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PubMed2006

Changes in hypothalamic-pituitary-adrenal function, body temperature, body weight and food intake with repeated social stress exposure in rats.

These present studies aimed to compare changes in hypothalamic-pituitary-adrenal (HPA) activity and body temperature in response to acute social defeat, to repeated social stress and to novel restraint after repeated stress, as well as to assess effects on metabolic parameters by measuring body weight gain and food and water intake. We found that social defeat produced a marked increase in both adrenocorticotrophic hormone and corticosterone compared to placement in a novel cage. Similarly, body temperature was also increased during social defeat and during 30 min of recovery from defeat. We then examined the effects of 6 days of repeated social stress and observed minimal HPA responses to repeated social stress compared to control rats. These neuroendocrine responses were contrasted by robust increases in body temperature during stress and during recovery from stress during 6 days of repeated stress. However, in response to novel restraint, repeatedly stressed rats displayed facilitated body temperature responses compared to controls, similar to our previous findings with HPA activity. Food intake was increased during the light period during which defeat took place, but later intake during the dark period was not affected. Repeated stress decreased body weight gain in the dark period but food intake was increased overall during the 6 days of repeated stress in the light period. As a result, repeated stress increased cumulative food intake during the light period in the stressed rats but these relatively small increases in food intake were unable to prevent the diminished total weight gain in repeatedly stressed rats. Overall, the results demonstrate that, although acute social defeat has similar effects on temperature and HPA activity, repeated exposure to social stress has divergent effects on HPA activity compared to body temperature and that dampened weight gain produced by repeated social stress cannot be fully explained by changes in food intake.

Adaptation, Physiological↗

PubMed1984

Effects of photoperiod and gonadectomy on food intake, body weight, and body composition in Siberian hamsters.

Two experiments examined the effects of gonadectomy, photoperiod, and melatonin treatment on food intake, body weight, and carcass composition in male and female Siberian hamsters (Phodopus sungorus sungorus). Gonadectomy caused small decreases in body weight in both sexes but did not affect food intake. In males the weight reduction was due to small (nonsignificant) decreases in all carcass components. Ovariectomy caused a significant reduction in carcass lipid but did not affect lean body mass. A short photoperiod (8 h light, 16 h dark, LD 8:6) caused significant weight losses in all animals except ovariectomized females. Daily melatonin injections (12.5 micrograms sc, 3 h before lights-out) also reduced body weight in males and females housed in a long photoperiod (LD 16:8). The photoperiod- and melatonin-induced weight losses were almost entirely due to decreases in carcass lipid; lean body mass was unaffected by either treatment. Although short photoperiods and melatonin treatments decreased food intake, these changes were preceded by a significant loss of body weight. Thus photoperiod induced changes in food intake may be a consequence of the changes in body weight, rather than vice versa. These findings indicate that photoperiod and melatonin have important effects on adipose tissue mass in both Siberian and Syrian hamsters, even though one species gains weight (Syrian) and the other loses weight (Siberian) in short photoperiods.

Adipose Tissue, Brown↗

PubMed1987

Body composition, not body weight, is related to cardiovascular disease risk factors and sex hormone levels in men.

