Most health promotion programs that have produced significant changes in physical activity (PA) in children and adults were developed based on cognitive-behavioral theories, which hypothesize that behavioral change is the result of the change in mediating psychosocial and environmental factors. However, very few studies have tested the mediator-behavior relation based on these theories. PURPOSE: This study used the theory of reasoned action (TRA) and social cognitive theory (SCT) to explore the relationships between psycho-social factors, and PA and health outcomes. METHODS: Subjects were 141 African-American females (mean+-SD, age: 9.5+ −0.90; BMI: 20.7+ −5.26) participating in an exercise intervation project; the data for this report were collected prior to the intervention. Psycho-social factors were assessed by questionnaires and included beliefs of PA outcomes, social influence, self-efficacy (SE), intention to be physically active (Intention). Behavioral and health outcomes included 7-day recall of moderate PA (MPA), cardiovascular fitness (multi-stage treadmill test), sexual maturation, and percent fat and bone mineral density (BMD) measured with dual-energy x-ray absorptiometry. RESULTS: Path analysis using structural equation models was applied to test the fit of data to the hypothesized relationships between psycho-social variables, and PA and health outcomes. Overall, after adjusting for sexual maturation and age, the data demonstrated a good fit to the TRA-based model (chi-square (23) = 16.89, p = .81, GFI= 1.00, RMSEA= .0001) and the SCT-based model (chi-square (22)= 20.25, p = .57, GFI= 1.00, RMSEA= .0001). Decomposition of effects indicated significant relationships of some of the components in TRA and SCT with MPA and health outcomes (fitness and BMD). CONCLUSION: Partial support was provided for a linkage between psycho-social factors (Intention and SE) and PA and health outcomes as hypothesized by TRA and SCT. Prospective studies should be conducted to test the suggested relationship using a large study sample. Supported by a grant from NIH (HL64972)
Background: Dietary fat and Vitamin D each influence adipose tissue and bone development; the present study investigated possible interactions between these factors in weanling rats.Methods: Female Sprague-Dawley rats (n=32) were divided into an HF group that consumed a high-fat (60% fat, 20% carb) diet and an LF group that consumed a low-fat (15% fat, 65% carb) diet ad libitum.Half the rats in each group received the AIN requirement for Vitamin D (+) whereas the other half received added calcium (to prevent hypocalcemia) but no Vitamin D (-).Results: After 6 wks, the four groups exhibited similar energy intakes, body weights, and % body fat.However, periovarian fat cell size and hepatic lipid content of HF-rats exceeded that of HF+ or LF rats (p<0.005).Hepatic lipid levels from individual rats paralleled concomitant values of periovarian fat cell size (p<0.05)and % body fat (p<0.05).Examination of the trabecular region of the right femur revealed that the structural model index (SMI) was lower in HF than LF rats (p<0.05),indicating a more plate-like vs. rod-like architecture.Percent bone volume, trabecular number, and trabecular thickness were all greater in HF than LF rats (p<0.05),regardless of Vitamin D intake (HF+~HF-and LF+~LF-).Conclusions: The present findings show that: 1) Vitamin D mitigated the increase in hepatic lipid and fat cell size produced by the HF diet; and 2) in contrast to young male rats, the HF diet produced a greater quantity of trabecular bone in female rats.
Context-Pediatric studies showed that aerobic exercise reduces metabolic risk, but dose response information is not available. Objective-Test the effect of aerobic training dose on insulin resistance, fatness, visceral fat, and fitness in overweight, sedentary children, and test moderation by sex and race.Design, Setting, and Participants-Randomized, controlled, efficacy trial from 2003 through 2007, in which 222 overweight or obese, sedentary children (mean age, 9.4 yrs; 42% male, 58% black) were recruited from 15 public schools in the Augusta, GA area.Intervention-Low-dose (20 min/d, n = 71) or high-dose (40 min/d, n = 73) aerobic training (13 ± 1.6 wk, 5 d/wk), or control condition (usual physical activity, n = 78); 94% retention.Main outcome measures-Prespecified primary outcomes were type 2 diabetes risk at posttest, assessed by insulin area under the curve (AUC) from oral glucose tolerance test, aerobic fitness, percent body fat via dual-energy x-ray absorptiometry, and visceral fat via magnetic resonance, analyzed by intent-to-treat.Results-Most children (85%) were obese.At baseline, the mean BMI was 26 (SD = 4.4).Reductions in insulin AUC were larger in the high-dose (adjusted mean difference [95% CI], -3.56 [-6.26 to -0.85], P = .01)than low-dose group (-2.96 [-5.69 to -0.22], P = .03)×10 3 μU/ mL) vs control group.Dose-response trends were also observed for body fat (-1.4 [-2.2 to -0.7], P < .001;-0.8 [-1.6 to -0.07] %, P =.03) and visceral fat (-3.9 [-6.0 to -1.7], P < .001;-2.8 [-4.9 to -0.6] cm 3 , P = .01)in the high-and low-dose vs control groups, respectively.Effects in the high-and low-dose groups vs control were similar for fitness (2.4 [0.4 to 4.5], P =.02; 2.4 [0.3 to 4.5] mL/kg/min, P = .03).High-vs.low-dose group effects were similar for these outcomes.
Liver in Overweight Black Children Miriam Vos, MD, MSPH1, Norman Pollock, PhD2, Rachel Elam, ScM2, Jerry Allison, PhD3, Haidong Zhu, MD PhD2, James Rawson MD3, Reda Bassali, MD2, Priya Patel MS2, Stephen Elmore MD2, Catherine Davis, PhD2 1Department of Pediatrics, Gastroenterology, Hepatology and Nutrition, Emory University School of Medicine, Atlanta, GA, USA 2Georgia Prevention Center, Department of Pediatrics, Medical College of Georgia, Institute of Public and Preventive Health, Georgia Regents University, Augusta, GA, USA 3Department of Radiology, Medical College of Georgia, Georgia Regents University, Augusta, GA, USA
Increased waist circumference has been shown to contribute to cardiovascular risk in obese adults. This study was designed to examine whether routinely assessing waist circumference in obese children adds predictive value for the development of diabetes and other cardiovascular risk factors.This is a cross-sectional study on a community sample of 188 apparently healthy obese children 7-11 years, 60% black, 39% male. Anthropometry, fasting lipid profile, oral glucose tolerance test, and magnetic resonance imaging of abdominal fat were done. High waist circumference was defined as > or = 90(th) percentile for age and sex. Statistical analyses were done to examine the relationship between waist circumference and the different cardiovascular risk factors.Those with a high waist circumference had significantly lower high-density lipoprotein, higher triglycerides, fasting insulin, insulin response to glucose, subcutaneous and visceral abdominal fat than those with a normal waist circumference. Children with a high waist circumference were 3.6 times more likely than those with a normal waist status to have a low high-density lipoprotein level, 3.0 times more likely to have high triglycerides, and 3.7 times more likely to have a high fasting insulin level.Obese children with waist circumference at or above the 90th percentile are at higher risk for dyslipidemia and insulin resistance than obese children with normal waist circumference. These results indicate that routine waist circumference evaluation in obese children may help clinicians identify which obese children are at greater risk of diabetes and other cardiovascular disease.
