Glycaemic variability and hypoglycaemia are associated with C-peptide levels in insulin-treated type 2 diabetes.

AIM: The aim of the study was to evaluate the association between C-peptide levels, glycaemic variability and hypoglycaemia in patients with insulin-treated type 2 diabetes (T2D). METHODS: A total of 98 patients with T2D treated with basal-bolus insulin were enrolled in a cross-sectional study. Glycaemic variability and hypoglycaemia were assessed from continuous glucose monitoring (CGM) data recorded over 6 days: Glycemic variability was assessed by calculating the mean coefficient of variation (CV), while hypoglycemia was defined as sensor glucose levels ≤ 3.9 mmol/L or < 3.0 mmol/L. Fasting C-peptide and fasting glucose were measured on day 1. RESULTS: Low levels of fasting C-peptide correlated with higher CV (r = -0.53, P < 0.0001). In a multivariate regression model with HbA1c, body mass index, diabetes duration and total daily insulin dose, only C-peptide was significantly associated with CV. Patients with ≥ 1 episode of hypoglycaemia had significantly lower median C-peptide levels than patients without hypoglycaemia (274 (136-620) pmol/L vs. 675 (445-1013) pmol/L, respectively; P = 0.0004). Also, 17 patients clinically diagnosed with T2D had detectable glutamic acid decarboxylase (GAD) antibodies (≥ 5 U/mL). These GAD-positive patients had significantly lower fasting C-peptide, higher CV and greater frequency of hypoglycaemia than GAD-negative patients. CONCLUSION: In patients with insulin-treated T2D, low levels of C-peptide are associated with greater glycaemic variability and higher risk of hypoglycaemia, suggesting that C-peptide levels should be taken into consideration when optimizing insulin treatment and assessing hypoglycaemia risk.

Influence of orlistat on bone turnover and body composition.

OBJECTIVE: To investigate the influence of the pancreas lipase inhibitor orlistat (OLS) on calcium metabolism, bone turnover, bone mass, bone density and body composition when given for obesity as adjuvant to an energy- and fat-restricted diet. DESIGN: Randomized controlled double-blinded trial of treatment with OLS 120 mg three times daily or placebo for 1 y. SUBJECTS: Thirty obese subjects with a mean body mass index (BMI) of 36.9+/-3.7 kg/m(2) and a mean age of 41+/-11 y. Sixteen patients were assigned to OLS and 14 to placebo. MEASUREMENTS: Dual energy X-ray absorptiometry (DXA) measurements of bone mineral and body composition included total bone mineral content (TBMC), total bone mineral density (TBMD), lumbar spine BMC and BMD, forearm BMC and BMD, fat mass (FM), fat free-mass (FFM), percentage fat mass (FM%) as well as a DXA estimate of the body weight. Body composition (FM, FFM and FM%) was estimated by total body potassium (TBK). Indices of calcium metabolism and bone turnover included serum values of ionized calcium (Ca(++)), iPTH (parathyroid hormone), alkaline phosphatase, 25(OH)-vitamin D, 1,25(OH)(2) vitamin D and osteocalcin as well as fasting urinary ratios of hydroxyproline/creatinine and Ca/creatinine (fU-OHpr/creat, fUCa/creat). RESULTS: There were no significant differences between OLS and placebo groups as to any of the body composition variables (FFM, FM, FM%) at baseline or after 1 y treatment. Weight loss was of 11.2+/-7.5 kg in the OLS group and 8.1+/-7.5 kg in the placebo group (NS). The changes in FM and FM% were significant in both groups determined by DXA as well as by TBK, but the group differences between these changes were not significant. The composition of the weight loss was approximately 80% fat in both groups. FFM only changed significantly by DXA in the OLS group (-1.3 kg), but the difference from the placebo group was not significant. Forearm BMD in both groups, forearm BMC in the OLS group and TBMD in the placebo group fell discretely but significantly, but there were no significant group differences between the OLS and the placebo-treated group. All biochemical variables except s-osteocalcin changed significantly after 1 y in the OLS group, disclosing a pattern of an incipient negative vitamin D balance, a secondary increase in PTH-secretion, and an increase in bone turnover with the emphasis on an increase in resorption parameters (fU-OHpr/creat, fUCa/creat). In the placebo group, only s-25(OH)vitamin D and fU-OHpr/creat changed significantly, but the pattern was also that of a deteriorated vitamin D status and an increase in PTH levels and bone turnover. The only biochemical variable which was significantly different between OLS and placebo groups after one year was the fU-OHpr/creat ratio, which increased from 12.0 to 20.1 in the OLS group but only from 10.9 to 1 3.2 in the placebo group. CONCLUSION: One year's treatment with OLS induces a lipid malabsorption which enhances a dietary weight loss without any significant deleterious effects on body composition. OLS induces a relative increase in bone turnover in favour of resorption, possibly due to malabsorption of vitamin D and/or calcium. However, no changes in bone mass or density are seen after 1 y of OLS treatment apart from those explained by the weight loss itself. Thus 1 y of OLS treatment seems safe from a 'bone preserving' point of view. A vitamin D and calcium supplement should be taken during the treatment.