To clarify the independent relationships of obesity and overweight to cardiovascular disease risk factors and sex steroid levels, three age-matched groups of men were studied: (i) 8 normal weight men, less than 15% body fat, by hydrostatic weighing; (ii) 16 overweight, obese men, greater than 25% body fat and 135-160% of ideal body weight (IBW); and (iii) 8 overweight, lean men, 135-160% IBW, but less than 15% fat. Diastolic blood pressure was significantly greater for the obese (mean +/- SEM, 82 +/- 2 mmHg) than the normal (71 +/- 2) and overweight lean (72 +/- 2) groups, as were low density lipoprotein levels (131 +/- 9 vs. 98 + 11 and 98 + 14 mg/dl), the ratio of high density lipoprotein to total cholesterol (0.207 +/- 0.01 vs. 0.308 +/- 0.03 and 0.302 +/- 0.03), fasting plasma insulin (22 +/- 3 vs. 12 +/- 1 and 13 +/- 2 microU/ml), and the estradiol/testosterone ratio (0.076 +/- 0.01 vs. 0.042 +/- 0.02 and 0.052 +/- 0.02); P less than 0.05. Estradiol was 25% greater for the overweight lean group (40 +/- 5 pg/ml) than the obese (30 +/- 3 pg/ml) and normal groups (29 +/- 2 pg/ml), P = 0.08, whereas total testosterone was significantly lower in the obese (499 +/- 33 ng/dl) compared with the normal and overweight, lean groups (759 +/- 98 and 797 +/- 82 ng/dl). Estradiol was uncorrelated with risk factors and the estradiol/testosterone ratio appeared to be a function of the reduced testosterone levels in obesity, not independently correlated with lipid levels after adjustment for body fat content. Furthermore, no risk factors were significantly different between the normal and overweight lean groups. We conclude that (a) body composition, rather than body weight per se, is associated with increased cardiovascular disease risk factors; and (b) sex steroid alterations are related to body composition and are not an independent cardiovascular disease risk factor.

Adult↗

PubMed1997

Prediction of low body weight at long-term follow-up in acute anorexia nervosa by low body weight at referral.

OBJECTIVE: The authors investigated the hypothesis that in acute anorexia nervosa a low body weight predicts a poor weight prognosis for the future. METHOD: The body mass indexes at referral of 272 female patients were examined in relation to the body mass indexes of these patients after a mean follow-up of 9.5 years. RESULTS: The overall correlation between body mass indexes at referral and at follow-up was r = 0.33. Despite this low correlation, the 100 patients with body mass indexes less than 13 kg/m2 at referral had low weights at long-term follow-up. Eleven of the 12 deceased patients were among these 100 patients, as were 24 of the 46 surviving patients whose body mass indexes were 17.5 kg/m2 or less at follow-up. CONCLUSIONS: For patients with anorexia nervosa, a body mass index less than 13 kg/m2 at referral indicates a substantial risk for chronic anorexia nervosa and death related to emaciation.

Acute Disease↗

PubMed1986

Total body electrical conductivity used to determine body composition in infants.

Total body electrical conductivity (TOBEC) has been introduced as a rapid, safe, and noninvasive method suitable for the estimation of fat-free mass. The instrument (EMME or TOBEC) operates on the principle that organisms placed in an electromagnetic field perturb the field to a degree that depends on the amount and volume of distribution of electrolytes present. A study was designed to measure body composition in infants by the TOBEC method and to compare the results with those obtained using the isotope dilution technique. Sixteen infants (age range, 2 days to 9.7 months; weight range, 2 to 8.7 kg) were enrolled. Total body water (TBW) was determined by the isotope dilution technique using H218O. There was a good correlation between the natural logarithm of the TOBEC number and TBW, with a linear correlation coefficient of 0.949. The fat-free body mass of the infants was calculated by TBW (fat-free body mass = /0.082) and by the TOBEC method using the standard previously derived from mature rabbits. TBW measurements by H218O dilution appeared to overestimate fat-free mass which was greater than TBW in five of the 16 infants. Measured by the TOBEC method, fat-free mass ranged from 51 to 91% of total body weight. The TOBEC method is highly suitable for use with human infants and appears to determine body composition as accurately as other available methods.

Body Composition↗

PubMed2001

Body mass index, body composition, and leptin at onset of puberty in male and female rats after intrauterine growth retardation and after early postnatal food restriction.

In this study we examined the body composition at onset of puberty in intrauterine growth retarded (IUGR), postnatal food restricted (FR), and control male and female rats. IUGR was induced by ligation of the uterine artery on d 17 of gestation and FR by litter enlargement to 20 pups per mother from d 2 after birth until weaning (d 24). We defined onset of puberty as balanopreputial separation in male rats and vaginal opening in female rats. We calculated body mass index, measured body composition with dual-energy x-ray absorptiometry, and measured leptin concentrations in serum. It was reported previously that early malnutrition, either during late gestation or immediately postnatally, results in a delayed onset of puberty in IUGR and FR male rats and in IUGR female rats, but not in FR female rats. In IUGR male rats at balanopreputial separation and in IUGR female rats at vaginal opening no differences were found in body mass index, body composition, and leptin levels compared with controls. FR male rats had a significantly lower percentage of fat and serum leptin concentrations at balanopreputial separation. FR female rats had a significantly lower body mass index, percentage of fat, and serum leptin concentrations at vaginal opening. We conclude that the onset of puberty in the rat is not dependent on a certain percentage of body fat or a certain threshold of circulating levels of leptin and that food deprivation during different "critical" time periods around birth results in different effects in later life.

