Akilah Dulin-Keita

Differential Influence of Diet and Physical Activity on Components of Metabolic Syndrome in a Multiethnic Sample of Children

BACKGROUND Treatment of the metabolic syndrome in adults is generally approached with diet and physical activity. The influence of diet and physical activity on cardiometabolic outcomes in children has not been clearly established. OBJECTIVE The main objective of this study was to test the hypothesis that the distribution of energy from fat and carbohydrate in addition to limited time spent engaging in physical activity would contribute to the prevalence of the metabolic syndrome and its components in a multiethnic pediatric population. DESIGN Observational, cross-sectional study. Diet was assessed by two 24-hour recalls, physical activity by accelerometry, body composition by dual-energy absorptiometry, and glucose and lipid levels using fasting sera. MAIN OUTCOME MEASURES Presence of metabolic syndrome and its components. SUBJECTS 202 African-American (n=79), white (n=68), or Hispanic (n=55) healthy children aged 7 to 12 years. STATISTICAL ANALYSIS The contribution of diet and physical activity to the metabolic syndrome and its components were assessed by logistic regression and multiple linear regression analyses. RESULTS Prevalence of the metabolic syndrome in the total sample was 8.4%, with Hispanics more likely than whites and African Americans to meet the criteria. A greater intake of energy from carbohydrate was related to a greater waist circumference and higher concentrations of triglyceride and glucose particularly apparent within the African-American sample (P<0.05). Fat intake was associated with a lower waist circumference (P<0.05) and with lower concentrations of triglyceride (P<0.05) and glucose (P<0.001) in the total sample. Greater moderate/hard physical activity was associated with higher high-density lipoprotein cholesterol concentrations in whites (P<0.05). Increased sedentary behavior was related to greater glucose concentration in whites and Hispanics (P<0.05 for both). CONCLUSIONS Diet composition was more closely related to the components of the metabolic syndrome than was physical activity, with carbohydrate intake being adversely related to waist circumference, triglyceride levels, and glucose levels. Furthermore, relationships among diet and metabolic syndrome outcomes were stronger among African-American children, suggesting that nutrition interventions in this group may be particularly beneficial.

Parental feeding practices and socioeconomic status are associated with child adiposity in a multi-ethnic sample of children

Parental feeding practices have been associated with childrens weight status, but results have been inconsistent across populations. Research is needed to elucidate the relationship between parental feeding practices and adiposity in diverse populations. The present study tested if: (1) parental feeding practices differed by race/ethnicity, (2) parental pressure to eat and parental restriction were associated with adiposity levels, and (3) to investigate the relationship between parental feeding practices and/or child adiposity with socioeconomic status (SES). Structural equations modeling was conducted to test the model in 267 children aged 7-12 years self-identified as African American (AA), European American (EA), or Hispanic American (HA) from economically diverse backgrounds. Dual energy X-ray absorptiometry and computed tomography scanning were used to determine body composition and abdominal fat distribution, respectively. Parental restriction was a significant predictor of child adiposity while parental pressure to eat had an inverse relationship with child adiposity. HA parents reported significantly higher levels of restriction and pressure to eat, whereas EA parents reported the lowest. SES was positively associated with child adiposity and inversely related to parental restriction and pressure to eat. Thus, parental feeding practices differ across racial/ethnic groups and SES and may contribute to population differences in child adiposity.

Do neighbourhoods matter? Neighbourhood disorder and long-term trends in serum cortisol levels

Background Characteristics associated with low socioeconomic status neighbourhoods may put children at risk for unique chronic stressors that affect cortisol levels. This research sought to explore whether neighbourhood stressor exposure affected serum cortisol levels among children. Methods A total of 148 African and European-American children with an average age of 8.28 years participated in a longitudinal study evaluating ethnic differences in body composition and disease risk. Five waves of data were included in analyses. Mixed modelling was used to explore neighbourhood stressors, which was a composite index of five items for zip code level poverty and physical disorder, and serum cortisol outcomes for the full sample, by race/ethnicity and gender. Adjustments were made for individual level correlates age, pubertal status, gender and total fat mass. Results Neighborhood disorder was predictive of lower serum cortisol levels among African-American children (p<0.05), such that higher neighbourhood stressor exposure resulted in lower serum cortisol over time compared with individuals in socially ordered neighbourhoods. Neighbourhood disorder was marginally significant and predictive of higher serum cortisol among European-American children (p<0.10). Transition to a higher pubertal status, nested in age was also predictive of lower serum cortisol levels (p<0.01) among European-American children. Conclusion Children who are exposed to negative socioenvironmental climates over time are more likely to have altered serum cortisol levels. This may be an adaptive mechanism to cope with stress; however, disrupted cortisol levels may have negative effects on general physical and mental health.

