Showing papers by "Barbara A. Gower published in 2009"

Effect of dietary adherence with or without exercise on weight loss: a mechanistic approach to a global problem.

Abstract: Context: Weight loss using low-calorie diets produces variable results, presumably due to a wide range of energy deficits and low-dietary adherence. Objective: Our objective was to quantify the relationship between dietary adherence, weight loss, and severity of caloric restriction. Design and Setting: Participants were randomized to diet only, diet-endurance training, or diet-resistance training until body mass index (BMI) was less than 25 kg/m2. Participants: Healthy overweight (BMI 27–30) premenopausal women (n = 141) were included in the study. Interventions: An 800-kcal/d−1 diet was provided, and the exercise groups were engaged in three sessions per week. Main Outcomes: Dietary adherence, calculated from total energy expenditure determined by doubly labeled water measurements and dual-energy x-ray absorptiometry body composition changes, and degree of caloric restriction were determined. Results: All groups had similar weight loss (∼12.1 ± 2.5 kg) and length of time to reach target BMI (∼158 ± 70 d)...

Threshold for Effects of Vitamin D Deficiency on Glucose Metabolism in Obese Female African-American Adolescents

Abstract: Context: Vitamin D status can influence insulin resistance. Objective: The aim of the study was to determine the prevalence of vitamin D deficiency in obese African-American (AA) adolescent females in a southeastern latitude and to determine the relationship of 25-hydroxyvitamin D [25(OH)D] with insulin and glucose dynamics. Design: We conducted a cross-sectional study in a University Children’s Hospital. Methods: Serum 25(OH)D, fasting glucose, PTH, serum calcium, serum lipids, serum transaminases, and C-reactive protein were assessed. Indices of insulin sensitivity and resistance were determined from an oral glucose tolerance test. Subjects were classified as vitamin D deficient or sufficient, based on the traditional vitamin D deficiency definition [serum 25(OH)D <20 ng/ml] and also by a lower 25(OH)D cut-point of 15 ng/ml or less. Results: A total of 51 AA adolescent females (body mass index, 43.3 ± 9.9 kg/m2; age, 14 ± 2 yr) were studied. Serum 25(OH)D concentrations were 20 ng/ml or less in 78.4% and 15 ng/ml or less in 60.8% of subjects. There were no significant group differences in the metabolic outcomes when subjects were classified using the traditional vitamin D deficiency definition. The Matsuda index of insulin sensitivity was significantly lower (P = 0.02), and insulin area under the curve was significantly higher (P = 0.04) in subjects with 25(OH)D concentrations of 15 ng/ml or less vs. those with higher concentrations. Conclusions: Vitamin D deficiency is highly prevalent in obese, AA female adolescents and may promote insulin resistance. Our data suggest that a 25(OH)D concentration of 15 ng/ml or less may be the threshold by which vitamin D deficiency confers negative effects on insulin sensitivity.

Utility of waist circumference percentile for risk evaluation in obese children

Abstract: 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 o...

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

Abstract: 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 P P P P P 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.

Insulin Sensitivity in African‐American and White Women: Association With Inflammation

Abstract: Whether the contribution of inflammation to risk for chronic metabolic disease differs with ethnicity is not known. The objective of this study was to determine: (i) whether ethnic differences exist in markers of inflammation and (ii) whether lower insulin sensitivity among African Americans vs. whites is due to greater inflammatory status. Subjects were African-American (n = 108) and white (n = 105) women, BMI 27–30 kg/m2. Insulin sensitivity was assessed with intravenous glucose tolerance test and minimal modeling; fat distribution with computed tomography; body composition with dual-energy X-ray absorptiometry; markers of inflammation (tumor necrosis factor (TNF)-α, soluble tumor necrosis factor receptor (sTNFR)-1, sTNFR-2, C-reactive protein (CRP), and interleukin (IL)-6) with enzyme-linked immunosorbent assay (ELISA). Whites had greater intra-abdominal adipose tissue (IAAT), insulin sensitivity, and concentrations of TNF-α, sTNFR-1, and sTNFR-2 than African Americans. Greater TNF-α in whites vs. African Americans was attributed to greater IAAT in whites. Among whites, but not African Americans, CRP was independently and inversely associated with insulin sensitivity, after adjusting for IAAT (r = −0.29 P < 0.05, and r = −0.13 P = 0.53, respectively). Insulin sensitivity remained lower in African Americans after adjusting for CRP (P < 0.001). In conclusion, greater IAAT among whites may be associated with greater inflammation. Insulin sensitivity was lower among African Americans, independent of obesity, fat distribution, and inflammation.

