Effect of dark chocolate on plasma epicatechin levels, DNA resistance to oxidative stress and total antioxidant activity in healthy subjects.

Dark chocolate (DC) may be cardioprotective by antioxidant properties of flavonoids. We investigated the effect of DC (860 mg polyphenols, of which 58 mg epicatechin) compared with white chocolate (WC; 5 mg polyphenols, undetectable epicatechin) on plasma epicatechin levels, mononuclear blood cells (MNBC) DNA damage and plasma total antioxidant activity (TAA). Twenty healthy subjects followed a balanced diet (55 % of energy from carbohydrates, 30 % from fat and 1 g protein/kg body weight) for 4 weeks. Since the 14th day until the 27th day, they introduced daily 45 g of either WC (n 10) or DC (n 10). Whole experimental period was standardised in antioxidant intake. Blood samples were collected at T(0), after 2 weeks (T(14)), 2 h and 22 h after the first chocolate intake (T(14+2 h) and T(14+22 h)), and at 27th day, before chocolate intake (T(27)), 2 h and 22 h after (T(27+2 h) and T(27+22 h)). Samples, except for T(14+2 h) and T(27+2 h), were fasting collected. Detectable epicatechin levels were observed exclusively 2 h after DC intake (T(14+2 h) = 0.362 (se 0.052) micromol/l and T(27+2 h) = 0.369 (se 0.041) micromol/l); at the same times corresponded lower MNBC DNA damages (T(14+2 h) = - 19.4 (se 3.4) % v. T(14), P < 0.05; T(27+2 h) = - 24 (se 7.4) % v. T(27), P < 0.05; T(14+2 h) v. T(27+2 h), P = 0.7). Both effects were no longer evident after 22 h. No effect was observed on TAA. WC did not affect any variable. DC may transiently improve DNA resistance to oxidative stress, probably for flavonoid kinetics.

Nutritional counselling in disabled people: effects on dietary patterns, body composition and cardiovascular risk factors.

AIM: Disabled persons are frequently affected by nutritional status impairment, consequent to quantitative and qualitative inadequacy of diet and physical inactivity, resulting in a significant reduction of fat-free mass and bone mineral density (BMD), and an over-expression of fat mass and an increased number of biochemical risk factors for chronic degenerative diseases. The aim of this study was to analyse the applicability and the efficacy of a nutritional counselling intervention in order to improve dietary intake and nutritional status in disabled people. METHODS: Thirty-seven disabled subjects (24 with physical disability and 13 with both mental retardation and physical disability; age 33.5+/-9.2 years) underwent an assessment of nutritional status, and an intervention with nutritional counselling was proposed to each patient for one year. Anthropometric measurements, indirect calorimetry, dual-energy X-ray absorptiometry, dietary intake, and biochemical analysis at baseline (T0) and after one year (T1) of counselling intervention were performed. RESULTS: Sixty-five percent of patients dropped out. Overall, no significant improvement in cardiovascular risk factors, body composition and dietary patterns was reported at T1 in completer subjects. Six subjects who were obese or overweight at T0, reported significant weight and fat mass (FM) reduction at T1 (P=0.01 and P=0.00, respectively). CONCLUSION: Nutritional counselling seems to be ineffective and poorly applicable to disabled people. Further studies should be directed towards a treatment program associated with careful screening, motivation analysis, and follow-up in this patient population.

Poor agreement between a portable armband and indirect calorimetry in the assessment of resting energy expenditure.