Fasting gall bladder volume and lithogenicity in relation to glucose tolerance, total and intra-abdominal fat masses in obese non-diabetic subjects.

OBJECTIVE: To investigate whether total body fat mass or fat distribution and associated metabolic disturbances in glucose and lipid metabolism influence the well known gallstone pathogenetic factors in obese subjects in order to explain why some obese subjects develop gallstones and some do not. DESIGN: Cross sectional study of gallstone pathogenetic factors, body composition, fat distribution, glucose and lipid metabolism. SUBJECTS: 57 healthy overweight subjects (aged 26-64y, body mass index (BMI) 30-45 kg/m2). MEASUREMENTS: Total and intra-abdominal fat masses were measured by dual X-ray absorptiometry and abdominal CT scanning, respectively. The lithogenic index was measured in aspirated bile. The gallbladder volume was determined by ultrasound and the gallbladder ejection fraction% by dynamic cholescintigraphy. Plasma cholecystokinin (CCK) concentrations during a meal were measured with a specific radioimmunoassay. Insulin sensitivity was measured by the Minimal Model and glucose tolerance by an oral glucose tolerance test (OGTT). Serum lipid concentrations were measured by standard methods. RESULTS: The gallbladder volume in the fasting state increased with increasing intra-abdominal fat mass (P=0.006) and was increased in subjects with impaired glucose tolerance (41 vs 27 ml, P=0.001). The lithogenic index was > 1 in all subjects and correlated with total fat mass (P=0.04). CONCLUSION: Gallstone pathogenesis in obesity seems to be influenced by the total body fat mass and its regional distribution possibly via mutual association with the glucose tolerance.

Body composition analysis by DEXA by using dynamically changing samarium filtration.

Dual-energy X-ray absorptiometry (DEXA) has a high accuracy for body composition analysis but is influenced by beam hardening and other error sources in the extremes of measurement. To compensate for beam hardening, the Norland XR-36 introduces a dynamically changing samarium filtration system, which depends on the current-absorber thickness. With this system we found a good agreement (r = 0.99) between reference and measured amounts of tissue or fat percentages in a plastic phantom and in smaller (approximately 0.5-4 kg) and larger (approximately 5-20 kg) piles of tissue (ox muscle and lard). Scans of six healthy volunteers covered with combinations of beef and lard (approximately 5-15 kg) showed a good agreement (r = 0.99) between reference and DEXA values of added soft tissue mass and fat percentage. We conclude that the DEXA method (and, in particular, the Norland XR-36 using dynamic filtration) has a high accuracy for body composition analysis. It has a potential for gaining status as a reference method in the future and may presently be used as a supplement to the traditional methods for body composition analysis.

