Human total, basal and activity energy expenditures are independent of ambient environmental temperature.

Lower ambient temperature (Ta) requires greater energy expenditure to sustain body temperature. However, effects of Ta on human energetics may be buffered by environmental modification and behavioral compensation. We used the IAEA DLW database for adults in the USA (n = 3213) to determine the effect of Ta (-10 to +30°C) on TEE, basal (BEE) and activity energy expenditure (AEE) and physical activity level (PAL). There were no significant relationships (p > 0.05) between maximum, minimum and average Ta and TEE, BEE, AEE and PAL. After adjustment for fat-free mass, fat mass and age, statistically significant (p < 0.01) relationships between TEE, BEE and Ta emerged in females but the effect sizes were not biologically meaningful. Temperatures inside buildings are regulated at 18-25°C independent of latitude. Hence, adults in the US modify their environments to keep TEE constant across a wide range of external ambient temperatures.

Assessment of maternal referral systems used for a rural Zambian hospital: the development of setting specific protocols for the identification of complications.

BACKGROUND: In resource-limited countries, it is estimated that up to 75% of maternal deaths are preventable. Maternal referral systems are an effective measure to help prevent these deaths. OBJECTIVE: The objective of this study was to delineate criteria that health care workers use to identify obstetrical emergencies and make referrals, in order to evaluate the effectiveness of the established referral system and to implement improvements to this system. METHODS: Using a qualitative study design, the individuals with the highest level of formal obstetrics training at 10 health posts that refer to a rural Zambian hospital were surveyed using semi-structured interviews regarding their referral protocols. Data were analyzed through open-coding. At the conclusion of the interview, standardized referral protocols for obstetric emergencies derived from published guidelines and local practices were distributed. RESULTS: Identified complications resulting in referral most commonly included post-partum hemorrhage (70%), prolonged labor (70%), malpresentation (50%), antepartum hemorrhage (40%), and retained placenta (40%). While numerous reasons for referral were identified, there was little consensus on the referral protocol used for each complication. Obstacles to successful referral most commonly included cellular network disruptions (70%), distance (50%), and lack of transportation (30%).The referral protocols distributed to health posts covered only 11 of the 23 complications cited as the most common reason for referral. CONCLUSION: The referral criteria and protocols were updated to include all of the reported complications. We propose this document for others working in resource-limited settings attempting to establish or evaluate a maternal referral systems.

Physical activity and pre-diabetes-an unacknowledged mid-life crisis: findings from NHANES 2003-2006.

The prevalence of pre-diabetes (PD) among US adults has increased substantially over the past two decades. By current estimates, over 34% of US adults fall in the PD category, 84% of whom meet the American Diabetes Association's criteria for impaired fasting glucose (IFG). Low physical activity (PA) and/or sedentary behavior are key drivers of hyperglycemia. We examined the relationship between PD and objectively measured PA in NHANES 2003-2006 of 20,470 individuals, including 7,501 individuals between 20 and 65 yrs.We excluded all participants without IFG measures or adequate accelerometry data (final N = 1,317). Participants were identified as PD if FPG was 100-125 mg/dL (5.6-6.9 mmol/L). Moderate and vigorous PA in minutes/day individuals were summed to create the exposure variable "moderate-vigorous PA" (MVPA). The analysis sample included 884 normoglycemic persons and 433 with PD. There were significantly fewer PD subjects in the middle (30.3%) and highest (24.6%) tertiles of PA compared to the lowest tertile (35.5%). After adjusting for BMI, participants were 0.77 times as likely to be PD if they were in the highest tertile compared to the lowest PA tertile (p < 0.001). However, these results were no longer significant when age and BMI were held constant. Univariate analysis revealed that physical activity was associated with decreased fasting glucose of 0.5 mg/dL per minute of MVPA, but multivariate analysis adjusting for age and BMI was not significant. Overall, our data suggest a negative association between measures of PA and the prevalence of PD in middle-aged US adults independent of adiposity, but with significant confounding influence from measures of BMI and age.

Adiposity is not equal in a multi-race/ethnic adolescent population: NHANES 1999-2004.