BACKGROUND & AIMS: To evaluate the agreement between resting energy expenditure (REE) estimated by a portable armband and measured by indirect calorimetry. METHODS: One-hundred and twenty-seven women and 42 men with a mean (SD) age of 44 (12) years and a body mass index of 30.2 (5.4) kg/m(2) were studied. REE was estimated using the Sense Wear Pro 2 Armband (SWA), measured using the Sensor Medics 29 metabolic cart (V(max)), and estimated using Schofield's equation. The limits of agreement (LOA) and the concordance correlation coefficient (CCC) were used to evaluate the interchangeability of the methods. RESULTS: The LOA between REE(SWA) and REE(Vmax) were wide in both women (-269 to 378 kcal/day) and men (-330 to 545 kcal/day) and CCC was low (0.579 in females and 0.583 in males, p<0.0001 for both). REE(Schofield) agreed with REE(Vmax) to a similar degree (CCC=0.563 in females and 0.500 in males, p<0.0001 for both). CONCLUSIONS: SWA and indirect calorimetry are not interchangeable methods for the assessment of REE in normal-weight and obese subjects.

Evaluation of air-displacement plethysmography and bioelectrical impedance analysis vs dual-energy X-ray absorptiometry for the assessment of fat-free mass in elderly subjects.

OBJECTIVE: To evaluate air-displacement plethysmography (ADP) and bioelectrical impedance analysis (BIA) vs dual-energy X-ray absorptiometry (DXA) for the assessment of fat-free mass (FFM) in healthy elderly subjects. SUBJECTS: Forty-two women and twenty-six men aged 60-84 years. METHODS: FFM was measured by DXA and ADP. Body impedance (Z) was measured by four-polar BIA and the impedance index (ZI) was calculated as stature(2)/Z. Selection of predictors (gender, age, weight and ZI at 5, 50 and 100 kHz) for BIA algorithms was carried out using bootstrapped stepwise linear regression on 1000 samples of 68 subjects. Limits of agreement were used as measures of interchangeability of ADP and BIA with DXA. RESULTS: The limits of agreement of ADP vs DXA were -11.0 to 2.4 kg in males and -4.8 to 2.2 kg in females. Gender, weight and ZI(100) were selected as predictors of FFM by bootstrapped stepwise linear regression. In males, ZI(100) (-12.2 to 12.2 kg) was much less accurate than weight (-6.0 to 6.0 kg) at predicting FFM and their combination did not improve the estimate (-6.0 to 6.0 kg). In females, ZI(100) (-6.8 to 6.8 kg) was less accurate than weight (-5.6 to 5.6 kg) at predicting FFM and their combination improved the estimate only slightly (-5.0 to 5.0 kg). CONCLUSIONS: In healthy elderly subjects, (1) ADP and DXA are not interchangeable for the assessment of FFM, especially in males; and (2) ZI(100) is not superior to weight for the prediction of FFM and their combination is of little advantage and only in females.

Circulating salicylic acid is related to fruit and vegetable consumption in healthy subjects.

Salicylic acid (SA) is a natural phenolic compound known as the active principle of aspirin. Its presence in vegetal sources suggests that fruit and vegetable (FV) consumption could produce measurable SA serum concentrations in human subjects not taking aspirin. The aim of this study was to investigate the relationship between FV intake and circulating SA in healthy subjects. Thirty-eight volunteers (twenty-two males and sixteen females) were recruited from an Italian university campus. They recorded their food intake for 7 d to evaluate dietary consumption and, in particular, FV intake; fasting blood samples were taken on the morning of the eighth day to measure SA serum concentration, using a sensitive stable isotope dilution and GC-MS method. Median SA serum concentration was 0.124 mumol/l (range 0.028-0.295). Circulating SA was significantly related to FV consumption, both to the mean daily intake (r2 0.13, P = 0.03) and to the last day intake (r2 0.16, P = 0.01). The subjects in the highest FV intake quartile in the preceding day (>4.75 servings) had significantly higher SA concentrations than in the lowest quartile ( < 2.3 servings) (median concentrations 0.188 and 0.112 mumol/l, respectively; P = 0.04). This study proved that, after overnight fast, human subjects not taking aspirin display circulating SA in amounts related to the FV consumption. It is therefore possible that the beneficial effects of regular FV consumption in man could also depend on low chronic SA exposure.