Animals↗

PubMed2001

The relationship of Chironomus riparius larval Se body burden and body concentration to larval dry mass and effects on sensitivity to selenium.

Selenium as selenite was added to laboratory cultures of Chironomus riparius. In two sets of cultures, substrate-bound Se concentrations were typically 10(3) times dissolved Se concentrations, while in the other set dissolved Se concentrations were about 10 to 50 times substrate-bound Se concentrations. Body burdens of individual second-, third-, and fourth-instar larvae and eviscerated fourth-instar larvae were measured. Regressions of Se body burden on larval dry mass found evidence for separate intercepts but common slopes for each instar, and Se body concentrations were diluted by growth. The derivation of body concentration from body burden as a function of larval dry mass was used to derive a model of body burden and body concentration as a function of instar. Toxicity tests were performed to check for a change in sensitivity to Se as a function of culture Se concentration. Larval Se concentrations were highly correlated with dissolved Se concentrations but not with substrate-bound Se concentrations. Increases in Se in substrate caused no sensitization, while increases in dissolved Se caused desensitization. We concluded that covariates such as larval dry mass should be incorporated when deriving water quality criteria.

Animals↗

PubMed2003

Heritability of body length and measures of body density and their relationship to backfat thickness and loin muscle area in swine.

The objective of this study was to estimate heritability for body length (LEN) at the end of performance testing and to estimate genetic correlations with backfat (BF) thickness and loin muscle area (LMA) in Landrace, Yorkshire, Duroc, and Hampshire breeds of swine. Also examined were two measures of body density involving body length and weight and their relationships to backfat and loin muscle area. Data consisted of performance test records collected in a commercial swine operation from 1992 to 1999. Boars from 60% of the litters were culled at weaning based on a maternal breeding value of the dam. Remaining boars and all females were grown to 100 d of age (15,594, 55,497, 12,267, and 9,782 Landrace, Yorkshire, Duroc, and Hampshire pigs, respectively). At this time, all pigs were weighed (WT100) and selected for performance testing based on a combination of maternal and performance indexes, which differed by breed. All pigs were weighed at the end of the 77 d performance test (WT177) when BF, LMA, and LEN were measured. Two measures of body density involving length were calculated: Body mass index (BMI) = WT177/LEN2 and body density (DENSITY) = WT177/LEN. For each breed, genetic parameters were estimated using an animal model with random litter effects and multiple-trait REML procedures. A series of three-trait models including WT100 and combinations of two other traits in each analysis was conducted. Fixed effects included contemporary group and age as a covariate. Average estimates of heritability were 0.16 to 0.32 for LEN (unadjusted for WT177), 0.12 to 0.26 for LEN (adjusted for WT177), 0.23 to 0.33 for DENSITY, and 0.16 to 0.25 for BMI. Genetic correlations between LEN and LMA were low. Genetic correlations between LEN (unadjusted for WT177) and BF were 0.10 to 0.41. Adjusting LEN for WT177 gave correlations of 0.11 for Landrace and Hampshire and negative correlations (-0.06 and -0.19, respectively) for Yorkshire and Duroc. Genetic correlations between LMA and DENSITY and between LMA and BMI were comparable and ranged from 0.44 to 0.54. Genetic correlations between BF and DENSITY were slightly higher (0.53 to 0.68) than those between BF and BMI (0.37 to 0.67). In these data, not much relationship between BF and body length at a constant weight and age was found. There was a negative relationship between LMA and LEN at a constant weight and age, implying that longer pigs had smaller LMA.

Adipose Tissue↗

PubMed2006

Body composition of breeding gilts in response to dietary protein and energy balance from thirty kilograms of body weight to completion of first parity.