Genetic influences in childhood obesity: recent progress and recommendations for experimental designs

The increasing prevalence of pediatric obesity around the world has become an area of scientific interest because of public health concern. Although since early stages of the lifespan body weight might be heavily influenced by an individuals behavior, epidemiological research highlights the involvement of genetic influences contributing to variation in fat accumulation and thus body composition. Results from genome-wide association studies and candidate gene approaches have identified specific regions across the human genome influencing obesity-related phenotypes. Reviewing the scientific literature provides support to the belief that at the conceptual level scientists understand that genes and environments do not act independently, but rather synergistically, and that such interaction might be the responsible factor for differences within and among populations. However, there is still limited understanding of genetic and environmental factors influencing fat accumulation and deposition among different populations, which highlights the need for innovative experimental designs, improved body composition measures and appropriate statistical methodology.

The associations of perceived neighborhood disorder and physical activity with obesity among African American adolescents

BackgroundAccording to recent research studies, the built and socioeconomic contexts of neighborhoods are associated with African American adolescents’ participation in physical activity and obesity status. However, few research efforts have been devoted to understand how African American adolescents’ perceptions of their neighborhood environments may affect physical activity behaviors and obesity status. The objective of the current study was to use a perceived neighborhood disorder conceptual framework to examine whether physical activity mediated the relationship between perceived neighborhood disorder and obesity status among African American adolescents.MethodsThe data were obtained from a cross-sectional study that examined social and cultural barriers and facilitators of physical activity among African American adolescents. The study included a sample of 101 African American adolescents age 12 to 16 years and their parents who were recruited from the Birmingham, Alabama metropolitan area. The primary outcome measure was obesity status which was classified using the International Obesity Task Force cut off points. Moderate-to-vigorous physical activity was assessed via accelerometry. Perceived neighborhood disorder was assessed using the Perceived Neighborhood Disorder Scale. Mediation models were used to examine whether the relationship between neighborhood disorder and obesity status was mediated by physical activity.ResultsPerceived neighborhood disorder was significantly and positively related to obesity status and moderate-to-vigorous physical activity was inversely associated with obesity status. However, there was no evidence to support a significant mediating effect of moderate-to-vigorous physical activity on the relationship between neighborhood disorder and obesity status.ConclusionFuture studies should longitudinally assess perceived neighborhood disorder characteristics and childhood adiposity to examine the timing, extent, and the mechanisms by which perceived neighborhood disorder characteristics increase the risk of obesity.

Genetic admixture, social–behavioural factors and body composition are associated with blood pressure differently by racial–ethnic group among children

Cardiovascular disease has a progressively earlier age of onset, and disproportionately affects African Americans (AAs) in the United States. It has been difficult to establish the extent to which group differences are due to physiological, genetic, social or behavioural factors. In this study, we examined the association between blood pressure and these factors among a sample of 294 children, identified as AA, European American or Hispanic American. We use body composition, behavioural (diet and physical activity) and survey-based measures (socio-economic status and perceived racial discrimination), as well as genetic admixture based on 142 ancestry informative markers (AIMs) to examine associations with systolic and diastolic blood pressure. We find that associations differ by ethnic/racial group. Notably, among AAs, physical activity and perceived racial discrimination, but not African genetic admixture, are associated with blood pressure, while the association between blood pressure and body fat is nearly absent. We find an association between blood pressure and an AIM near a marker identified by a recent genome-wide association study. Our findings shed light on the differences in risk factors for elevated blood pressure among ethnic/racial groups, and the importance of including social and behavioural measures to grasp the full genetic/environmental aetiology of disparities in blood pressure.