Is ghrelin a signal of decreased fat-free mass in elderly subjects?

OBJECTIVE: Aging is associated with appetite decline, weight loss, reduced fat-free mass (FFM), and increased fat mass (FM). Ghrelin and leptin are short- and long-term determinants of energy balance respectively, whose dysregulation could alter food intake. We evaluate the relationship of circulating ghrelin and leptin responses to standardized oral mixed nutrient load (SOMNL) with body composition, daily food intake, and insulin sensitivity in healthy elderly subjects (ES). DESIGN AND METHODS: Twenty-six ES (12/14 M/F, 69+/-4 years) and ten young healthy controls (LY) (5/5 M/F, 27+/-3 years) were studied at the International Center for the Assessment of Nutritional Status (Milan, Italy) with air plethysmography, dual energy X-ray absorptiometry, indirect calorimetry, and dietary intake assessment. Basal and postprandial ghrelin, leptin, testosterone, glucose, insulin and C-peptide concentrations, and insulin resistance (homeostasis model assessment (HOMA-R)) and sensitivity (quantitative insulin-sensitivity check index (QUICKI)) were evaluated. RESULTS: Basal ghrelin levels were similar in ES and LY, whereas leptin was higher in ES than LY, in agreement with the higher amount of FM. Basal and percentage change in ghrelin were inversely related to FFM, appendicular skeletal muscle mass (SMM), and QUICKI, but not to FM. Basal and percentage change in leptin were directly related to FM and not to FFM indexes. Ghrelin basal concentration was negatively correlated with energy and protein intake and with QUICKI. Percentage change in Ghrelin after SOMNL correlated negatively with protein intake, but positively with resting energy expenditure and energy intake, and glucose, insulin, C-peptide basal concentrations, and HOMA-R. CONCLUSION: In ES, basal and postprandial ghrelin increases with FFM, specifically SMM, reduction, whereas leptin increases with relative FM increases.

Measurement of salicylic acid in human serum using stable isotope dilution and gas chromatography-mass spectrometry.

A simple, highly selective, and sensitive method using stable isotope dilution and gas chromatography-mass spectrometry has been developed to quantify salicylic acid (SA) at concentrations naturally occurring in biological fluids, such as in the serum of subjects not taking aspirin. After extraction of liquid-liquid with diethyl ether and ethyl acetate and preparation of the tert-butyldimethylsilyl derivative, SA content was detected using deuterated SA as internal standard. The mean recovery of SA from serum was 85 +/- 6%. Intra- and interday precision and % relative error were <15% in all cases. With a detection limit of 0.6 ng and a quantification limit of 2 ng, the method is therefore also adequate for population studies because of the small amount of blood necessary to perform the analyses.

Evaluation of nutritional status in children with refractory epilepsy.

BACKGROUND: children affected by refractory epilepsy could be at risk of malnutrition because of feeding difficulties (anorexia, chewing, swallowing difficulties or vomiting) and chronic use of anticonvulsants, which may affect food intake and energy metabolism. Moreover, their energy requirement may be changed as their disabilities would impede normal daily activities. The aim of the present study was to evaluate nutritional status, energy metabolism and food intake in children with refractory epilepsy. METHODS: 17 children with refractory epilepsy (13 boys and 4 girls; mean age 9 +/- 3,2 years; Body Mass Index 15,7 +/- 3,6) underwent an anthropometric assessment, body composition evaluation by dual-energy X-ray absorptiometry, detailed dietetic survey and measurement of resting energy expenditure by indirect calorimetry. Weight-for-age, height-for-age (stunting) and weight-for-height (wasting) were estimated compared to those of a reference population of the same age. RESULTS: 40% of children were malnourished and 24% were wasted. The nutritional status was worse in the more disabled children. Dietary intake resulted unbalanced (18%, 39%, 43% of total daily energy intake derived respectively from protein, lipid and carbohydrate). Adequacy index [nutrient daily intake/recommended allowance (RDA) x 100] was < 60% for calcium iron and zinc. CONCLUSION: many children with refractory epilepsy would benefit from individual nutritional assessment and management as part of their overall care.

