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1.  Leptin predicts a decline in moderate to vigorous physical activity in minority female children at risk for obesity 
Pediatric obesity  2012;8(1):70-77.
Background
Leptin may influence moderate to vigorous physical activity (MVPA) at the start of puberty. The direction and magnitude of this association is unclear.
Objectives
To determine the effect of baseline leptin on MVPA over one year in minority girls at high-risk for obesity.
Methods
Data came from TRANSITIONS, a longitudinal observational study on the age-related MVPA decline. Fifty peri-pubertal girls aged 8–11 years at baseline participated. Baseline leptin (ng/mL) was collected via a duplicated assay using a double antibody Radio Immune Assay. MVPA (min/day) was measured using accelerometers for at least four 10-hr days on a quarterly basis for up to one year.
Results
Continuous leptin was negatively related to MVPA (p=0.001) independent of central adiposity at baseline and predicted the MVPA decline over one year (p=0.002). For descriptive purposes, baseline leptin was dichotomized at the sample median into ‘high leptin’ and ‘low leptin’ categories to determine whether MVPA trajectories differed between these groups. Girls with ‘low leptin’ at baseline had significantly higher levels of MPVA at baseline, visit 1, and visit 2 compared to girls with ‘high leptin’.
Conclusions
High leptin levels predicted nearly a 12.6% decline in MVPA over one year. These findings provide support for the biological basis of declining MVPA as girls enter puberty.
doi:10.1111/j.2047-6310.2012.00091.x
PMCID: PMC3527645  PMID: 22991241
leptin; accelerometer; biological basis; physical activity; adolescent
2.  Objective Habitual Physical Activity and Estradiol Levels in Obese Latina Adolescents 
Background
Lifetime physical activity (PA) is associated with decreased breast cancer (BC) risk; reports suggest that PA during adolescence contributes strongly to this relationship. PA lowers production of sex hormones, specifically estradiol, or decreases insulin resistance (IR), thereby lowering risk. Overweight Latina adolescents are insulin resistant and exhibit low levels of PA, potentially increasing their future BC risk.
Methods
37 obese Latina adolescents (15.7 ±1.1 yrs) provided measures of PA using accelerometry; plasma follicular phase estradiol, sex-hormone binding globulin, total and free testosterone, dehydroepiandrosterone-sulfate (DHEAS); IR using HOMA-IR; body composition via DEXA. Partial correlations and stepwise linear regressions assessed cross-sectional relationships between sex hormones, IR and PA. Body composition, and age were included a priori as covariates.
Results
Estradiol was negatively associated with accelerometer counts per minute (CPM) (r= −0.4; p=0.02), percent time spent in moderate PA (%MPA) (r= −0.5; p=0.006), and percent time in moderate or vigorous PA (%MVPA) (r= −0.5; p=0.007). DHEAS was positively associated with CPM (r=0.4, p=0.009), %MPA (r=0.3, p=0.04), and %MVPA (r=0.3, p=0.04). Other sex hormones and IR were not associated with PA measures.
Conclusion
This study is the first to show that higher habitual PA was inversely associated with estradiol in obese adolescents.
PMCID: PMC3779056  PMID: 23038707
Accelerometer; insulin resistance; sex hormones; breast cancer
3.  Increasing Physical Activity Decreases Hepatic Fat and Metabolic Risk Factors 
This study assessed the changes in time spent in moderate to vigorous physical activity (MVPA) on fat depots, insulin action, and inflammation. Longitudinal data were generated from 66 Hispanic adolescents (15.6±1.1 yr; BMI percentile 97.1±3.0) who participated in a 16-wk nutrition or nutrition+exercise intervention. There were no effects of the intervention on PA, but there were inter-individual changes in PA. For purposes of this analysis, all intervention groups were combined to assess how changes in PA during 16 wk affected changes in adiposity, insulin action, and markers of inflammation. MVPA was assessed by 7-day accelerometry, total body fat via DXA, liver fat by MRI, and insulin, glucose and HOMA-IR via a fasting blood draw. A repeated measures ANCOVA was used to assess the effect of MVPA on fat depots, insulin action, and inflammatory markers. Sixty-two percent of participants increased MVPA (mean increase, 19.7±16.5 min/day) and 38% decreased MVPA (mean decrease, 10.7±10.1 min/day). Those who increased MVPA by as little as 20 min per day over 16 wk, compared to those who decreased MVPA, had significant reductions in liver fat (−13% vs. +3%; P=0.01), leptin levels (−18% vs. +4%; P=0.02), and fasting insulin (−23% vs. +5%; P=0.05). These findings indicate that a modest increase in MVPA can improve metabolic health in sedentary overweight Hispanic adolescents.