The defining moment: children's conceptualization of race and experiences with racial discrimination

Abstract This paper examines whether children of marginalized racial/ethnic groups have an awareness of race at earlier ages than youth from non-marginalized groups, documents their experiences with racial discrimination and utilizes a modified racism-related stress model to explore the relationship between perceived racial discrimination and self-esteem. Data were collected for non-Hispanic black, non-Hispanic white and Hispanic children aged 7–12 using face-to-face interviews (n=175). The concept of race was measured by assessing whether children could define race, if not a standard definition was provided. Racial discrimination was measured using the Williams Every-day-Discrimination Scale, self-esteem was measured using the Rosenberg Scale and ethnic identity was assessed using the Multi-group Ethnic Identity Measure. Non-Hispanic black children were able to define race more accurately, but overall Hispanic children encountered more racial discrimination, with frequent reports of ethnic slurs. Additionally, after accounting for ethnic identity, perceived racial discrimination remained a salient stressor that contributed to low self-esteem.

Intrabdominal fat is related to metabolic risk factors in Hispanic Americans, African Americans, and in girls

Aim:  This study aimed to test the association of individual adipose depots on cardiometabolic outcomes, whether the association varied by depot and if the associations differed by race/ethnicity or gender in early pubertal children.

Adjusting Adiposity and Body Weight Measurements for Height Alters the Relationship With Blood Pressure in Children

BACKGROUND Adiposity measures are associated with increased pediatric blood pressure (BP). However, this correlation can be confounded by the relationship of both variables to height. We evaluated whether adiposity and anthropometric measures were associated with pediatric BP before and after adjusting each value for height. METHODS Participants included 281 African-American (AA), European-American (EA), and Hispanic-American (HA) children aged 7-12 years. BP percentiles were calculated according to pediatric guidelines using the average of four measurements. Total fat mass was determined using dual-energy X-ray absorptiometry. Socioeconomic status (SES) was calculated with the Hollingshead index. Adiposity measures were indexed for height using log-log regression analysis. Partial correlations identified measures associated with BP. Linear regression was used to test the association of those measures with absolute BP, whereas logistic regression was used to evaluate the odds for hypertension. RESULTS More AAs (16.3%) presented with potential hypertension than EA (5.1%) or HA (2.7%) children. After adjusting for covariates, fat mass, body mass index, and waist circumference were positively significantly associated with absolute BP and hypertension in AA and EA children (P < 0.05). When these measures were height-indexed, only waist remained significantly positively associated with hypertension risk in these two groups. No measures were significantly associated with BP among HA children. CONCLUSIONS In this multiethnic pediatric population, waist circumference was the strongest significant adiposity predictor of hypertension risk among AA and EA children. Additional research is needed to determine which environmental and genetic factors contribute to pediatric hypertension, particularly among HA groups.

Reduced carbohydrate diet to improve metabolic outcomes and decrease adiposity in obese peripubertal African American girls.

Objective: Obesity prevalence among African American (AA) girls is higher than that in other groups. Because typical energy-restriction obesity treatment strategies have had limited success, alterations in macronutrient composition may effectively improve metabolic outcomes in this population and affect future body composition trajectories. The objective was to evaluate the efficacy of a moderately restricted carbohydrate (CHO) versus a standard CHO diet on weight/fat loss and metabolic parameters in overweight/obese AA girls ages 9 to 14 years. Methods: A total of 26 AA girls (ranging from 92nd body mass index percentile and above) were assigned to either a reduced- (SPEC: 42% energy from CHO, n = 12) or a standard- (STAN: 55% of energy from CHO, n = 14) CHO diet (protein held constant) for 16 weeks. All of the meals were provided and clinically tailored to meet the estimated energy requirements (resting energy expenditure × 1.2 in eucaloric phase and resting energy expenditure × 1.2 − 1000 kcal in energy deficit phase). The first 5 weeks encompassed a eucaloric phase evaluating metabolic changes in the absence of weight change. The subsequent 11 weeks were hypocaloric (1000 kcal/day deficit) to promote weight/fat loss. Meal tests were performed during the eucaloric phase for metabolic analyses. Dual-energy x-ray absorptiometry was used to evaluate body composition. Results: Both groups experienced reductions in weight/adiposity, but the difference did not reach significance. The solid meal test indicated improved glucose/insulin homeostasis on the SPEC diet up to 3 hours postingestion. In addition, significantly lower triglycerides (P < 0.001) were observed on the SPEC diet. Conclusions: Dietary CHO reduction favorably influences metabolic parameters but did not result in greater weight/fat loss relative to a standard diet in obese AA girls. Future research is needed to determine long-term effectiveness of a reduced CHO diet on glucose and insulin homeostasis and how it may apply to weight maintenance/fat loss during development alone and/or in combination with additional weight loss/metabolic improvement strategies.