Body composition during weight loss in obese patients estimated by dual energy X-ray absorptiometry and by total body potassium.

OBJECTIVE: To validate the ability of DXA to measure total body composition before and after weight loss and the composition of the lost body mass. DESIGN: Cross sectional and follow-up study of body composition before and after a weight loss of 10.6 +/- 6.8 kg. SUBJECTS: 31 obese subjects with a mean body weight of 105.2 +/- 15.2 kg at baseline, and a mean body weight of 94.6 +/- 16.5 kg at follow-up. MEASUREMENTS: Body composition was measured by dual X-ray absorptiometry, total body potassium counting, and high precision scales before and after a weight loss. RESULTS: DXA and the scales showed a strong linear relation (r = 1). At baseline, however, DXA underestimated the body weight by a maximum of 3.2 kg because the subjects were too large for the scan table. After weight loss body weight measurements were accurate. Before and after weight loss the linear relations between DXA and TBK for FFM were strong (r = 0.92 and 0.93). Bland and Altman plots showed limits of agreement of +/-9 kg before and after weight loss; DXA underestimated FFM in women and overestimated FFM in men. DXA accounted for 80% of the lost body weight. The composition of the lost body mass did not differ from that estimated by TBK (7.6% FFM and 92.4% FM by TBK; 11% FFM and 89% FM by DXA). CONCLUSION: DXA estimates accurately the body composition and the composition of weight loss in groups of obese subjects. However, the scan table may be too small for patients weighing more than 95 kg.

Change in fat-free mass assessed by bioelectrical impedance, total body potassium and dual energy X-ray absorptiometry during prolonged weight loss.

A total of 16 obese women (body mass index (BMI) 30-43 kg m(-2)) participated in a weight reduction study. Before and after a weight loss of 11.7 +/- 7.4 kg (mean +/- SD), body composition was assessed by dual energy X-ray absorptiometry (DXA), and total body potassium counting (TBK). These measurements were compared with bioimpedance analysis (BIA) by applying 11 predictive BIA equations published in the literature. Predictive equations for the present study population were developed, with the use of fat-free mass (FFM) as assessed by TBK and DXA as references in multiple regression analysis. The results of the BIA equations varied widely; FFM was generally overestimated by BIA as compared with DXA and TBK before and after weight loss. During weight loss, the FFM did not change, as estimated by DXA (1.3 +/- 2.3 kg, p > 0.05) and TBK (0.9 +/- 2.9 kg, p > 0.05). The recorded change in impedance (R) was also insignificant. Three BIA equations from the literature, which were not specific for the degree of obesity in the present study group, predicted changes in FFM (from 0.5 + 3.6 to 2.4 +/- 4.4kg, p > 0.05) that were comparable with those estimated by the reference methods. Eight equations from the literature, which included equations specific for the degree of obesity in the study group, and the group specific equations developed for the present population predicted significant changes in FFM during weight loss (from 2.3 +/- 3.0 to 5.0 +/- 3.0 kg, p < 0.05). We conclude that in obesity most predictive equations are unable to predict static body composition and are not reproducible for individuals over time. However, a significant or insignificant change in R (without accompanying predictive equations) may be used to indicate whether FFM is lost or preserved in groups of obese subjects.

Comparison of body composition by dual energy X-ray absorptiometry to other estimates of body composition during weight loss in obese patients with rheumatoid arthritis.

Body composition was determined by dual energy X-ray absorptiometry (DXA) scanning and classical reference methods (40K, 3H2O, and a combination of these in a four-compartment model) in 19 overweight patients with rheumatoid arthritis who underwent a 12-week weight-reducing regimen. The aim of the study was to investigate whether DXA provides a valid estimate of body composition. The results showed that weight as determined by DXA was highly significantly correlated to weight determined by scales. Furthermore, significant correlations were found in the body components (fat-free mass, fat mass) determined by DXA, 40K, 3H2O and the four-compartment model. Mean values differed slightly but significantly. With respect to changes in body composition, no significant correlations were found between any of the methods, except for the weight loss recorded by DXA and scales, and loss of fat mass (and fat free mass) estimated by 3H2O and the four-compartment model. The sparseness of correlations reflected the small changes in fat-free mass and fat mass (2.6 and 1.7 kg respectively), and the fact that changes were comparable to measurement errors of the various methods. We suggest that DXA scanning is a valid supplement for determination of body composition. Validation of DXA scanning requires new experimental in vitro investigations, which, incidentally, also applies to the classical reference methods.