Effects of Low- and High-Glycemic Index/Glycemic Load Diets on Coronary Heart Disease Risk Factors in Overweight/Obese Men

Abstract: Chronic insulin resistance contributes to subclinical inflammation, thrombosis/impaired fibrinolysis, and dyslipidemia. The effect of dietary carbohydrate, specifically of glycemic index (GI) and glycemic load (GL), on established and emerging coronary heart disease risk factors has not been elucidated fully. We conducted a randomized crossover feeding study of matched diets differing only in GI and GL in 24 overweight or obese but otherwise healthy men to investigate the effects on insulin sensitivity, inflammation, thrombosis/fibrinolysis, lipoproteins/lipids, and body composition. All meals for the high- and low-GI/GL diets were prepared in a metabolic kitchen. Each participant consumed both diets in random order for 4 weeks each, with a 4-week washout period in between. Each participant underwent a frequently sampled intravenous glucose tolerance test for assessment of insulin sensitivity; blood sampling for the measurement of inflammatory markers, coagulation factors, and lipoproteins/lipids; and dual-energy x-ray absorptiometry for assessment of body composition at the beginning and end of each dietary period. There were no statistically significant differences in glucose metabolism factors, inflammatory markers, or coagulation factors after 4 weeks on the high- and low-GI/GL diets. The high-GI/GL diet resulted in a slightly greater reduction in fat mass and a slightly greater increase in lean mass compared with the low-GI/GL diet. The high-GI/GL diet resulted in significant, but unexpected, reductions in total and low-density lipoprotein cholesterol, whereas high-density lipoprotein cholesterol concentration was significantly reduced on the high-GI/GL diet compared with the low-GI/GL diet. Overall, high- and low-GI/GL diets of 4 weeks' duration had no consistent effects on coronary heart disease risk factors in this group of overweight/obese men.

Physical activity may facilitate diabetes prevention in adolescents.

Abstract: OBJECTIVE—The aim of this study was to examine the association of physical activity with glucose tolerance and resting energy expenditure (REE) among adolescents. RESEARCH DESIGN AND METHODS—Subjects were 32 male and female adolescents aged 12–18 years. Intravenous glucose tolerance (Kg) and REE were assessed under inpatient conditions after an overnight fast. Kg was determined as the inverse slope of time versus (ln) glucose over minutes 8–19 of an intravenous glucose tolerance test. Physical activity was assessed over 8 days using accelerometry (counts per minute). RESULTS—In multiple linear regression analysis, Kg was positively associated with total physical activity (TPA), moderate physical activity (MPA), and 5-min bouts of MPA. Similarly, REE was positively associated with TPA, MPA, and 5-min bouts of MPA. CONCLUSIONS—In this population, physical activity was positively related to both glucose tolerance and REE. These results suggest that moderate activity may be beneficial in the prevention of diabetes in adolescent populations both through promoting efficient glucose disposal and through increasing energy expenditure.

High-Milk Supplementation with Healthy Diet Counseling Does not Affect Weight Loss but Ameliorates Insulin Action Compared with Low-Milk Supplementation in Overweight Children

Abstract: Milk consumption has decreased in children over the past years. This may play a role in the prevalence of pediatric obesity, because clinical studies have found a beneficial effect of milk consumption for weight management. The objectives of this study were to test whether high-milk consumption leads to greater weight loss and improvements in metabolic risk factors than low milk consumption during a 16-wk healthy eating diet. Overweight children aged 8-10 y were randomized to either high (4 x 236 mL/d) or low (1 x 236 mL/d) milk consumption. Children were provided dietary counseling on healthy eating at baseline and at wk 1, 2, 4, 6, 8, and 12. Serum glucose, insulin, and lipids were measured in fasting children at baseline and wk 8 and 16. An oral glucose tolerance test and body composition assessment by magnetic resonance imaging were conducted at baseline and endpoint. Body weight changes during the 16-wk study not differ between the high-milk (1.3 +/- 0.3 kg) and low-milk (1.1 +/- 0.3 kg) groups. There was no beverage x week interaction on any of the body composition and metabolic variables studied (blood pressure, serum lipids, glucose, and insulin). There was a beverage x week interaction (P = 0.044) on insulin area under the curve showing a trend toward reduced insulin output with a glucose challenge after high-milk consumption (P = 0.062). These data suggest that in overweight children, high-milk consumption in conjunction with a healthy diet does not lead to greater weight loss but may ameliorate insulin action compared with low-milk consumption.