The relationships among BW, backfat depth, and body physical and chemical composition were evaluated in response to dietary protein and DE balance in breeding gilts from 30 kg of BW to weaning of the first litter. Large White (sire) x Landrace (dam) F1 hybrid (White; n = 75) and Landrace (sire) x (Meishan x Large White; dam) (Meishan; n = 19) hybrid gilts were received at 30 kg of BW. Five gilts were taken as the initial slaughter group at 30 kg of BW, and the remaining gilts were fed diets differing in total lysine to DE ratio, high (H) vs. low (L), from 30 kg of BW to mating (rearing), and during gestation and lactation, allowing factorial investigation of dietary treatment effects and interactions during rearing, gestation, and lactation. Gilts were slaughtered at approximately 50 and 90 kg of BW, and at mating, farrowing, and weaning. Gilts fed L diets during rearing were lighter at mating (117.9 vs. 133.6 kg of BW, P = 0.035) due to a reduction in gain (592 vs. 720 g/d, P = 0.002) and a restriction in protein accretion (83 vs. 117 g/d, P = 0.001). During rearing, lipid accretion did not differ between L- and H-fed gilts (208 vs. 198 g/d, P = 0.60), but the ratio of lipid to protein accretion was about 1.5-fold greater in L-fed gilts, where lipid mass expressed as a percentage of BW was increased at mating (26.0 vs. 21.9%, P = 0.005). Effects of L diets on lipid accretion during rearing were transient; no residual effects on body lipid mass (P > 0.17) were found at farrowing or weaning. Overall, Meishan hybrids carried greater lipid mass (P < 0.001) than White hybrid gilts. Whereas the rate of body lipid and protein accretion and body lipid and protein mass can be nutritionally influenced and can vary according to growth stage, reproductive status, and genotype, this study established that body protein mass expressed as a proportion of the lipid free empty BW remains inflexible. A value for this measure of 0.188 +/- 0.0052 was found in White and Meishan hybrid gilts ranging from 28 to 203 kg of BW and 3 to 36 mm backfat depth, covering growth, pregnancy, and lactation, and offered diets differing in protein and energy balance. Body protein mass can be predicted as approximately 0.2 of the lipid free empty BW once body lipid mass is estimated accurately from physical measurements, such as backfat depth (P2, mm) and BW (kg), by regression using lipid (kg) = - 8.14 (SE, 1.302) + 0.167 (SE, 0.010) BW + 0.883 (SE, 0.065) P2 (residual SD = 3.51; R2 = 0.912).

Aging↗

PubMed2002

Association between body composition and body mass index in young Japanese women.

The National Nutrition Survey of Japan indicated a trend toward a decreasing body mass index (BMI; kg/m2) among young Japanese women. Current studies suggest that not-high BMI often does not correlate with not-high body fat percentage. Recently, the classification of BMI in adult Asians was proposed by the International Obesity Task Force. The addition of an "at risk of overweight" category, BMI as 23.0-24.9, was intended to prevent chronic diseases. We investigated the association between body fat percentage (BF%) and BMI to evaluate the screening performance of BMI focused on individual preventive medicine. The subjects consisted of 605 female college students. The subjects' ages (y), heights (cm), body weights (kg), BMIs, and BF percents with underwater weighing expressed as the means +/- SD were 19.6 +/- 0.5, 158.7 +/- 5.6, 53.8 +/- 7.2, 21.3 +/- 2.4, and 24.9 +/- 4.9, respectively. We defined high BF% as +/- 85th percentile of BF% (29.8%). High-BF% individuals are often not classified into BMI > or = 23.0 because their BMI readings are very broad (18.4-31.7). In comparison to the screening performances (specificity and sensitivity), BMI > or = 23.0 (85.3% and 52.1%, respectively), rather than BMI > or = 25.0 (96.7% and 29.8%, respectively), is recommended for the mass evaluation of fatness. For this reason, the BMI "at risk of overweight" category is characterized as the threshold of increasing the appearance ratio of high-BF% individuals. In conclusion, the BMI > or = 25.0 kg/m2 category is determined as high BF%, regardless of body composition measurement for mass evaluation as a result of quite high specificity. Even so, body composition measurement is necessitated by the individual evaluation of fatness focused on preventive medicine because BMI performed a poor representation of body composition, especially BMI < 25.0 kg/m2 individuals.

