Prevalence of obesity and the relationship between the body mass index and body fat: cross-sectional, population-based data

Background

Anthropometric measures such as the body mass index (BMI) and waist circumference are widely used as convenient indices of adiposity, yet there are limitations in their estimates of body fat. We aimed to determine the prevalence of obesity using criteria based on the BMI and waist circumference, and to examine the relationship between the BMI and body fat.

Methodology/Principal Findings

This population-based, cross-sectional study was conducted as part of the Geelong Osteoporosis Study. A random sample of 1,467 men and 1,076 women aged 20–96 years was assessed 2001–2008. Overweight and obesity were identified according to BMI (overweight 25.0–29.9 kg/m²; obesity ≥30.0 kg/m²) and waist circumference (overweight men 94.0–101.9 cm; women 80.0–87.9 cm; obesity men ≥102.0 cm, women ≥88.0 cm); body fat mass was assessed using dual energy X-ray absorptiometry; height and weight were measured and lifestyle factors documented by self-report. According to the BMI, 45.1% (95%CI 42.4–47.9) of men and 30.2% (95%CI 27.4–33.0) of women were overweight and a further 20.2% (95%CI 18.0–22.4) of men and 28.6% (95%CI 25.8–31.3) of women were obese. Using waist circumference, 27.5% (95%CI 25.1–30.0) of men and 23.3% (95%CI 20.8–25.9) of women were overweight, and 29.3% (95%CI 26.9–31.7) of men and 44.1% (95%CI 41.2–47.1) of women, obese. Both criteria indicate that approximately 60% of the population exceeded recommended thresholds for healthy body habitus. There was no consistent pattern apparent between BMI and energy intake. Compared with women, BMI overestimated adiposity in men, whose excess weight was largely attributable to muscular body builds and greater bone mass. BMI also underestimated adiposity in the elderly. Regression models including gender, age and BMI explained 0.825 of the variance in percent body fat.

Conclusions/Significance

As the BMI does not account for differences in body composition, we suggest that gender- and age-specific thresholds should be considered when the BMI is used to indicate adiposity.     

白头鹎体温、体重及能量代谢的昼夜节律

动物的生理昼夜节律是对环境昼夜变化的一种重要适应。为探讨白头鹎(Pycnonotus sinensis)体温、体重及能量代谢的昼夜节律变化,采用数字式温度计、电子天平及封闭式流体压力呼吸仪,测定了白头鹎的日体温、日体重和昼夜基础代谢率(BMR)。结果发现:白头鹎日体温及日体重变化存在显著差异,其中夜间体温明显低于白昼,并在4:00时体温呈现最低值;而白头鹎夜间体重显著低于白昼,在4:00时达到最小值,在18:00时达到最大值。另外,白头鹎的BMR也表现出了明显的昼夜差异,夜间BMR显著低于白昼。表明白头鹎体温、体重及能量代谢存在显著的昼夜节律变化,并调节达到自身生理能量平衡,从而适应昼夜环境变化。     

Food web structure and body size: trophic position and resource acquisition

Ulrich Brose Body size is recognized as an important determinant of trophic structure as it affects individual energetic demands, population density, and the interaction between potential prey and predators. However, its relationship with trophic position remains unclear. It has been hypothesized that a positive relationship between body size and trophic position would be associated to some particular trophic structures, which would allow larger organisms to satisfy their energetic demand and sustain viable population sizes at higher trophic positions, where fewer resources are available. To test this hypothesis, we analyzed the diet of 619 killifishes from four species (Austrolebias cheradophilus, A. luteoflammulatus, A. viarius and Cynopoecilus melanotaenia), collected in temporary ponds occurring in the grasslands of Rocha, Uruguay. Trophic position, diet richness, number of energy sources, and evenness were estimated for 20 size classes, formed by consecutive groups of 31 individuals. Gape limitation and preference for the larger available prey were evaluated as explanations for observed patterns with an individual based model (IBM). In agreement with the hypothesis, killifishes presented a strong positive relationship between trophic position and body size (R²=0.86), associated with a trophic structure that could allow larger organisms to have access to more energy from the environment. This was reflected in a positive relationship between body size and 1) prey richness, 2) number of basal energy sources (i.e. plants, detritus, phytoplankton and terrestrial prey), and 3) evenness in prey use. IBM results showed that changes in trophic structure with body size are well explained by gape limitation, but not by size preferences. Our results suggest that the fulfilment of the greater energetic demands of larger organism will depend on community diversity, which typically increases with ecosystem size, indicating a novel connection between area, diversity, body size, and food chain length.     

