Exercise effects on arterial stiffness and heart health in children with excess weight: The SMART RCT.

INTRODUCTION: Childhood obesity and inactivity are associated with cardiovascular risk. Evidence is limited for exercise effects on arterial health in children. METHODS: One hundred and seventy-five inactive children with overweight or obesity (8-11 years, ≥85th percentile BMI, 61% female, 87% Black, 73% with obesity) were randomized to an 8-month daily after-school aerobic exercise program (40 min/day, n = 90) or a sedentary control condition (n = 85). Carotid-femoral pulse wave velocity (PWV, primary outcome, arterial stiffness), fitness, adiposity, blood pressure (BP), glucose, insulin resistance, lipids, and C-reactive protein were measured at baseline and posttest (8 months). Adiposity, fitness, and BP were measured again at follow-up, 8-12 months later. Intent-to-treat analyses were conducted using mixed models. RESULTS: The study had 89% retention, with attendance of 59% in exercise and 64% in the control condition, and vigorous exercise participation (average heart rate 161 ± 7 beats/min). Compared with controls, the exercise group had twice the improvement in fitness (VÈ®2 peak, 2.7 (95% CI 1.8, 3.6) vs. 1.3 (0.4, 2.3) mL/kg/min) and adiposity (-1.8 (-2.4, -1.1) vs. -0.8 (-1.5, -0.1)%), each p = 0.04, and a large improvement in HDL-cholesterol (0.13 (0.075, 0.186) vs. -0.028 (-0.083, 0.023) mmol/L, p < 0.0001). There was no group × time effect on other outcomes at 8 months, or on any outcomes at follow-up. The change in PWV at 8 months correlated with changes in insulin and insulin resistance (both r = 0.32), diastolic BP (r = 0.24), BMI (r = 0.22), and adiposity (r = 0.18). CONCLUSIONS: Eight months of aerobic exercise training improved fitness, adiposity, and HDL-cholesterol levels, but did not reduce arterial stiffness in children with excess weight. PWV improved as a function of insulin resistance, BP, BMI, and adiposity. Weight loss may be required to improve arterial stiffness. Exercise benefits waned after discontinuing the program.

Exercise dose and diabetes risk in overweight and obese children: a randomized controlled trial.

CONTEXT: Pediatric studies have shown that aerobic exercise reduces metabolic risk, but dose-response information is not available. OBJECTIVES: To test the effect of different doses of aerobic training on insulin resistance, fatness, visceral fat, and fitness in overweight, sedentary children and to test moderation by sex and race. DESIGN, SETTING, AND PARTICIPANTS: Randomized controlled efficacy trial conducted from 2003 through 2007 in which 222 overweight or obese sedentary children (mean age, 9.4 years; 42% male; 58% black) were recruited from 15 public schools in the Augusta, Georgia, area. INTERVENTION: Children were randomly assigned to low-dose (20 min/d; n = 71) or high-dose (40 min/d; n = 73) aerobic training (5 d/wk; mean duration, 13 [SD, 1.6] weeks) or a control condition (usual physical activity; n = 78). MAIN OUTCOME MEASURES: The prespecified primary outcomes were postintervention type 2 diabetes risk assessed by insulin area under the curve (AUC) from an oral glucose tolerance test, aerobic fitness (peak oxygen consumption [VO2]), percent body fat via dual-energy x-ray absorptiometry, and visceral fat via magnetic resonance, analyzed by intention to treat. RESULTS: The study had 94% retention (n = 209). Most children (85%) were obese. At baseline, mean body mass index was 26 (SD, 4.4). Reductions in insulin AUC were larger in the high-dose group (adjusted mean difference, -3.56 [95% CI, -6.26 to -0.85] × 10(3) µU/mL; P = .01) and the low-dose group (adjusted mean difference, -2.96 [95% CI, -5.69 to -0.22] × 10(3) µU/mL; P = .03) than the control group. Dose-response trends were also observed for body fat (adjusted mean difference, -1.4% [95% CI, -2.2% to -0.7%]; P < .001 and -0.8% [95% CI, -1.6% to -0.07%]; P = .03) and visceral fat (adjusted mean difference, -3.9 cm3 [95% CI, -6.0 to -1.7 cm3]; P < .001 and -2.8 cm3 [95% CI, -4.9 to -0.6 cm3]; 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 (adjusted mean difference in peak VO2, 2.4 [95% CI, 0.4-4.5] mL/kg/min; P = .02 and 2.4 [95% CI, 0.3-4.5] mL/kg/min; P = .03, respectively). High- vs low-dose group effects were similar for these outcomes. There was no moderation by sex or race. CONCLUSION: In this trial, after 13 weeks, 20 or 40 min/d of aerobic training improved fitness and demonstrated dose-response benefits for insulin resistance and general and visceral adiposity in sedentary overweight or obese children, regardless of sex or race. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00108901.