Adipose Tissue↗

PubMed2003

Effects of metal implants on whole-body dual-energy x-ray absorptiometry measurements of bone mineral content and body composition.

OBJECTIVE: The purpose of this study was to evaluate the influence of metal implants on measurements of bone mineral content and body composition by x-ray-based dual-photon absorptiometry. METHODS: Four whole-body dual-photon absorptiometry scans were performed on 13 participants with metal rods either present or absent during the scans. The influence of the amount of metal (50 g, 100 g and 150 g), the proximity of the metal rod to the x-ray source and the reproducibility of any metal-induced effects were evaluated by altering the position or the size of the metal rod used, or both. RESULTS: The presence of metal rods weighing 100 g or 150 g significantly increased reported total body mass and bone mineral content (p < 0.034). Soft-tissue mass was increased when the scan included the 100-g rod (p < 0.003). The proximity of the metal to the x-ray source did not have a significant influence on the body composition changes induced by the metal. The effects of the metal rods on body composition variables were reproducible. CONCLUSION: The presence of metal rods inflated body composition variables measured by dual-photon absorptiometry; however, the effects are reproducible during repeat scans of an individual patient. Metal had the largest impact on whole-body bone mineral content, causing errors of 1.5%-3%.

Absorptiometry, Photon↗

PubMed1992

Body mass index, body composition and the chronic energy deficiency classification of rural adult populations in Guatemala.

The present study tested the hypotheses that: (a) individual body composition estimates obtained with the Durnin-Womersley (D-W) equations have low validity in certain populations in developing countries; (b) there exists a poor relationship between the body mass index (BMI) and body composition estimates (fat mass (BFM) and fat-free mass (FFM)), and (c) BMI cut-off estimates (fat mass (BFM) and fat-free mass (FFM)), and (c) BMI cut-off points provide an invalid classification of chronic energy deficiency (CED) in adults. The study involved four samples of rural men and women in Guatemala, who had mean BMI of approximately 21 kg/m2. Body composition estimates were obtained by densitometry in three of the samples. Mean body fat (%) and mean FFM (kg) were: men: 11.6 (+/- 4.7) and 47.7 (+/- 4.9); and women: 21.6 (+/- 5.3) and 35.8 (+/- 3.5), respectively. The D-W equations based on various combinations of skinfold measurements consistently overestimated body fat content with low precision and validity. The BMI was more related to BFM and FFM than to fat proportion, but explained little of the variation in both body components, particularly at low BMI levels. A small number of men and women had BMI values below 18.5 kg/m2, and only one woman fell below 16 kg/m2. The power coefficients of height in the weight/height ratio which provided the strongest correlations with BFM and FFM were: BFM: women: 1.0; men: 1.5; FFM: 0.5 for both women and men. We conclude that the Quetelet index should not be recommended as a universally valid indicator to classify CED in adult groups similar to the study population.

Adipose Tissue↗

PubMed2006

Relationship between bone and ash weight to age, body weight and body length of thai adults after cremation.

BACKGROUND: Cremation is the most common Thai funeral mode. In Thailand, there have not been any previous reports of bone and ash weight after cremation. OBJECTIVE: Collect the bone and ash weight after the cremation and find the variables that affected the bone and ash weight. MATERIAL AND METHOD: One hundred and ten samples, including fifty-five males and fifty-five females, were collected from the Thai population. A Thai crematorium (Series Tiger 1) that could produce a temperature of approximately 850 degrees C - 1200 degrees C was employed. It took about 1-1.5 hours to complete the incineration. RESULTS: The average bone and ash weight of the males was 2.68 kg with SD 1.41; female was 2.12 with SD 1.25; and total was 2.40 with SD 1.36. The present study supported that age and body weight affected the bone and ash weight while the body length (height) did not. The fitted equation was y = 1.969 - 0.01846 (age) + 0.03087 (body weight), where y = predicted bone and ash weight. CONCLUSION: The present study shows that age and body weight affected the bone and ash weight. From this information, the authors could find the predicted value of either age or body weight. If the authors would like to find the age, the authors can employ the fittest equation y = 76.097 - 3.219 (Bone and ash weight) where y = predicted age. Additionally, if the authors would like tofind the body weight, we can employ thefittest equation = 51.930 + 1.673 (Bone and ash weight) where y = predicted body weight.