The linear allometric relationship between total metabolic energy per life span and body mass of mammals

The aim of this study is to establish and calculate the exact allometric relationship between the total metabolic energy per life span and the body mass in a wide range of mammals with about six orders of magnitude variation of the body mass of animals. The study shows that it exists a linear relationship between the total metabolic energy per life span PT(ls) (kJ) and the body mass M (kg) of 95 mammals (3 monotremes, Subclass Prototheria, 16 marsupialis (Subclass Theria, Infraclass Metatheria) and 76 placentals (Subclass Theria, Infraclass Eutheria)) from type: PT(ls)=A(ls)(+)M(1.0511), where P (kJ/day) is the basal rate of metabolism and T(ls) (days) is the mean life span of animals. The linear coefficient A(ls)(+)=7.158x10(5) kJ/kg is the total metabolic energy, exhausted during the life span per 1 kg body mass of the animals. The mean values of the total metabolic energy per life span, per unit body mass (A(ls)) for orders from Subclass Prototheria and Theria (Infraclass Metatheria) and orders Xenarthra, Pholidota, Soricomorpha, Rodentia (Infraclass Eutheria) varied negligible in interval (4.656-5.80)x10(5) kJ/kg. The coefficient A(ls) grows from (7.68-8.36)x10(5) kJ/kg in Lagomorpha and Artiodactyla (Eutheria) to (10.58-12.64)x10(5) kJ/kg in orders Carnivora, Pinnipeda and Chiroptera (Eutheria). A(ls) grows maximum to 18.5x10(5) kJ/kg in Primates. Thus, the values of coefficient A(ls) differ maximum four-fold in all orders. Across the all species the values of A(ls) are changes about one order of magnitude. Consequently, our survey shows that the changes of the body mass, basal metabolic rate and the life span of animals are three mutually related parameters, so that the product A(ls)=(PT(ls))/M remains relatively constant in comparison to 1 million fold difference in body mass and total metabolic energy per life span between mammals.     

Resting energy expenditure-fat-free mass relationship: new insights provided by body composition modeling

The relationship between resting energy expenditure (REE) and metabolically active fat-free mass (FFM) is a cornerstone in the study of physiological aspects of body weight regulation and human energy requirements. Important questions, however, remain unanswered regarding the observed linear REE-FFM association in adult humans. This led us to develop a series of REE-body composition models that provide insights into the widely used simple linear REE-FFM prediction model derived experimentally in adult humans. The new models suggest that the REE-FFM relationship in mammals as a whole is curvilinear, that a segment of this function within a FFM range characteristic of adult humans can be fit with a linear equation almost identical to that observed from a composite review of earlier human studies, and that mammals as a whole exhibit a decrease in the proportion of FFM as high metabolic rate organs with greater FFM. The present study thus provides a new approach for examining REE-FFM relationships, advances in a quantitative manner previously observed albeit incompletely formulated REE-body composition associations, and identifies areas in need of additional research.     

On the relationship between body dimensions and appendix length

In the last decades a lot of significant correlations between clinical and anthropometric parameters were found, e.g. the relationships between somatotypical and endocrine parameters or between body dimensions and echocardiographic heart size. During operation, surgeons often find a wide range of appendix size of patients with varying body dimensions. A goal of this work is the detection of the relationships between anthropometric characteristics (height, weight, body mass index (= BMI)), inflammation parameters (histological inflammation degree, leukocyte count and C-reactive protein (= CRP)) and the appendix length with n=167 consecutive patients (time period 1.1.2004 - 31.12.2006; range of age 7-95 years, median age 20 years; average age of men 27.7, women 26.6 years), which had to be operated because of acute appendicitis. Appendectomy was laparoscopic in 95 % of the patients and open in 5 %. The appendix length of the male patients was high-significantly longer with a mean of 7.5 cm (SD = 2.1) than those of the female patients with 6.3 cm (SD = 1.6). The following mean anthropometric values were registered: height 169.8 (SD = 15.6) cm for the males and 165.2 (SD = 9.6) cm for the females, weight 70.4 (SD = 23.4) kg for the males and 61.9 (SD = 16.1) kg for the females, BMI 24.1 (SD = 5.4) kg/m2 for the males and 22.9 (SD = 4.8) kg/m2 for the females. The mean leukocyte count was 12,700 (SD = 5500)/ml for the males and 11,600 (SD = 4900)/ml for the females, CRP was 4.3 (SD = 5.4) mg/l for the males and 4.5 (SD = 8.9) mg/l for the females. Concerning the histopathological diagnosis, n=76 patients (45.5 %) suffered from a submucous fibrosis bliteration, n 1 (12.6 ) from an acute purulent inflammation degree, n = 65 (38.9 ) from an ulcerative hlegmonous inflammation degree and n (3 ) from a perforation. While no significant Spearman's correlation coefficient between appendix length and CRP was found, the appendix length correlated highly significantly to the body weight (r = 0.25) and significantly to leukocyte count (r = 0.16), body height (r = 0.16), BMI (r = 0.17) and the histological inflammation degree (r = 0.18). Thus, the correlations found were lower than the relationships between anthropometric and endocrine or echocardiographic parameters described in literature.     