Prevalence of cardiovascular risk factors in schoolchildren in a rural Georgia community.

BACKGROUND: In the context of a national childhood obesity epidemic, this study sought to document the cardiovascular risk status of children in a rural Georgia community. METHODS: Anthropometrics and blood pressure were measured in 211 children, and fasting glucose and lipid profile in 160, recruited from schools in 2002 (grades 2 to 11, ages 7 to 18 years). RESULTS: Nearly half the schoolchildren (48%) were overweight or at risk of overweight; 15% had metabolic syndrome. Overweight children were at higher risk for metabolic syndrome and had more risk factors. Blood pressure: 19% had elevated systolic blood pressure; 4% had elevated diastolic blood pressure. Glycemia: 14% had impaired fasting glucose levels; no diabetes cases were detected. Lipid profile: 26% had high total cholesterol (>170 mg/dL), 20% had high low-density lipoprotein (>110 mg/dL), 13% had high triglycerides (>150 mg/dL), 43% had low high-density lipoprotein (females, <50 mg/dL; males, <40 mg/dL). Ethnicity, gender, and grade level were not predictive of risk except that fewer black children had low high-density lipoprotein, and blood pressure and body mass index increased with grade, as expected. CONCLUSIONS: Results from this study indicate a significant problem with overweight and cardiovascular risk in rural schoolchildren. Notably, younger children were just as likely to have risk factors as adolescents, suggesting that screening and intervention ought to begin by school age. Ethnic and gender differences in prevalence were not found, suggesting that contextual factors in a rural setting may outweigh demographic influences on risk.

Lower uncarboxylated osteocalcin concentrations in children with prediabetes is associated with beta-cell function.

CONTEXT: Although animal studies suggest that it is the uncarboxylated rather than carboxylated form of osteocalcin that affects glucose homeostasis, the human data are scant and equivocal. OBJECTIVE: This study investigated associations of uncarboxylated and carboxylated forms of osteocalcin with insulin sensitivity and ß-cell function in 140 overweight prepubertal children (43% female, 46% black, 84% obese) with normal glucose levels (n = 99) and prediabetes (n = 41). METHODS: An oral glucose tolerance test was used to identify prediabetes and for measurement of insulin sensitivity (Matsuda index), ß-cell function [oral glucose tolerance test derived insulinogenic index and disposition index (DI(OGTT))] and uncarboxylated and carboxylated forms of osteocalcin. Visceral adipose tissue (VAT) was assessed using magnetic resonance imaging. RESULTS: After controlling for age, sex and race, lower uncarboxylated osteocalcin concentrations, Matsuda index, insulinogenic index, and DI(OGTT) and higher VAT levels were found in the prediabetes vs. normal-glucose group (all P < 0.03). Carboxylated osteocalcin levels were not different between groups. Multiple linear regression adjusting for age, sex, race, and VAT revealed that uncarboxylated osteocalcin was associated with insulinogenic index and DI(OGTT) (ß = 0.34, 0.36, respectively, both P < 0.04) in the prediabetes group but not the normal-glucose group. In both the normal-glucose and prediabetes groups, carboxylated osteocalcin was associated with insulin sensitivity (ß = 0.26, 0.47, respectively, both P < 0.02). CONCLUSIONS: These data suggest that the lower uncarboxylated osteocalcin concentrations found in children with prediabetes may be associated with ß-cell dysfunction. In addition, our findings between carboxylated osteocalcin and insulin sensitivity suggest that carboxylated osteocalcin plays a role in human glucose homeostasis.