Adolescent↗

PubMed1990

Plasma lipids and apoproteins, body fat distribution and body fatness in early pubertal children.

Besides body fatness, the body fat distribution is associated with coronary risk in adults, but little has been reported on this aspect in children. This study describes body fatness, body fat distribution (waist-to-hip ratio, WHR) and the plasma lipid and apoprotein profile (TC, HDL-C, LDL-C, TG, apo A-I and apo B) in 60 boys (age 10.8 +/- 0.1 year; mean +/- s.e.m.) and 64 girls (age 10.2 +/- 0.1 year), all caucasian. To avoid interference by the large changes in plasma sex hormone levels during puberty, only pre- and early pubertal children (Tanner stages of genital c.q. breast development 1 or 2) participated. Physical and sports activity was scored in hours per week using a questionnaire. The boys were taller than the girls (146.2 +/- 0.7 vs 143.2 +/- 0.9 cm; ANOVA, P less than or equal to 0.05) and their WHR was larger (0.88 +/- 0.01 vs 0.83 +/- 0.01; ANOVA, P less than or equal to 0.05). The boys spent 8.0 +/- 0.4 hours weekly on physical and sports activities, the girls 5.5 +/- 0.3 (ANOVA, P less than or equal to 0.05). The plasma lipid and apoprotein profiles were similar in both groups. Body fatness was significantly associated with the lipid and apoprotein profile, although in different ways in boys and girls. In boys there was a relationship with TG (r = 0.49), with apo B (r = 0.33) and with the apo A-I to apo B ratio (r = -0.24); in girls with TG (r = 0.25), HDL-C (r = -0.39), apo A-I (r = -0.28) and with the HDL-C to TC ratio (r = -0.31); P less than 0.05 for all correlations. A regional component of the subcutaneous fatmass, assessed by the partial correlations of the individual skinfold thicknesses with the plasma lipid and apoprotein profile after controlling for body fatness, was lacking in these early and prepubertal children. The WHR was associated with TC (r = 0.35), LDL-C (r = 0.32), apo B (r = 0.36) and with apo A-I/apo B (r = -0.34) in the girls after controlling for body fatness. Although closer investigation into the validity of the WHR as a measure of fat distribution in children is needed, the tentative conclusion is that in pre- and early pubertal girls the WHR has an impact on the plasma lipid and apoprotein profile similar to that seen in adults. It is suggested that in boys these relationships develop later in puberty.

Adipose Tissue↗

PubMed1987

Predictive value of the index of desirable body weight for total body fat mass as measured by dilution of tritiated water--problems and limitations.

The index of desirable body weight is currently used for classification of patients' weights. We examined how it is related to the degree of adiposity, and whether it can serve in the prediction of body fat to the same degree as Quetelet's index. Sixty-five women and 142 men comprising a wide range of weight indices were studied. Body fat (F) was measured by the tritium dilution technique with a precision of +/- 1.26 kg. Regressions of F/W0 on the index of desirable weight W/W0 gave a correlation coefficient of 0.969 for women and 0.939 for men. Regressions of F/H2 on Quetelet's index W/H2 had correlation coefficients of the same order, i.e. 0.971 for women and 0.936 for men. Hence both indices are equally powerful for calculation of body fat within the study population. Further progress was achieved by multiple regression of F on W and W0 which yielded correlation coefficients of 0.976 for women and 0.953 for men. The residual standard deviation reflecting the mean difference between calculated and estimated fat was 3.4 kg for women and 3.8 kg for men. Despite this self-consistency, prediction of body fat for persons outside the study population is only possible within wide limits. These are given by about twice the residual standard deviation. Therefore, prediction of body fat from weight indices can only be used for detection of larger abnormalities in body composition.