Modeling the relationship between body weight and energy intake: A molecular diffusion-based approach

ABSTRACT: BACKGROUND: Body weight is at least partly controlled by the choices made by a human in response to external stimuli. Changes in body weight are mainly caused by energy intake. By analyzing the mechanisms involved in food intake, we considered that molecular diffusion plays an important role in body weight changes. We propose a model based on Fick's second law of diffusion to simulate the relationship between energy intake and body weight. RESULTS: This model was applied to food intake and body weight data recorded in humans; the model showed a good fit to the experimental data. This model was also effective in predicting future body weight. CONCLUSIONS: In conclusion, this model based on molecular diffusion provides a new insight into the body weight mechanisms.     

Biomechanical evaluation of the relationship between postural control and body mass index

Postural stability is crucial in maintaining body balance during quiet standing, locomotion, and any activities that require a high degree of balance performance, such as participating in sports and dancing. Research has shown that there is a relationship between stability and body mass. The aims of this study were to examine the impact that two variables had on static postural control: body mass index (BMI) and gender. Eighty healthy young adults (age=21.7±1.8 yr; height=1.65±0.09 m; mass=67.5±19.0 kg) participated in the study and the static postural control was assessed using the Biodex Balance System, with a 20 Hz sampling rate in the bipedic stance (BLS) and unipedic stance (ULS) for 30s. Five test evaluations were performed for each balance test. Postural control was found to be negatively correlated with increased adiposity, as the obese BMI group performed significantly poorer than the underweight, normal weight and overweight groups during BLS and ULS tests. The underweight, normal weight and overweight groups exhibited greater anterior-posterior stability in postural control during quiet stance. In addition, female displayed a trend of having a greater postural sway than male young adults, although it was evidenced in only some BMI groups. This study revealed that BMI do have an impact on postural control during both BLS and ULS. As such, BMI and gender-specific effects should be taken into consideration when selecting individuals for different types of sporting activities, especially those that require quiet standing.     

Interplay between temperature,fish partial migration and trophic dynamics

Whereas many studies have addressed the mechanisms driving partial migration, few have focused on the consequences of partial migration on trophic dynamics, and integrated studies combining the two approaches are virtually nonexistent. Here we show that temperature affects seasonal partial migration of cyprinid fish from lakes to predation refuges in streams during winter and that this migration in combination with temperature affects the characteristics and phenology of lower trophic levels in the lake ecosystem. Specifically, our six‐year study showed that the proportion of fish migrating was positively related to lake temperature during the pre‐migration growth period, i.e. during summer. Migration from the lake occurred later when autumn water temperatures were high, and timing of return migration to the lake occurred earlier at higher spring water temperatures. Moreover, the winter mean size of zooplankton in the lake increased with the proportion of fish being away from the lake, likely as a consequence of decreased predation pressure. Peak biomass of phytoplankton in spring occurred earlier at higher spring water temperatures and with less fish being away from the lake. Accordingly, peak zooplankton biomass occurred earlier at higher spring water temperature, but relatively later if less fish were away from the lake. Hence, the time between phyto‐ and zooplankton peaks depended only on the amount of fish being away from the lake, and not on temperature. The intensity of fish migration thereby had a major effect on plankton spring dynamics. These results significantly contribute to our understanding of the interplay between partial migration and trophic dynamics, and suggest that ongoing climate change may significantly affect such dynamics.     