Utility of waist circumference percentile for risk evaluation in obese children.

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

A 16-week randomized clinical trial of 2000 international units daily vitamin D3 supplementation in black youth: 25-hydroxyvitamin D, adiposity, and arterial stiffness.

CONTEXT: Vitamin D insufficiency/deficiency is commonly observed in black youth. OBJECTIVE: The aim was to determine 25-hydroxyvitamin D [25(OH)D] in response to 2000 IU vitamin D supplementation over time; to evaluate the relation between 25(OH)D concentrations and total body fat mass by dual-energy x-ray absorptiometry; and to determine whether vitamin D supplementation improves arterial stiffness measured by pulse wave velocity (PWV). DESIGN: We conducted a randomized, blinded, controlled clinical trial. SETTING AND PARTICIPANTS: Forty-nine normotensive black boys and girls, aged 16.3 ± 1.4 yr, were randomly assigned to either the control group (400 IU/d; n = 24) or the experimental group (2000 IU/d; n = 25). RESULTS: Plasma 25(OH)D values at baseline and at 4, 8, and 16 wk were 34.0 ± 10.6, 44.9 ± 9.4, 51.2 ± 11.1, and 59.8 ± 18.2 nmol/liter, respectively, for the control group; and 33.1 ± 8.7, 55.0 ± 11.8, 70.9 ± 22.0, and 85.7 ± 30.1 nmol/liter, respectively, for the experimental group. The experimental group vs. the control group reached significantly higher 25(OH)D concentrations at 8 and 16 wk, respectively. Partial correlation analyses indicated that total body fat mass at baseline was significantly and inversely associated with 25(OH)D concentrations in response to the 2000-IU supplement across time. Furthermore, carotid-femoral PWV increased from baseline (5.38 ± 0.53 m/sec) to posttest (5.71 ± 0.75 m/sec) in the control group (P = 0.016), whereas in the experimental group carotid-femoral PWV decreased from baseline (5.41 ± 0.73 m/sec) to posttest (5.33 ± 0.79 m/sec) (P = 0.031). CONCLUSION: Daily 2000 IU vitamin D supplementation may be effective in optimizing vitamin D status and counteracting the progression of aortic stiffness in black youth. Plasma 25(OH)D concentrations in response to the 2000 IU/d supplementation are negatively modulated by adiposity.

Relations of body fatness and cardiovascular fitness to lipid profile in black and white adolescents.

High body fatness is associated with unfavorable cardiovascular disease risk profiles in juveniles. However, the degree to which the deleterious effects attributed to fatness may actually be due to the low cardiovascular fitness (CVF) that is usually confounded with fatness is not known. This study determined in 14- to 18-y-old (n = 398) youths the degree to which percentage body fat (%BF) and CVF explained variability in lipids and lipoproteins. Blood samples were taken after a 12-h fast. %BF was measured with dual-energy x-ray absorptiometry. CVF was determined with a multistage treadmill test. The degree to which %BF and CVF explained variance in outcome variables was determined by regression analyses, controlling for demographic variables before entering %BF or CVF and their interactions with race and sex. Because %BF and CVF were highly correlated (r = -0.69, p < 0.001), they were first entered separately in the regression models before being considered together. Both higher %BF and lower CVF were associated with unfavorable concentrations of total cholesterol to HDLC ratio and triglycerides. However, the effects of %BF and CVF were not additive; once %BF was in the regression model, CVF did not explain additional variance. For Lp(a), only %BF explained a significant portion of the variance. For triglycerides, there was a %BF by race interaction, such that the deleterious effects of high %BF were greater in whites than in blacks. These results suggest that interventions to improve lipid profile in youths should be designed primarily to minimize fatness.