PMCID: PMC3695481  PMID: 23814456
Moderate-to-Vigorous Physical Activity; Obesity
4.  Randomized Controlled Trial to Improve Adiposity, Inflammation, and Insulin Resistance in Obese African-American and Latino Youth 
Obesity (Silver Spring, Md.)  2011;20(4):811-818.
The purpose of this study was to examine ethnic differences in the metabolic responses to a 16-week intervention designed to improve insulin sensitivity (SI), adiposity, and inflammation in obese African-American and Latino adolescents. A total of 100 participants (African Americans: n = 48, Latino: n = 52; age: 15.4 ± 1.1 years, BMI percentile: 97.3 ± 3.3) were randomly assigned to interventions: control (C; n = 30), nutrition (N; n = 39, 1×/week focused on decreasing sugar and increasing fiber intake), or nutrition + strength training (N+ST; n = 31, 2×/week). The following were measured at pre- and postintervention: strength, dietary intake, body composition (dual-energy X-ray absorptiometry/magnetic resonance imaging) and glucose/insulin indexes (oral glucose tolerance test (OGTT)/intravenous glucose tolerance test (IVGTT)) and inflammatory markers. Overall, N compared to C and N+ST reported significant improvements in SI (+16.5% vs. −32.3% vs. −6.9% respectively, P < 0.01) and disposition index (DI: +15.5% vs. −14.2% vs. −13.7% respectively, P < 0.01). N+ST compared to C and N reported significant reductions in hepatic fat fraction (HFF: −27.3% vs. −4.3% vs. 0% respectively, P < 0.01). Compared to N, N+ST reported reductions in plasminogen activator inhibitor-1 (PAI-1) (−38.3% vs. +1.0%, P < 0.01) and resistin (−18.7% vs. +11.3%, P = 0.02). There were no intervention effects for all other measures of adiposity or inflammation. Significant intervention by ethnicity interactions were found for African Americans in the N group who reported increases in total fat mass, 2-h glucose and glucose incremental areas under the curve (IAUC) compared to Latinos (P’s < 0.05). These interventions yielded differential effects with N reporting favorable improvements in SI and DI and N+ST reporting marked reductions in HFF and inflammation. Both ethnic groups had significant improvements in metabolic health; however some improvements were not seen in African Americans.
doi:10.1038/oby.2010.343
PMCID: PMC3106142  PMID: 21293446
5.  Increased physical activity and reduced adiposity in overweight Hispanic adolescents 
Purpose
Objectives of this study were to examine 1) whether changes in total PA (counts/minute, cpm) and time spent in moderate to vigorous PA (MVPA) are associated with changes in adiposity and 2) whether energy intake influences the relationship between changes in PA and changes in adiposity in overweight Hispanic adolescents.
Methods
Analysis included 38 overweight (BMI ≥ 85th %ile) Hispanic adolescents with complete pre- and post-test data on relevant variables after participating in a 16-week intervention. The intervention treatment did not influence physical activity, so the sample was combined and randomization group was adjusted for in the analysis. Body composition by DEXA, 7-day physical activity by accelerometry, and dietary intake by 3-day diet records were assessed pre- and post-intervention.
Results
Within individuals, the mean increase of PA (n=19) and mean decrease of PA (n=19) was approximately 105 cpm. A 100 cpm increase in total PA was associated with a decrease of 1.3 kg fat mass and 0.8% body fat after adjusting for pre-test adiposity, PA, age, sex, and treatment (p < 0.05). Controlling for energy intake modestly strengthened the relationships between total PA and fat mass and percent body fat. Changes in MVPA were not related to changes in adiposity after controlling for total PA (p>0.05).