BMI is the preferred measure of adiposity in adolescents. Recent evidence suggests that in adults the relationship between BMI and adiposity can vary by age and race/ethnicity. We investigated the relationship between BMI and percent body fat (%BF) in a large multi-ethnic, nationally representative sample of US adolescents (National Health and Nutrition Examination Survey, NHANES, 1999-2004). BMI was calculated; %BF was derived from dual-energy X-ray absorptiometry data and compared to BMI among adolescents from three groups: non-Hispanic white (NHW), non-Hispanic black (NHB), and Mexican-American (MA). Fractional polynomials were used to model a new equation to estimate %BF from a given BMI. MA boys weighed significantly less than either NHW or NHB boys, while only NHB girls weighed significantly more than the other girls. Among the boys there were no differences in mean BMI, whereas %BF differed significantly between all three groups. For the girls, both BMI and %BF differed significantly the groups with MA girls having the highest %BF. The significant correlates for modeling %BF from BMI included gender, age, race/ethnicity, weight, [formula in text]: the final model explained 79% of the variance in %BF. NHB adolescents had significantly lower %BF for BMI and MA had higher than NHW. Our results indicate that BMI may not be an equivalent measure of %BF in a multi-ethnic population of US adolescents.

Energy expenditure and adiposity in Nigerian and African-American women.

OBJECTIVE: Obesity is a prevalent condition in industrialized societies and is increasing around the world. We sought to assess the relative importance of resting energy expenditure (REE) and activity EE (AEE) in two populations with different rates of obesity. METHODS AND PROCEDURES: Women of African descent between 18 and 59 years of age were recruited from rural Nigeria and from metropolitan Chicago. Total EE (TEE) was measured using the doubly labeled water (DLW) technique and REE by indirect calorimetry; AEE was calculated as the difference between TEE and the sum of REE plus a factor for the thermic effect of food. In the analyses all EE parameters were adjusted for body size using a regression method. Comparisons were made between the groups and associations between EE and adiposity examined. RESULTS: A total of 149 Nigerian and 172 African-American women completed the protocol. All body size measurements were lower in the Nigerian women. Adjusted TEE and REE were higher in the Nigerian cohort but adjusted AEE did not differ significantly. Adjustment for parity, seasonality, and recent illness did not modify mean AEE or adiposity. In neither cohort was there a meaningful association between measures of AEE and adiposity. DISCUSSION: In these cohorts of women from very different environments, AEE did not differ significantly nor was it associated cross-sectionally with adiposity. If generalizable, these findings suggest that reduction in AEE may have less of a role in the development of obesity than anticipated. The possibility remains that variation in type and duration of activity plays a role not captured by total AEE.

Heritability of blood pressure in Nigerian families.

OBJECTIVES: There are few studies of familial aggregation of blood pressure in African populations. This study was undertaken to provide estimates of heritability for four blood pressure phenotypes: systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and pulse pressure. METHODS: A population-based sample of 528 pedigrees or extended families, comprising 1825 measured individuals, was studied in a poor urban community in Ibadan, Nigeria. RESULTS: The mean SBP was 121.7 (SD 22.6) mmHg for men and 120.7 (SD 26.8) mmHg for women, while the mean DBP was 74.6 (SD 14.1) mmHg for men and 75.5 (SD 15.2) mm Hg for women. The study sample was lean [mean body mass index (BMI) approximately 21 kg/m2]. Maximum-likelihood heritability estimates were obtained under a polygenic model with simultaneous estimation of household effects using a variance components method, as implemented in the SOLAR software package. Heritability estimates of the traits were 34% for SBP, 29% for DBP, 36% for MAP and 13% for pulse pressure. Household effects were statistically significant for DBP (7.1%) and MAP (4.5%). Measured covariates (age, sex and BMI) accounted for 25, 24, 26 and 16% of the total variance, respectively, for SBP, DBP, MAP and pulse pressure. CONCLUSIONS: These figures suggest that, similar to that reported in other populations, blood pressure is a heritable trait. Studies similar to this are needed to describe the familial aggregation of other complex traits in sub-Saharan African populations and to serve as a prelude to the identification of susceptibility genes involved in the pathophysiology of common complex diseases, including blood pressure and hypertension.