Nutritional status and dietary patterns in disabled people.

BACKGROUND AND AIM: Obesity, cardiovascular diseases, diabetes and osteoporosis are the most frequent pathologies among people with a severe reduction of physical activity. The impairment in nutritional status, consequent to quantitative and qualitative inadequacy of diet, could be one of the first steps in the development of co-morbidities in disabled subjects. In order to evaluate this hypothesis we investigated the nutritional status and the food intake in patients with physical or mental disabilities. METHODS AND RESULTS: Thirty-seven disabled subjects (24 with exclusively physical inactivity and 13 with mental retardation and physical inactivity) mean age 33.5+/-9.2 years and 25 healthy subjects (mean age 31.0+/-9.3 years) were enrolled. Anthropometric measurements, indirect calorimetry, dual-energy X-ray absorptiometry, dietary intake and biochemical parameters were collected for each subject. Forty percent of disabled were overweight and 14% were obese. Fat free mass (FFM) and bone mineral content (BMC) was lower and fat mass (FM) was higher than able-bodied control. Absolute resting energy expenditure (REE) was lower in disabled subjects, but this difference disappeared when REE was normalized to FFM. Dietary intake resulted unbalanced (16%, 31%, 50% of total daily energy intake derived from protein, lipid and carbohydrate respectively) with a distribution of dietary fatty acid quite far from the recommended ratio [3.1(SFA):4.1(MUFA):1.0(PUFA)] and an excessive consumption of simple carbohydrates (mean intake 17.5+/-4.9%). Insufficient intake of fibre, iron, calcium, potassium and zinc was also found. Finally, alterations in the cholesterol profile were evident in more than one third of the disabled subjects, whereas fasting glucose intolerance was evident in one fourth. CONCLUSION: This study shows a consistent nutritional status impairment in disabled patients resulting in an reduction of FFM and BMC, in an over-representation of FM and in a number of biochemical risk factors for cardiovascular disease. The altered nutritional status is counterparted by a widespread inadequacy of dietary patterns. This nutritional and dietary impairment occurs both in subjects with mental and physical diseases.

Comparison between daidzein and genistein antioxidant activity in primary and cancer lymphocytes.

The main objective of this study was to compare the protective effect of daidzein and genistein against induced oxidative damage in Jurkat T-cell line and in peripheral blood lymphocytes of healthy subjects. After supplementation of cells with isoflavones (from 2.5 to 20micromol/L in Jurkat T-cell and from 0.01 to 2.5micromol/L in primary lymphocytes, 24h), we determined DNA damage induced by hydrogen peroxide using the comet assay and lipid peroxidation evaluating malondialdehyde (MDA) production after ferrous ion treatment. Supplementation of Jurkat cells and primary lymphocytes with both isoflavones significantly increased DNA protection from oxidative damage at concentrations between 0.1 and 5micromol/L (P<0.05), and with just daidzein, at concentrations higher than 2.5micromol/L, there was a decrease in the production of MDA (P<0.05). Our results seem to support that daidzein is just as effective as genistein in protecting cells against oxidative damage especially with respect to DNA. Moreover, since the protective effect was found at concentrations reachable in plasma after soy consumption (less than 2micromol/L), it can be assumed that the antioxidant activity of isoflavones could really contribute to the healthy properties of soy.

Time course of total and distrectual weight gain after refeeding in anorexia nervosa.