Conclusion
Increasing total PA by 28% (100 cpm) was associated with a decrease of 1.4 kg of fat mass and 1% body fat over 16 weeks in overweight Hispanic adolescents independent of intervention group assignment. Increases in total physical activity, as compared to MVPA, may be sufficient to improve body composition in overweight Hispanic adolescents.
doi:10.1249/MSS.0b013e3181b9c45b
PMCID: PMC3163456  PMID: 19952807
Obesity; children; Hispanic; accelerometer; youth; DEXA
6.  Relationships Between IGF-I and IGFBP-I and Adiposity in Obese African American and Latino Adolescents 
Obesity (Silver Spring, Md.)  2010;19(5):933-938.
The purpose of this study was to examine interrelationships between IGF-I, IGF binding proteins (IGFBPs), and adiposity in 49 African American and 77 Latino obese adolescents (15.3±0.1 and 15.4±0.2 yr; body mass index: 33.0±0.7 and 35.0±1.0 kg/m2, respectively). Immunoradiometric assays were used to measure IGF-I, IGFBP-I, and IGFBP-3. Total fat and soft lean tissue were measured by DEXA and visceral adipose tissue (VAT), subcutaneous abdominal adipose tissue (SAAT), and hepatic fat fraction (HFF) were measured by MRI. IGF-I levels were 23.1% higher and IGFBP-I were 40.4% higher in African Americans compared to Latinos after adjustment for total lean and total fat mass. IGF-I and IGFBP-I were inversely correlated with BMI, total fat mass, VAT, and HFF (r = −0.20 to −0.33, p<0.05) while IGFBP-I was inversely correlated with SAAT (r = −0.22, p<0.05). These relationships did not differ by ethnicity, however, the relationship between IGF-I and SAAT, as well as IGFBP-I and HFF, differed by ethnicity. Predicted mean IGF-I levels were 30.7% higher for African Americans at the 75th compared to 25th percentile of SAAT and only 11.7% higher for Latinos. Predicted mean IGFBP-I levels were 158% higher for African Americans at the 25th compared to the 75th percentile of HFF while IGFBP-I levels were 1.7% higher for Latinos at the 75th compared to the 25th percentile. These results demonstrate that the relationship between IGF-I and SAAT as well as IGFBP-I and HFF are different in African American and Latino adolescents and may contribute to the higher IGF-I levels in African Americans.
doi:10.1038/oby.2010.211
PMCID: PMC3081365  PMID: 20885383
Insulin-Like Growth Factors; Insulin-Like Growth Factor Binding Proteins; Ethnicity Differences; Obesity; Minorities
7.  Dietary Intake and the Metabolic Syndrome in Overweight Latino Children 
Little is known about the relationship between diet and metabolic health in Latino children, a population at increased risk for diabetes. The present study evaluates diet composition and the metabolic syndrome in a cross-sectional sample of 109 overweight Latino children aged 10 to 17 years with a family history of type 2 diabetes. Dietary intake was assessed by two 24-hour recalls. Associations between nutrients and features of the metabolic syndrome were examined using multiple linear regression and analysis of covariance. Log cholesterol intake was positively associated with log systolic blood pressure (β=0.034, P=0.017) and log soluble dietary fiber intake was inversely associated with log waist circumference (β=−0.069, P=0.036). Log soluble fiber intake was significantly higher in participants with 0 features compared to those with 3+ features of the metabolic syndrome (P=0.046), which translates to 5.2 g vs 4.1 g soluble fiber daily. No other significant associations were found between dietary variables and either the individual features of the metabolic syndrome or the clustering of metabolic syndrome components. Increases in soluble fiber through the daily consumption of fruits, vegetables, and beans may improve metabolic health in Latino children.
doi:10.1016/j.jada.2008.05.006
PMCID: PMC2882193  PMID: 18656576
8.  Randomized Control Trial to Improve Adiposity and Insulin Resistance in Overweight Latino Adolescents 
Obesity (Silver Spring, Md.)  2009;17(8):1542-1548.