High-Milk Supplementation with Healthy Diet Counseling Does not Affect Weight Loss but Ameliorates Insulin Action Compared with Low-Milk Supplementation in

Abstract: Milk consumption has decreased in children over the past years. This may play a role in the prevalence of pediatric obesity, because clinical studies have found a beneficial effect of milk consumption for weight management. The objectives of this study were to test whether high-milk consumption leads to greater weight loss and improvements in metabolic risk factors than low milk consumption during a 16-wk healthy eating diet. Overweight children aged 8‐10 y were randomized to either high (4 3 236 mL/d) or low (1 3 236 mL/d) milk consumption. Children were provided dietary counseling on healthy eating at baseline and at wk 1, 2, 4, 6, 8, and 12. Serum glucose, insulin, and lipids were measured in fasting children at baseline and wk 8 and 16. An oral glucose tolerance test and body composition assessment by magnetic resonance imaging were conducted at baseline and endpoint. Body weight changes during the16-wk study not differ between the high-milk (1.3 6 0.3 kg) and low-milk (1.1 6 0.3 kg) groups. There was no beverage 3week interaction on any of the body composition and metabolic variables studied (blood pressure, serum lipids, glucose, and insulin). There was a beverage 3 week interaction (P ¼ 0.044) on insulin area under the curve showing a trend toward reduced insulin output with a glucose challenge after high-milk consumption (P ¼ 0.062). These data suggest that in overweight children, highmilk consumption in conjunction with a healthy diet does not lead to greater weight loss but may ameliorate insulin action compared with low-milk consumption. J. Nutr. 139: 933‐938, 2009.

Perception of others' body size influences weight loss and regain for European American but not African American women.

Abstract: Objective: The authors investigated whether European American (EA) and African American (AA) women took longer to lose weight, and were less likely to maintain weight loss if they perceived others to be overweight. Design: Overweight EA and AA women completed a Figure Rating Scale and the Three-Factor Eating Questionnaire prior to a weight loss intervention. Body composition was assessed by dual energy X-ray absorptiometry prior to and following weight loss. Main Outcome Measures: rate of weight loss, % body fat at follow-up. Results: For EA, but not AA women, perception of others' body size was inversely associated with rate of weight loss and cognitive restraint, and positively associated with body fat gain following intervention. In linear regression modeling, EA, but not AA, women who perceived others as large, subsequently had greater percent body fat 1 year after weight loss than did those who perceived others as lean, independent of age, baseline body fat, and body size deemed "acceptable." Inclusion of cognitive restraint in the model weakened this effect. Conclusion: Among EA but not AA women, perception of others' body size influenced weight loss and maintenance. This effect may have been mediated by cognitive restraint.

Physical fitness, activity, and insulin dynamics in early pubertal children.

Abstract: The objectives of this study were to identify the independent effect of physical activity and fitness on insulin dynamics in a cohort of European-, African-, and Hispanic-American children (n = 215) age 7-12 years and to determine if racial/ethnic in insulin dynamics could be statistically explained by racial/ethnic differences in physical activity or fitness. An intravenous glucose tolerance test and minimal modeling were used to derive the insulin sensitivity index (SI) and acute insulin response to glucose (AIRg). Fitness was assessed as VO2-170 and physical activity by accelerometer. Multiple regression models were tested for contributions of fitness and physical activity to SI and AIRg. Fitness was a stronger predictor of SI and AIRg than physical activity regardless of ethnicity; racial/ethnic differences in insulin dynamics were not accounted for by differences in fitness and/or physical activity.