Anorectic patients who achieve complete recovery from the eating disorder can obtain a favorable psychosocial outcome but the long-term nutritional outcome is ill-defined. We investigated the time course of total and distrectual body composition during and after refeeding in 32 female patients with anorexia nervosa. Patients were enrolled at their lowest weight (T0) and re-examinated after a 15% weight gain (at a mean of 3 months, T1; n=17) and after 3 years of stable weight recovery (T2; n=8). At T2 patients were compared to a control group of 8 healthy females matched for age and body mass index. All subjects underwent dual X-ray absorptiometry and anthropometry at each visit. At T0, the 32 subjects were at 61%+/-8% of ideal body weight (IBW) with severe reductions in fat mass (FM; 7.1%+/-4.5%), fat free mass (FFM) and bone mineral content (BMC). At T2, the 8 subjects had gained 40% of initial weight, but remained at 85.1%+/-7.7% of IBW ( p<0.01 vs. controls), with a percent FM comparable to that of controls and an absolute FFM still deficient. BMC did not improve at T2 and remained 79% of that in controls. FM depletion was more severe in the limbs than in the trunk and at T2 the trunk/limb FM ratio remained greater than that in controls. These data strongly suggest that continued nutritional surveillance and support is necessary throughout these patients' lives, even after correction of the psychiatric illness and of severe underweight.

Lycopene and vitamin C concentrations increase in plasma and lymphocytes after tomato intake. Effects on cellular antioxidant protection.

OBJECTIVE: This study seeks to verify whether the regular consumption of small amounts of tomato products can protect lymphocyte DNA and lipids from oxidative damage. DESIGN: Standardized dietary intervention. SUBJECTS: Twelve healthy female subjects (mean age 25.2 y). INTERVENTION: Subjects were instructed to follow a standardized diet for 1 week, followed by 3 weeks consumption of the same diet enriched with small amounts of different tomato products providing as a mean 8 mg lycopene, 0.5 mg beta-carotene and 11 mg vitamin C per day. Plasma and lymphocyte concentrations of carotenoids, vitamin C and vitamin E were analysed. Ex vivo protection of lymphocyte DNA from oxidative injury produced by iron ions was evaluated by means of the Comet assay, and lipid peroxidation by HPLC analysis of malondialdehyde (MDA). RESULTS: Dietary intervention with tomato products increased lycopene concentration both in plasma (P < 0.001) and lymphocytes (P < 0.01). Vitamin C concentrations increased by approximately 35% in plasma (P < 0.05) and by approximately 230% in lymphocytes (P < 0.005). Vitamin E decreased significantly in plasma (P < 0.0001) but not in lymphocytes. Finally, there was an improved protection from DNA oxidative damage (P < 0.05) with no significant effect on MDA levels. CONCLUSIONS: Our results suggest that tomato products are not only good sources of lycopene but also sources of bioavailable vitamin C. A Regular intake of small amounts of tomato products can increase cell protection from DNA damage induced by oxidant species. This effect may originate from the synergism of different antioxidants present in tomatoes.

Determination of oxidative status in breast and formula milk.

AIM: To investigate to what extent formula milk and stored breast milk, commonly used in hospitals, could be pro-oxidant sources for newborn babies. METHODS: We determined total antioxidant capacity and lipid peroxidation products, such as lipid peroxides, TBARS and conjugated dienes, in fresh and stored (at -20 degrees C) samples of breast milk and in different brands of formula milk. RESULTS: There were notable differences in the oxidation parameters in several brands of formula milk, particularly concerning the levels of lipid peroxides and total antioxidant capacity. No difference was found in the mean total antioxidant capacity between formula and breast milk, even if the vitamin content is much higher in formula milk than in breast milk. On the contrary, all the considered lipid peroxidation products were higher in human milk (HM) than formula milk (FM), and lipid peroxides were much higher in HM stored at -20 degrees C. Many differences were found between different formula milks. CONCLUSION: There was a conspicuous formation of lipid peroxides in HM stored at -20 degrees C, which was probably caused by an increased presence of free fatty acids due to lipoprotein lipase activity during storage. Unexpectedly, even fresh HM had a higher concentration of lipid peroxidation products when compared to FM. This could be ascribed to the higher susceptibility of HM to degradation during analysis because of manipulation and light exposure. However, it is also interesting that the high content of lipid peroxides did not correspond to a low total antioxidant capacity in either breast or formula milk. This could signify that such levels of lipid peroxidation products might be present naturally in milk and HM after expression is subject to a strong peroxidation either at room temperature or at -20 degrees C.