Few randomized trials attempt to improve insulin sensitivity and associated metabolic risks in overweight Latino youth. The purpose of this study is to examine the effects of a modified carbohydrate nutrition program combined with strength training on insulin sensitivity, adiposity, and other type 2 diabetes risk factors in overweight Latino adolescents. In a 16-week randomized trial, 54 overweight Latino adolescents (15.5 ± 1.0 years) were randomly assigned to: (i) Control (C; n = 16), (ii) Nutrition (N; n = 21), or (iii) Nutrition + Strength training (N+ST; n = 17). The N group received modified carbohydrate nutrition classes (once per week), while the N+ST received the same nutrition classes plus strength training (twice per week). The following were measured at pre- and postintervention: strength by 1-repetition maximum, dietary intake by 3-day records, body composition by dual-energy X-ray absorptiometry, glucose/insulin indices by oral glucose tolerance test (OGTT) and intravenous glucose tolerance test with minimal modeling. Across intervention group effects were tested using analysis of covariance with post hoc pairwise comparisons. A significant overall intervention effect was found for improvement in bench press (P < 0.001) and reductions in energy (P = 0.05), carbohydrate (P = 0.04) and fat intake (P = 0.03). There were no significant intervention effects on insulin sensitivity, body composition, or most glucose/insulin indices with the exception of glucose incremental area under the curve (IAUC) (P = 0.05), which decreased in the N and N+ST group by 18 and 6.3% compared to a 32% increase in the C group. In conclusion, this intense, culturally tailored intervention resulted in no significant intervention effects on measured risk factors with the exception of a beneficial effect on glycemic response to oral glucose.
doi:10.1038/oby.2009.19
PMCID: PMC2846423  PMID: 19247280
9.  Aerobic and Strength Training Reduces Adiposity in Overweight Latina Adolescents 
Purpose
To date, no study has examined the synergistic effects of a nutrition and combination of aerobic and strength training (CAST) on both adiposity and metabolic parameters in overweight Latina adolescent females. The goal was to assess if a 16-wk nutrition plus CAST pilot study had stronger effects on reducing adiposity and on improving glucose/insulin indices compared with control (C), nutrition only (N), and a nutrition plus strength training (N + ST) groups.
Methods
In a 16-wk randomized trial, 41 overweight Latina girls (15.2 ± 1.1 yr) were randomly assigned to C (n = 7), N (n = 10), N + ST (n = 9), or N + CAST (n = 15). All intervention groups received modified carbohydrate nutrition classes (once a week), whereas the N + ST also received strength training (twice a week) and the N + CAST received a combination of strength and aerobic training (twice a week). The following were measured before and after intervention: strength by one repetition maximum, physical activity by the 7-d accelerometry and the 3-d physical activity recall, dietary intake by 3-d records, body composition by dual-energy x-ray absorptiometry (DEXA), glucose/insulin indices by oral glucose tolerance test, and intravenous glucose tolerance test with minimal modeling. Across intervention group, effects were tested using ANCOVA with post hoc pairwise comparisons.
Results
There were significant overall intervention effects for all adiposity measures (weight, body mass index [BMI], BMI z-scores, and DEXA total body fat), with a decrease of 3% in the N + CAST group compared with a 3% increase in the N + ST group (P ≤ 0.05). There was also an intervention effect for fasting glucose with the N group increasing by 3% and the N + CAST group decreasing by 4% (P ≤ 0.05).
Conclusion
The CAST was more effective than nutrition alone or nutrition plus strength training for reducing multiple adiposity outcomes and fasting glucose in overweight Latina girls. However, further research investigating and identifying intervention approaches that improve both adiposity and insulin indices, particularly in high-risk populations, are warranted.
doi:10.1249/MSS.0b013e31819b6aea
PMCID: PMC2836768  PMID: 19516150
EXERCISE; NUTRITION; INTERVENTION; OVERWEIGHT; TEENAGERS
10.  Dietary fiber and associations with adiposity and fasting insulin among college students with plausible dietary reports 
Objective
We examined the dietary fiber intake, food sources of dietary fiber, and relationship of dietary fiber with body composition and metabolic parameters in college students with plausible dietary reports.
Research Methods & Procedures
Students (18–24 yrs) provided data on anthropometry, fasting blood chemistries, and body composition (bioelectric impedance). Diet and physical activity were assessed with the Diet History Questionnaire and the International Physical Activity Questionnaire. Plausible dietary reporters were identified (± 1 SD cutoffs for reported energy intake as a percentage of predicted energy requirement). Multiple regression analyses were conducted with the total (n=298) and plausible (n=123) samples, adjusting for age, race, sex, smoking status, physical activity, energy intake, and fat free mass (where applicable).