The relationship between body mass index, semen and sex hormones in adult male

This study was aimed at evaluating the relationship between body mass index, sex hormones and semen characteristics in male adults. 120 male adults aged 20 to 50 years who consented to participate in the study were used. Serum samples collected from each subject were analyzed for Luteinizing hormone (LH), Follicle stimulating hormone (FSH), Prolactin (PRL), Progesterone, Estradiol and testosterone by classical ELISA method. Semen samples obtained by masturbation after 72 hours of abstinence were analyzed for sperm count and motility. The results showed statistically significant correlations at 99% confidence level between body mass index and serum concentrations of progesterone and oestradiol and sperm count. No significant correlations were observed between body mass index and sperm motility, serum concentrations of prolactin, testosterone and luteinizing hormone. In conclusion, this study has shown that statistically significant correlations exist between body mass index, semen characteristics and male sex hormones and may broaden our understanding of the physiology of male fertility/infertility. Keywords: Body mass index, Semen quality, Male sex hormones, Fertility/infertility.     

Dose-response relationship between body temperature and birth defects in radiofrequency-irradiated rats

Five groups of pregnant Sprague-Dawley rats were irradiated for 10-40 min on gestation day 9 in a 27.12-MHz radiofrequency field at a magnetic field strength of 55 A/m and an electric field strength of 300 V/m. The specific absorption rate was 10.8 +/- 0.3 W/kg. Exposures were terminated after the rat's colonic temperature reached 41.0 degrees C, 41.5 degrees C, 42.0 degrees C, 42.5 degrees C, or 43.0 degrees C. A control group was sham irradiated at 0 A/m and 0 V/m on gestation day 9, whereas a second control group was untreated. The incidence of both birth defects and prenatal death was directly related to maternal body temperature once a temperature threshold was exceeded. The temperature threshold for both types of effects was approximately 41.5 degrees C. A few pregnant rats died after exposure to 43.0 degrees C, and higher temperatures were nearly always lethal.     

Allometric relationship between body mass and aerobic metabolism in zebrafish Danio rerio

The relationship between body mass (M) and metabolic rate was investigated through the assessment of active (R_A) and standard (R_S) metabolic rate at different life stages in zebrafish Danio rerio (5 day‐old larvae, 2 month‐old juveniles and 6 month‐old adults). Scaling exponents and constants were assessed for standard (R_S = 0·273M^0·965 in mgO₂ g^?1 h^?1) and active metabolic rate (R_A = 0·799M^0·926 in mgO₂ g^?1 h^?1). These data provide the basis for further experiments regarding the effects of environmental factors on aerobic metabolism throughout the life cycle of this species.     

The relationship between body mass and relative investment in testes mass in amniotes and other vertebrates

In terrestrial placental mammals, there is a well‐known negative allometric relationship between body mass and relative investment in testes mass. Such a negative relationship means that males of relatively monogamous small species invest proportionately more in their reproductive tissues than males of more polyandrous larger species. The selective pressure responsible for this relationship remains unclear and is it not known if this is a general allometric relationship that is similar across all vertebrate lineages. To investigate this, we conducted the first comparison of relationships between body mass and testes mass (using percentage testes mass as the dependent variable) across a variety of vertebrate groups. In all amniote lineages examined, the allometric relationship between body mass and testes mass was relatively strong and negative. We show, for the first time, that reptiles, birds and terrestrial placental mammals followed the same allometric relationship and, contrary to previous expectations, this relationship is sigmoidal rather than linear. Within this data set, there was no significant difference between this general amniote relationship and any of the 13 orders of reptiles, birds and terrestrial placental mammals examined. As a result, we propose that a sigmoidal relationship should be considered the default assumption for the form of the body mass – testes mass relationship within the amniote lineage. However, we also identify significant differences within some additional mammal groups (marsupials, bats and cetaceans). In each of these cases, only some sub‐groupings differed significantly from the general amniote relationship. In contrast to the amniotes, the relationship is relatively weak and positive in teleost fish and frogs suggesting that a negative allometric relationship is not universal in vertebrates. We explore whether variation in the body mass – testes mass relationships can be linked to sperm competition or a variety of ecological characteristics, either for amniotes in particular or vertebrates in general.