Body composition in normal subjects: relation to lipid and glucose variables.

OBJECTIVE: To describe sex- and age-dependent values of total and regional body composition as determined by dual-energy X-ray absorptiometry (DXA) in normal subjects, and furthermore to relate body composition measurements to blood lipids, glucose and insulin concentrations. DESIGN: A cross-sectional study. SUBJECTS: 173 (84 male and 89 female) healthy subjects, BMI < 30 kg/m2. MEASUREMENTS: Body composition parameters including data on total bone mineral content (TBMC), total bone mineral density (TBMD), lean body soft tissue mass (LTM), total and regional fat mass (FM) were estimated in all subjects. In 87 of the subjects fasting blood glucose, S-insulin and lipid profile were measured. RESULTS: The study population was for each sex divided into five decades for which results on body composition and blood lipids are presented. Body weight increased 2 kg per age decade, representing a significant increase in both total FM and relative FM (FM%BW) with age, and in males a central accumulation of FM. LTM decreased significantly in males but not in females, whereas TBMC and TBMD remained constant in males, but decreased in females. A significant correlation between relative FM and S-cholesterol, S-triglyceride, and in males S-insulin was found. CONCLUSION: The present study gives coherent data on bone mineral content, lean body soft tissue mass total and regional fat mass for 173 healthy subjects with a BMI below 30 kg/m2. Total body fat mass increases, and lean mass decreases with age. In males a simultaneous central accumulation of fat mass is observed. The well-known relationship between central obesity and lipids is confirmed even in non-obese subjects.

Validity of dual X-ray absorptiometry scanning for determination of body composition in IDDM patients.

Data on body composition in patients with insulin-dependent diabetes mellitus (IDDM) are scarce. Dual X-ray absorptiometry (DXA) scanning has proved useful for this purpose in other groups of patients. We tested the validity of the DXA scanner for the determination of fat-free mass (FFM) and fat mass in IDDM patients and control subjects, as compared to other reference methods, i.e. total body potassium by 40K whole body counting (TBK), total body water by tritiated water (TBW), bioelectrical impedance analysis (BIA) and 24-h urinary creatinine excretion (Ucrea). A total of 13 healthy controls, 5 males and 8 females, aged 34.2 years +/- SD 10.4, and 11 IDDM patients, 5 males, 6 females, aged 28.1 years +/- 7.3, diabetes duration 4.2 +/- 2.9 (1.0-9.9), were examined. The patients had no long-term diabetic complications and they had normal ophthalmoscopy and urine albumin excretion. The agreement between FFM estimated by DXA and the other methods, expressed as mean difference +/- 2 SD was; for DXA vs. TBK, 0.09 +/- 6.26 and 0.50 +/- 5.26 kg for controls and IDDM patients respectively; DXA vs. TBW, -2.07 +/- 2.56 and -1.07 +/- 4.58 kg; DXA vs. Ucrea, -2.62 +/- 8.02 and 2.00 +/- 10.0 kg; DXA vs. BIA, -7.90 +/- 8.92 and -7.85 +/- 2.32 kg. The results obtained with BIA were significantly different from the other methods for both control subjects and IDDM patients. In conclusion, DXA scanning is a precise and valid method for estimation of fat-free mass in IDDM patients.

Massive weight loss restores 24-hour growth hormone release profiles and serum insulin-like growth factor-I levels in obese subjects.