Feasibility of air plethysmography (BOD POD) in morbid obesity: a pilot study.

The assessment of body composition (BC) in morbidly obese patients is a difficult procedure. Air-displacement plethysmography (ADP), which measures body density, is a very promising technique for BC assessment in health and disease. However, there are very few data about the feasibility of applying ADP on morbidly obese patients, which theoretically could be affected by large body size and difficulty in lung volume measurements. The main aim of this pilot study was to evaluate the feasibility of using ADP for BC assessment in morbidly obese patients. We studied nine subjects (6 males and 3 females) who had a mean age (+/-SD) of 47.0+/-13.5 years and body mass index (BMI) of 46.6+/-7.7 kg/m(2) (range 36.4-58.8). All patients could fit into the instrument chamber and perform the manoeuvre for pulmonary plethysmography. Mean lung volume was 3.9+/-1.2 l and mean percent body fat was 53.1+/-6.6 (range 46.0-67.5). These results indicate that ADP appears to be suitable for patients with BMI over 40 kg/m(2) and produces realistic BC data.

Body composition assessment: an indispensable tool for disease management.

Recent conceptual and technology advancements fostered a rapid development in the field of body composition assessment and provided new and powerful investigative tools. Densitometry, isotopic dilution, bioelectrical impedance, whole-body counting, neutron activation, X-ray absorptiometry, computed tomography, magnetic resonance imaging, and spectroscopy have been the most widely employed methods. The result of this effort is the discovery that body composition at both molecular and cellular or tissue levels is affected by virtually all the pathologic conditions found in medical textbooks. The field is now mature for the clinical translation of this research. Some applications rely on a very solid base and their clinical use has been fully codified. Others still need reference values diversified on a regional and ethnic scale, consensus for interpretation of values, and guidelines for clinical indications. Only after these requirements are satisfied will it be possible to adopt specific practical guidelines, the most reasonable basis for acceptance and accreditation by care providers. Some applications are already being used in several settings. Therefore, establishing the guidelines for clinical application of body composition assessment methods is not only important for physicians and their patients, but is also urgent so as to prevent misuse and to ensure correct communication with the media in this field.

Body composition assessment in spinal cord injury subjects.

Total and segmental body composition (fat mass, FM; fat-free mass, FFM; bone mineral density, BMD) were evaluated in 13 sedentary spinal cord injury (SCI) subjects and in 13 able-bodied healthy males (control, C) using dual X-ray absorptiometry (DXA) and skinfold methods. In the SCI group, total FM was significantly higher (31.1+/-8.2 vs. 20.8+/-6.9%) and total FFM was significantly lower (62.2+/-8.9 vs. 73.5+/-6.4%) than in C subjects. Total BMD did not differ between the SCI and C groups (1.20+/-0.11 vs. 1.30+/-0.11 g/cm(2)). In the SCI group, segmental FM was higher in the legs and trunk, whereas BMD was lower in legs only. The skinfold method significantly underestimated FM in the SCI group. Body composition is severely modified in paralyzed segments. The predictive equations developed for healthy populations appear to be inapplicable to SCI subjects.

Black tea extract supplementation decreases oxidative damage in Jurkat T cells.