Adult↗

PubMed1965

Body composition and body weight: criteria of overnutrition.

The terms "body weight" and "body composition" are by no means synonymous, and attention is increasingly being focused on body composition. A measurement of relative fatness is a better criterion of caloric overnutrition than is body weight.The simple technique of skinfold measurement using established standard methods is the most practical for use in the field to obtain an estimate of fatness or caloric overnutrition. The current need is for the establishment of "norms" for skinfolds for population groups of all ages and both sexes. When these are established, excellent simple criteria for overnutrition will be available.Prior to the establishment of norms, more work is needed to indicate which skinfolds for each age group and for each sex best reflect total body fatness. Body fatness may then be studied in relation to body weight and both may be related to morbidity, mortality and longevity. Finally, the answer may be obtained to the question whether it is overweight per se or overfatness that is related to excess morbidity and mortality.

Adolescent↗

PubMed1994

Population differences in body composition in relation to the body mass index.

This paper examines the relationships between body mass index (BMI) and body composition in different population groups where low BMIs might be expected to occur and assesses the extent to which BMIs are influenced by size and shape. The relationship between BMI and fat as a percentage of body weight is approximately linear although theoretically a curvilinear relationship is to be expected. However, by allowing for a variable composition of weight differences, an approximately linear theoretical relationship is obtained. There are few direct data (e.g. from densitometry, hydrometry etc.) on body composition in the groups in question and to examine the relationships indirect data were used. The regression coefficients of fat-free mass on BMI for 285 samples of Africans, people of Asian origin, Indo-Mediterraneans and Pacific people were not significantly different in the various groups of each sex; % fat on BMI was similarly related in four groups of women. Intercept terms were all significantly different. Using the sitting height-to-stature ratio (SH/S) as an index of body shape in 158 groups, the regression coefficient of BMI on SH/S was 0.90 kg/m2 per 0.01 SH/S. Mean SH/S lies between 0.50 and 0.55 in most populations so that shape could affect BMI by 5 kg/m2 and influence markedly the interpretation of BMI. However, allowing for SH/S is not straightforward as there is as much variation within as between groups. In conclusion, low BMI approximates to low weight, fat mass and fat-free mass. There are differences in the relationships of BMI to body composition but over the range 20-25 kg/m2 these may not be important in epidemiological studies. To interpret BMI in terms of body composition in more detail it is necessary to take into account sex, age, shape and ethnicity.

Adipose Tissue↗

PubMed1995

Familial clustering of multiple measures of adiposity and fat distribution in the Québec Family Study: a trivariate analysis of percent body fat, body mass index, and trunk-to-extremity skinfold ratio.

OBJECTIVE: To assess whether independent or common (pleiotropic) familial factors (i.e., genetic and/or common environment) underlie the observed associations among measures of body mass, body fat, and its distribution. DESIGN: A familial correlation model involves both parents and offspring, and gives rise to three types of familial correlations (spouse, parent-offspring, and sibling). A pattern of significant familial correlations suggests that the trait is determined by familial factors (i.e., genetic and/or environmental heritability). Cross-trait familial correlations are also estimated, both within individuals (intraindividual) and between family members (interindividual). Interindividual cross-trait familial correlations (e.g., trait 1 in parents with trait 2 in offspring) lead to the same type of familial inferences regarding bivariate heritabilities. SUBJECTS AND MEASURES: Measures of total body fat (% body fat-%BF), fat distribution (trunk/extremity skinfold ratio-TER), and body mass index (BMI) were assessed in 1239 individuals from 309 nuclear families participating the Québec Family Study. RESULTS: All three adiposity measures are cross-correlated within individuals. However, interindividual cross-trait correlations, which alone are capable of suggesting common familial determinants, are significant only for BMI with each of %BF and TER (bivariate heritabilities of 10% and 18%, respectively), and not for %BF and TER. CONCLUSION: Although all three adiposity measures are correlated within individuals, there appear to be entirely different underlying genes and/or environmental factors influencing the adiposity phenotypes of total body fat and fat distribution. The BMI, however, apparently shares some familial determinants with both total body fat and fat distribution.

Adolescent↗