In the present study, we 1) determined whether the impaired spontaneous 24-h GH secretion as well as the blunted GH response to provocative testing in obese subjects are persistent disorders or transient defects reversed with weight loss and 2) investigated 24-h urinary GH excretion and basal levels of insulin-like growth factor-I (IGF-I), IGF-binding protein-3 (IGFBP-3), as well as insulin in obese subjects before and after a massive weight loss. We studied 18 obese subjects (age, 26 +/- 1 yr; body mass index, 40.9 +/- 1.1 kg/m2); 18 normal age-, and sex-matched control subjects; and 9 reduced weight obese subjects after a diet-induced average weight loss of 30.3 +/- 4.6 kg. Twenty-four-hour spontaneous GH secretion was estimated by obtaining 3240 integrated 20-min blood samples using a constant blood withdrawal technique and computerized algorithms. Body composition was determined using anthropometric measurements and dual energy x-ray absorptiometry scanning (DXA). In the obese subjects, 24-h spontaneous GH release profiles and the GH responses to insulin-induced hypoglycemia and L-arginine as well as basal IGF-I levels and the IGF-I/IGFBP-3 molar ratio were decreased, whereas insulin levels were elevated compared to those in normal subjects. In obese subjects, 24-h spontaneous GH secretion and serum IGF-I levels were inversely related to abdominal fat (r = -0.67; P < 0.01) and percent body fat (r = -0.69; P < 0.01), respectively. The decreased 24-h spontaneous GH release profiles, the decreased GH responses to insulin-induced hypoglycemia and L-arginine, the decreased basal IGF-I levels and IGF-I/IGFBP-3 molar ratio, as well as the elevated insulin levels were returned to normal after a massive weight loss in the obese subjects. In conclusion, the present study has shown reversible defects in 24-h spontaneous GH release profiles, basal IGF-I levels, and the IGF-I/IGFBP-3 molar ratio in obese subjects. The recovery of the 24-h GH release points to an acquired transient defect rather than a persistent preexisting disorder.

Body composition in hemodialysis patients measured by dual-energy X-ray absorptiometry.

Dual-energy X-ray absorptiometry (DXA) measures three of the principal components of the body: fat mass, lean soft-tissue mass (comprising muscle, inner organs, and the body water), and the bone mineral content. The purpose of this study was to test the estimation capacity of DXA when it is applied to patients with end-stage renal failure. Twenty dialysis patients were examined by DXA before and after one hemodialysis session. A highly significant positive correlation between weight measurements performed by conventional scales and DXA was found. A positive correlation between fluid loss during dialysis and reduction in fat-free mass (lean soft-tissue mass plus bone mineral content) was observed by DXA. The estimation of the fat-free mass was independent of the amount of fluid loss. No significant differences in variance between the data obtained before and after the dialysis were observed. We conclude that DXA is a useful tool for estimating the magnitude of body compartments in patients with end-stage renal failure.

[Non-invasive measurement of body composition]. / Ikkeinvasiv måling af kropssammensaetning.

The concept of body composition covers the division of the body into a number of compartments. The most important are the fat mass (FM), the fat-free mass (FFM), the total body protein and the total body bone mineral content. Numerous methods for the measurement of body composition are available. The three classical methods for the measurement of FM and FFM, namely underwater weighing, measurement of total body potassium and measurement of total body water by isotope dilution, are often regarded as reference methods. However, newer methods such as computed tomography, neutron activation analysis and dual energy X-ray absorptiometry are increasingly used because of their reliability and ability for independent measurement of two or more components. Bioelectrical impedance analysis has become popular because of its clinical applicability. Three- or four-compartment models involving combination of two, three or more separate methods are more accurate than single methods, but are usually confined to research purposes because of the laborious measurement procedures. Computed tomography and dual energy X-ray absorptiometry have the unique possibility of regional measurements of body composition. Fat distribution and relative overweight may be estimated by simple anthropometric measures such as skinfold thicknesses. There are many applications for body composition measurements in research and clinical practice. These include treatment of obesity, growth hormone deficiency, diabetes mellitus and climacteric changes, as well as clinical nutrition and estimation of the hydration of dialysis patients and of critically ill intensive or surgical patients.