Results
Food sources of dietary fiber were similar in males and females. In the plausible sample compared to the total sample, dietary fiber was more strongly associated with fat mass (β=−0.24, p<0.001), percent body fat (β= −0.23, p<0.001), BMI (β= −0.11, p<0.01), waist circumference (β= −0.67, p<0.05), and fasting insulin (β= −0.15, p<0.001). When the effect of sex was investigated, dietary fiber was inversely related to fasting insulin and fat mass in men and women and inversely related to percent body fat, BMI, and waist circumference in men only (p<0.05).
Conclusions
Inclusion of implausible dietary reports may result in spurious or weakened diet-health associations. Dietary fiber is negatively associated fasting insulin levels in males and females and consistently associated with adiposity measures in males.
doi:10.1016/j.nut.2009.02.003
PMCID: PMC2831808  PMID: 19403267
Diet; glucose; body composition; adults; health; food habits
11.  Cardiorespiratory fitness predicts changes in adiposity in overweight Hispanic boys 
Obesity (Silver Spring, Md.)  2008;16(5):1072-1077.
We have previously shown that cardiorespiratory fitness predicts increasing fat mass during growth in white and African-American youth, but limited data are available examining this issue in Hispanic youth. Study participants were 160 (53% boys) overweight (BMI ≥ 85th percentile for age and gender) Hispanic children (mean ± SD age at baseline =11.2 ± 1.7 yrs). Cardiorespiratory fitness, or VO2max, was measured via a maximal effort treadmill test at baseline. Body composition by dual-energy x-ray absorptiometry and Tanner stage by clinical exam were measured at baseline and annually thereafter for up to four years. Linear mixed models were used to examine the gender specific relationship between VO2max and increases in adiposity (change in fat mass independent of change in lean tissue mass) over four years. The analysis was adjusted for changes in Tanner stage, age, and lean tissue mass. In boys, higher VO2max at baseline was inversely associated with the rate of increase in adiposity (β= -0.001, p=0.03); this effect translates to a 15% higher VO2max at baseline resulting in a 1.38kg lower fat mass gain over four years. However, VO2max was not significantly associated with changes in fat mass in girls (β=0.0002, p=0.31). In overweight Hispanic boys, greater cardiorespiratory fitness at baseline was protective against increasing adiposity. In girls however, initial cardiorespiratory fitness was not significantly associated with longitudinal changes in adiposity. These results suggest that fitness may be an important determinant of changes in adiposity in overweight Hispanic boys but not in girls.
doi:10.1038/oby.2008.16
PMCID: PMC2780237  PMID: 18309303
Children; Youth; Longitudinal; Gender
12.  Interventions for improving metabolic risk in overweight Latino youth 
This review highlights various components of interventions that reduced obesity and type 2 diabetes risk factors among overweight Latino youth. A total of 114 overweight Latino adolescents completed one of four randomized controlled trials: 1) strength training (ST; boys only); 2) modified carbohydrate nutrition program (N); 3) combination of N+ST; or 4) N + Combination of Aerobic and ST (N+CAST; girls only). Measures included: strength by 1-repetition max, dietary intake by 3-d records, body composition by DEXA/MRI, glucose/insulin indices by oral and IV glucose tolerance tests. ST improved insulin sensitivity by 45% in Latino boys, and N, N+ST, and N+CAST improved glucose control in Latino boys and girls. The CAST approach reduced all adiposity measures by ∼3% in Latina girls. Participants who decreased added sugar, increased dietary fiber, and had increased parental attendance, regardless of intervention group, improved insulin action and reduced visceral adipose tissue. In conclusion, ST, CAST, and a modified carbohydrate nutrition program with separate parental classes were all successful components of the interventions that decreased obesity and related metabolic diseases.
doi:10.3109/17477161003770123
PMCID: PMC3752963  PMID: 20387989
Latino adolescents; randomized controlled trials; insulin sensitivity and secretion; diet and exercise interventions; adiposity

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