The purpose of this study was to investigate the protective effect of black tea (BT) extract against induced oxidative damage in Jurkat T-cell line. Cells supplemented with 10 or 25 mg/L BT were subjected to oxidation with ferrous ions. Malondialdehyde (MDA) production as marker of lipid peroxidation, DNA single strand breaks as marker of DNA damage, and modification of the antioxidant enzyme activity, glutathione peroxidase (GPX) were measured. Results show the efficacy of BT polyphenols to decrease DNA oxidative damage and to affect GPX activity (P<0.05), while no effect was shown on MDA production. The succeeding investigation of the activity of caffeine and epigallocatechin gallate demonstrated their antioxidant potential with respect to the cellular markers evaluated. In conclusion, this study supports the protective effect of BT against ferrous ions induced oxidative damage to DNA and the ability of BT to affect the enzyme antioxidant system of Jurkat cells.

Malondialdehyde production in Jurkat T cells subjected to oxidative stress.

OBJECTIVE: We investigated the relation between membrane lipid peroxidation, as evaluated by malondialdehyde (MDA), and oxidative stimuli in the Jurkat T-cell line and designed a cellular model to assess the antioxidant potential of compounds. METHODS: Jurkat T cells were subjected to different concentrations of Fe(2+) ions (from 25 to 150 micromol/L) or H(2)O(2) (from 0.1 to 5 mmol/L), and MDA was determined after separation in high-performance liquid chromatography of the adduct with thiobarbituric acid. MDA production also was investigated in cells supplemented with epigallocatechin gallate and genistein and subjected to Fe(2+) oxidative treatment. RESULTS: MDA production increased with the concentration of Fe(2+), whereas H(2)O(2) had no effect at any concentration. Oxidative stress for 15 min or 2 h produced similar MDA levels. The supplementation of epigallocatechin gallate partly prevented MDA production (about 40%, P < 0.05), whereas genistein exerted no preventive effect on lipid peroxidation. CONCLUSION: We propose this cellular model, consisting of Jurkat T cells subjected to 100 micromol/L of Fe(2+) for 15 min, to study the protective effect of antioxidant supplementation against membrane lipid peroxidation.

The validity of predicted body fat percentage from body mass index and from impedance in samples of five European populations.

OBJECTIVES: To test and compare the validity of a body mass index (BMI)-based prediction equation and an impedance-based prediction equation for body fat percentage among various European population groups. DESIGN: Cross-sectional observational study. SETTINGS: The study was performed in five different European centres: Maastricht and Wageningen (The Netherlands), Milan and Rome (Italy) and Tampere (Finland), where body composition studies are routinely performed. SUBJECTS: A total of 234 females and 182 males, aged 18-70 y, BMI 17.0-41.9 kg/m(2). METHODS: The reference method for body fat percentage (BF%(REF)) was either dual-energy X-ray absorptiometry (DXA) or densitometry (underwater weighing). Body fat percentage (BF%) was also predicted from BMI, age and sex (BF%(BMI)) or with a hand-held impedance analyser that uses in addition to arm impedance weight, height, age and sex as predictors (BF%(IMP)). RESULTS: The overall mean (+/-s.e.) bias (measured minus predicted) for BF%(BMI) was 0.2+/-0.3 (NS) and-0.7+/-0.3 (NS) in females and males, respectively. The bias of BF%(IMP) was 0.2+/-0.2 (NS) and 1.0+/-0.4 (P<0.01) for females and males, respectively. There were significant differences in biases among the centres. The biases were correlated with level of BF% and with age. After correction for differences in age and BF% between the centres the bias of BF%(BMI) was not significantly different from zero in each centre and was not different among the centres anymore. The bias of BF%(IMP) decreased after correction and was significant from zero and significant from the other centres only in males from Tampere. Generally, individual biases can be high, leading to a considerable misclassification of obesity. The individual misclassification was generally higher with the BMI-based prediction. CONCLUSIONS: The prediction formulas give generally good estimates of BF% on a group level in the five population samples, except for the males from Tampere. More comparative studies should be conducted to get better insight in the generalisation of prediction methods and formulas. Individual results and classifications have to be interpreted with caution.