[No increase in the prevalence of vertebral fractures among postmenopausal women over a 10-year period]. / Ingen stigning over ti år i praevalensen af columnafraktur blandt postmenopausale kvinder.

We examined whether the prevalence of vertebral fracture in otherwise healthy, 70-year-old Danish women had increased over a period of ten years. The population-based, epidemiological study included two age-matched, representative samples of postmenopausal women. Group 1 (1979) consisted of 173 healthy women without secondary causes of osteoporosis, Group 2 (1989) of 387 women. X-rays of the thoraco-lumbar spine were assessed for vertebral fracture by five radiological methods. There was no significant difference between the two groups in the prevalence of vertebral fracture and the 95% confidence intervals overlapped completely in all methods. The prevalence rates varied by method from 35% to 80% but the distribution of fracture types was similar in the two groups. We conclude that the prevalence of vertebral fractures due to postmenopausal osteoporosis has not increased since 1979 in suburban Copenhagen, and that comparison of prevalences requires the same method of radiological assessment.

No secular increase in the prevalence of vertebral fractures due to postmenopausal osteoporosis.

We examined whether the prevalence of vertebral fractures in otherwise healthy, 70-year-old Danish women had increased during an interval of 10 years. The population-based epidemiological study included two age-matched groups of postmenopausal women. Group 1 consisted of 70-year-old women (n = 386) living in a defined area of suburban Copenhagen recruited in 1979 for an epidemiological study. Of the 285 women who were entered, 173 were judged healthy, without secondary causes of osteoporosis. Group 2 was recruited by sending questionnaires to all women aged 68-72 years living in the same area in 1989. Of the 512 women who attended a medical screening, 387 were found to be without secondary causes of osteoporosis and had a spinal radiograph. Radiographs of the thoracolumbar spine were assessed for vertebral fracture by five radiological methods. There was no significant difference between the two groups in the prevalence of vertebral fractures and the 95% confidence intervals overlapped completely in all methods. The prevalence rates varied by method from about 35% to more than 80% but the distribution of fracture types was similar in the two groups. We conclude that the prevalence of vertebral fractures due to postmenopausal osteoporosis has not increased since 1979 in otherwise healthy women residing in suburban Copenhagen, and that comparison of prevalences between studies requires that they use the same method of radiological assessment.

Postmenopausal hormone replacement therapy prevents central distribution of body fat after menopause.

The reduction in cardiovascular risk induced by hormone replacement therapy is only partly explained by changes in serum lipids and lipoproteins. As body composition and body fat distribution in particular are independent predictors of cardiovascular disease, we investigated the effect of postmenopausal hormone therapy on body composition parameters directly measured. Sixty-two early postmenopausal women were followed up for 2 years in a prospective, randomized, placebo-controlled study. We found that combined estrogen-progestogen therapy prevented the increase in abdominal fat after menopause (P less than .05), and that this effect was independent of the effect on serum lipids and lipoproteins. The therapy reduced postmenopausal bone loss significantly (P less than .001), whereas it did not have a statistically significant influence on total body fat mass or total lean body mass. The findings of the present study suggest that some of the protective impact of postmenopausal hormone therapy on cardiovascular disease may be explained by the effect on body composition, in particular abdominal fat.

The impact of measurement errors on the diagnostic value of bone mass measurements: theoretical considerations.