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

Abstract: The alarming rise in the prevalence of obesity among the pediatric population has become one of the most serious and urgent public health problems. Many of the metabolic complications associated with obesity are already present during childhood and are closely linked to risk for the development of type 2 diabetes and cardiovascular disease. Excess adiposity is strongly associated with reduced insulin sensitivity, impaired glucose tolerance, adverse lipid profiles and elevated blood pressure in both adult (1–3) and pediatric (4–8) populations. However, the location of the excess body fat may differentially influence the severity of metabolic complications. Intra-abdominal adipose tissue (IAAT), in particular, has been shown to be strongly correlated with insulin dynamics and lipid metabolism in adults (1;9;10). Studies in adult humans as well as in animal models indicate that compared to the subcutaneous fat depot, IAAT is a greater contributor to adverse cardiometabolic outcomes (1;9;10). Information on the adverse effects of IAAT in children, especially early pubertal children, is limited. Adipose tissue is preferentially deposited subcutaneously in early pubertal children and IAAT is relatively low among this group (6;11). However, it has been hypothesized that beginning in childhood, as excess fat begins to accumulate, lipid overflow leads to increasing fat deposition into the IAAT compartment that may initiate cardiometabolic complications (5;12). The regional distribution of adipose tissue appears to influence cardiometabolic outcomes, specifically glucose and lipid metabolism and blood pressure (1). It is not clear if specific fat depots contribute to cardiometabolic outcomes differently in children, particularly children of diverse racial/ethnic backgrounds. It has been clearly demonstrated that Hispanic and African Americans of every age group are disproportionately affected by cardiovascular disease and type 2 diabetes relative to their European American counterparts (13–15). Part of this ethnic discrepancy in disease risk may derive from ethnic differences in fat distribution. Racial/ethnic differences in body fat distribution as well as in metabolic risk factors have been identified in both adults and children. Hispanic American adults (5;16) and children (5) reportedly have greater IAAT than European Americans even when matched for total adiposity. More adverse cardiometabolic outcomes observed in Hispanic Americans relative to European Americans appears to be reflective of greater fat accumulation, particularly in the intra-abdominal compartment. Unlike Hispanics, African American adults and children have been consistently shown to have less IAAT than European Americans for a given total body fat (1;3;11;17;18). Further, greater risk for type 2 diabetes among African Americans vs. European Americans is independent of BMI (14). Taken together, these observations suggest that either there are factors unrelated to adiposity underlying metabolic risk, or that the threshold for an effect of a given adipose tissue depot on metabolic risk may be lower among African Americans. Few studies (4;6;11;19) have investigated the associations among fat depots and metabolic outcomes in children. To our knowledge no study has investigated these variables using robust measures of metabolism and body composition in a multi-ethnic cohort of early pubertal children. The aim of this study was to examine the associations of individual adipose depots with metabolic outcomes, and whether these associations vary by race/ethnicity or sex.

Obesity attenuates the contribution of African admixture to the insulin secretory profile in peripubertal children: a longitudinal analysis.

Abstract: The pubertal transition has been identified as a time of risk for development of type 2 diabetes, particularly among vulnerable groups, such as African Americans (AAs). Documented ethnic differences in insulin secretory dynamics may predispose overweight AA adolescents to risk for type 2 diabetes. The objectives of this longitudinal study were to quantify insulin secretion and clearance in a cohort of 90 AA and European American (EA) children over the pubertal transition and to explore the association of genetic factors and adiposity with repeated measures of insulin secretion and clearance during this critical period. Insulin sensitivity was determined by intravenous glucose tolerance test (IVGTT) and minimal modeling; insulin secretion and clearance by C-peptide modeling; genetic ancestry by admixture analysis. Mixed-model longitudinal analysis indicated that African genetic admixture (AfADM) was independently and positively associated with first-phase insulin secretion within the entire group (P < 0.001), and among lean children (P < 0.01). When examined within pubertal stage, this relationship became significant at Tanner stage 3. Total body fat was a significant determinant of first-phase insulin secretion overall and among obese children (P < 0.001). Total body fat, but not AfADM, was associated with insulin clearance (P < 0.001). In conclusion, genetic factors, as reflected in AfADM, may explain greater first-phase insulin secretion among peripubertal AA vs. EA; however, the influence of genetic factors is superseded by adiposity. The pubertal transition may affect the development of the β-cell response to glucose in a manner that differs with ethnic/genetic background.