Leptin and body composition of Nigerians, Jamaicans, and US blacks

The role of leptin in humans remains controversial. Leptin concentrations are highly correlated with body fat stores. We tested whether or not this relation was consistent across the range of body composition encompassing the lean as well as the obese. Individuals participating in community-based comparative research in Nigeria (n = 363), Jamaica (n = 372), and the United States (Maywood, IL; n = 699) had their plasma leptin concentrations and body compositions (with bioelectrical impedance analysis) measured. All participants identified themselves as being black. Body mass index (in KG/m2) ranged from across populations for both men and women in Nigeria, Jamaica, and the United States, respectively (men: 2.8, 3.9, and 6.8 microg/L; women: 10.3, 18.6, and 27.7 microg/L). An exponential function fit the relation between percentage body fat or total fat mass and leptin for men and women at each site. For women and men the exponential function with either percentage body fat or total fat mass was of the same shape, but increased by a constant in women, yielding higher leptin concentrations than in men at every level of body fat. On the basis of this broad distribution of body composition, the data suggest an exponential response of leptin to increase in body fat stores, consistent with the development of leptin resistance in individuals developing obesity. These findings likewise confirm that men and women exhibit different set points in terms of leptin production(AU)

Leptin concentration in women is influenced by regional distribution of adipose tissue

Leptin concentration in humans are increase with obesity, and women have higher leptin concentration than men. This sex difference reflects the greater fat mass of women. However, there is evidence that factors other than the size of the adipose tissue mass contribute to serum leptin concentrations. This study was undertaken to determine whether anthropometric factors influenced leptin concentrations in our population. Leptin concentrations were measured in 375 persons from a population study of hypertension and diabetes for whom body-composition data (bioelectrical impedance analysis and anthropometry) were available. Serum leptin concentrations were more than four times higher in women than in men (18.5 ñ 13.9 compared with 3.8 ñ 3.5 ng/L, P < 0.0001). In individuals with comparable body mass indexes, these differences persisted after adjustment for either percentage fat (P < 0.05) or fat mas (P < 0.0001) by multivariate-regression analysis. After fat mass was adjusted for, the serum leptin concentration in both men and women was independent of waist circumference but in women was associated with hip circumference. Hip circumference is a proxy measure of peripheral fat and these results suggest that the larger hips of women may contribute to the sex difference in serum leptin concentration.(AU)

Relation between body mass index and body fat in black population samples from Nigeria, Jamaica, and the United States

Body mass index (BMI) is the most commonly used measure of obesity. Recently, some investigators have advocated direct measurement of adiposity rather than use of the BMI. This study was undertaken to determine the ability of BMI to predict body fat levels in three populations of West Africa heritage living in different environments. A total of 1,054 black men and women were examined in Nigeria, Jamaica, and the United States during 1994 and 1995. A standardized protocol was used to measure height, weight, waist and hip circumferences, and blood pressure at all sites; percentage of body fat was estimated using bioelectrical impedance analysis. Percentage of body fat and BMI were highly correlated within site- and sex-specific groups, and the resulting r2 ranged from 0.61 to 0.85. The relation was quadratic in all groups except Nigerian men, in whom it was linear. The regression coefficients were similar across sites, yet the mean body fat levels differed significantly (p < 0.001) as estimated by the intercept, making intersite comparison difficult. Compared with BMI, percentage of body fat was not a better predictor of blood pressure or waist or hip circumference.(AU)

Relationship between blood pressure and body mass index in lean populations

Associations between body mass index (BMI) and blood pressure (BP) have been consistently observed, but remain poorly understood. One unresolved question is whether there is a linear relationship across the entire BMI range. We investigated this question among 11235 adult men and women from seven low-BMI populations in Africa and the Caribbean. We used kernel smoothing and multivariate linear and spline regression modeling to examine gender differences in the relationship and to test for a threshold. Age-adjusted slopes of BP on BMI were uniformly higher in men than women, with pooled slopes ratios of 2.00 and 2.20 for systolic and diastolic BPs, respectively. Men displayed no evidence of age modification or nonlinearity in the relationship, and the age-adjusted slope of systolic BP on BMI was 0.90 (95 percent confidence interval [CI], 0.76 to 1.04). Women demonstrated both age modification and nonlinearity. For both younger (<45 years) and older (45+ years) women, the optimal change point for a single threshold model was found to be 21kg/m. Slopes of systolic BP on BMI above this threshold were positive and significant: 0.68 (95 percent CI, 0.54 to 0.81) and 0.53 (95 percent CI, 0.29 to 0.76) for younger and older women, respectively. Slopes below the threshold were essentially zero for both groups of women, and difference between the slopes above and below the threshold was significant for younger women (P=.018). In summary, we observed a threshold at 21kg/m in the relationship between BMI and BP for women but not for men. This contributes to the effort to identify the mechanism that underlie this relationship and how they differ by gender.(AU)