount of extracellular water in these subjects than in control subjects.

Diurnal variation in postabsorptive resting metabolic rate and diet-induced thermogenesis.

Postabsorptive resting metabolic rate (RMR) and diet-induced thermogenesis (DIT) were repeatedly assessed on different days in 10 young men of normal weight on mornings and afternoons. No significant diurnal variation was found in RMR, DIT, total postprandial substrate oxidation, and overall postprandial nutrient balances. The pattern of postprandial substrate oxidation indicated an increased glucose oxidation in the first hour after ingestion of a meal on morning tests compared with afternoon tests. This was probably related to differences in the degree of the postabsorptive state, ie, 12-14 h on morning tests and 6-7 h on afternoon tests.

Limited effect of consumption of uncooked (RS2) or retrograded (RS3) resistant starch on putative risk factors for colon cancer in healthy men.

To investigate whether resistant starch (RS) affects putative risk factors for colon cancer, 24 healthy men consumed a daily RS supplement for 4 wk in addition to their habitual diet in a single-blind, randomized, balanced multiple crossover trial. During the first week, all subjects consumed the control supplement containing glucose. Subsequently, each subject consumed, in random order, a supplement with RS2 (uncooked high-amylose cornstarch), RS3 (extruded and retrograded high-amylose cornstarch), and glucose, each for 1 wk. The RS2 and RS3 supplements provided 32 g RS/d. Lithium was added to the supplements to measure compliance. Feces, 24-h urine, and breath samples, as well as a 24-h food-consumption recall were obtained weekly from each subject. Compliance as measured by urinary lithium recovery was satisfactory. The mean composition of the background diet did not differ between the various supplementation periods. Breath-hydrogen excretion, stool weight, and fecal starch excretion were significantly higher during RS than during glucose supplementation, but did not differ during RS2 and RS3 supplementation. There were no significant differences in fecal dry weight, pH, or short-chain fatty acid concentrations, nor in the pH, bile acid concentrations, cytotoxicity, or osmolality of fecal water. It is concluded that in healthy men, supplementing the habitual diet for 1 wk with 32 g RS2 or RS3/d compared with glucose had no effect on putative risk factors for colon cancer, except for increasing stool weight and colonic fermentative activity. There were no significant differences between the effects of RS2 and RS3 on the indexes studied.