It has become clear over the last decade that correlations between measurements of forearm bone mineral content (BMCarm) by single-photon absorptiometry (SPA) and measurements of spinal bone mineral density (BMDspine) by dual-photon absorptiometry (DPA) in healthy subjects and patients with spinal fractures are invariably significant, but not very powerful (i.e. r = 0.5-0.7). Nonetheless, several recent studies have shown that appendicular bone mass measurements discriminate between spinal fracture and non-fracture at least as well as do spinal DPA measurements. Correlations of a given parameter with measured BMDspine are less important than those with true BMDspine. To establish the latter we made the following assumptions: (1) accuracy errors or SPA BMCarm and DPA BMDspine measurements of 2%-4% and 8%-10%, respectively; and (2) a measured biological variation of SD = 14% for both BMCarm and BMDspine, corresponding to that of healthy women at the menopause. On these assumptions, we found that a correlation between true BMCarm and true BMDspine at about r = 0.8-0.9 yields a correlation between measured BMCarm and measured BMDspine at about r = 0.6--corresponding to experimental data in healthy women at the menopause. Furthermore, we found that the correlation between DPA measured BMDspine and true BMDspine is about the same as that between the SPA measured BMCarm and the true BMDspine. Thus, with the assumptions given above, spinal (DPA) and fore-arm (SPA) measurements appears to predict equally the true BMDspine in healthy perimenopausal women.

Precision in assessment of osteoporosis from spine radiographs.

Inter- and intra-observer variation in spine radiographs of 100 osteoporotic women and longitudinal change in roentgenologic status after 1 year of antiosteoporotic treatment were assessed. The method applied was naked eye inspection, and a score system estimating severity of fractures - vertebral deformation score (VDS). Agreement was assessed by the Kappa coefficient corrected for agreement by change. The results showed a satisfactory inter- and intraobserver agreement for wedge (Kappa = 0.72 and 0.90) and compression fractures (Kappa = 0.60 and 0.92). The method proved less reliable for endplate fractures (Kappa = 0.39 and 0.73). We think that the method of investigation is well suited for monitoring treatment effects in longitudinal studies.

Validation of body composition by dual energy X-ray absorptiometry (DEXA).

The present study validates the use of dual energy X-ray absorptiometry (DEXA) for measurement of body composition. The precision error was expressed as the SD (CV%) for fat mass, FAT%, lean tissue mass, and total body bone mineral: 1.1 kg (6.4%), 1.6% (5.7%), 1.4 kg (3.1%), and 0.03 kg (1.2%), respectively. The accuracy study in vitro used (1) mixtures of water and alcohol, (2) mixtures of ox muscle and lard, and (3) dried bones. In the clinically relevant range of values there were only small influences on DEXA measurements of variations in amount and composition of the soft tissue equivalents. The accuracy study in vivo compared the components of body composition measured recently by DEXA and earlier by dual photon absorptiometry, counting of naturally occurring total body 40K, and body density by underwater weighing in 25 healthy adult subjects. We found agreement between fat percentage (and lean body mass) by DEXA and the three established measurements modalities; mean differences were (-5.3 to -0.4%) and (-0.7 to 2.5 kg) for fat percentage and lean body mass, respectively. We conclude that DEXA provides a new method of measuring body composition with precision and accuracy errors, which are compatible with the application of DEXA in group research studies and probably also in clinical measurements of the single subject.

Measurement of body fat in elderly subjects by dual-energy x-ray absorptiometry, bioelectrical impedance, and anthropometry.

Body fat was measured in 46 elderly subjects by dual-energy x-ray absorptiometry [BF(DEXA)], bioelectrical impedance analysis (BIA), and anthropometry. Equations for prediction of the body fat (by DEXA) of elderly people by BIA and/or anthropometry were developed. The prediction of body fat (by DEXA) by anthropometric variables alone gave an r2 of 0.94 and the corresponding SEEs were 1.61 kg for men and 2.43 kg for women. When BIA variables were added as predictors, r2 increased by 2-5% (P less than 0.05) and the corresponding SEE decreased by 25% (P less than 0.05). The prediction of body fat (by DEXA) in elderly subjects and by BIA or anthropometry with equations developed in populations of young healthy adults (adapted from the literature) was generally not good although the correlation coefficients were high (r greater than 0.9, P less than 0.001), which suggests that our equations may improve prediction of body fat in elderly subjects.