Relationships between reported macronutrient intake and insulin dynamics in a multi-ethnic cohort of early pubertal children.

Abstract: Background. Racial/ethnic differences in the pediatric population in insulin dynamics have been documented. Additionally, girls tend to be more insulin resistant than boys. Although the mechanism d...

Uncoupling Protein 2 Ala55Val polymorphism is associated with a higher acute insulin response to glucose

Abstract: Recent evidence suggests that mitochondrial uncoupling protein 2 (UCP2) in pancreatic beta-cells plays a crucial role in insulin production and secretion. We hypothesized that 2 UCP2 polymorphisms, a -55C/T (Ala55Val) substitution in exon 4 and an exon 8 insertion, would alter the acute insulin response to glucose (AIRg). Subjects were 155 African American (AA) and European American (EA) women. Body composition was determined by dual-energy x-ray absorptiometry. Insulin sensitivity and AIRg were measured with an intravenous glucose tolerance test and minimal modeling. To account for the confounding effects of population stratification, estimates of African admixture were obtained from approximately 35 ancestry-informative markers. Uncoupling protein 2 genotyping was conducted with gel electrophoresis. Information was analyzed using mixed linear models. A positive association between the -55C/T homozygous mutation and AIRg was identified in the total sample (P < .01) and independently in EA women (P = .02) but not AA women. The exon 8 insertion did not significantly affect AIRg. No interaction effects of the 2 polymorphisms on AIRg were noted. These results indicate that AIRg is associated with the -55C/T UCP2 homozygous mutation and that the presence of this mutation could alter postchallenge insulin concentration.

Triglyceride Concentration is Independently Associated with Variation inthe LPL Gene in African American and European American Women

Abstract: Objective: The regulation of triglyceride (TG) metabolism may be affected by many factors including: race/ethnicity, body composition, body fat distribution, insulin action, and the activity of the lipoprotein lipase (LPL) enzyme. This study was designed to identify the independent effects of body composition, body fat distribution, insulin action, and LPL genetic variation on TG and HDL-C concentration. Subjects: The study consisted of premenopausal European American (EA) (n=114) and African American (AA) (n=140) women. Measurements: Body composition was measured by dual-energy X-ray absorptiometry (DXA), intra-abdominal adipose tissue (IAAT) by computed tomography (CT), insulin sensitivity (SI) and the acute insulin response to glucose (AIRg) by intravenous glucose tolerance test, median household income by zip-code. An estimate of individual genetic admixture was obtained from the genotyping of 85 ancestry informative markers and used to control for population stratification. Multiple linear regression analyses were used to identify contributions of body composition, IAAT, SI, AIRg, African genetic admixture, and LPL polymorphisms to TG and HDL-C. Results: AA had lower TG and higher HDL-C than EA. African genetic admixture, IAAT, AIRg, SI, and RS285 were significantly and independently related to TG concentration. SI was the only independent contributor to HDL-C. RS1800590 was not associated with variation in TG or HDL. Conclusion: Triglyceride concentration appears to be multifactorial in origin and emanates in part from variance in LPL RS285. Future investigations are necessary to understand the mechanisms through which gene polymorphisms, body fat distribution, and insulin action influence the lipid profile.

Characterization of the Metabolic Syndrome in a Multi-Ethnic Sample of Children: Is it Useful?

Abstract: The pathophysiological relevance of the metabolic syndrome is not currently understood, particularly when attempting to apply the diagnosis to children with varying degrees of adiposity or from ethnically diverse populations. The aim of this study was to evaluate the applicability of the metabolic syndrome characterization when the associations are explored by sex, race/ethnicity, and weight status. Participants were 247 multi-ethnic (African American (AA); n=90; European American (EA); n=102; Hispanic American (HA); n=55) children aged 7-12y. Anthropometric measurements, body composition, blood pressure and fasting blood samples were obtained. Approximately 9% of the children met the criteria for a clinical diagnosis of the metabolic syndrome. There were no differences in prevalence by sex, nor were there differences between girls and boys for mean values of each component. However, there were ethnic differences in characterization of having the metabolic syndrome, with HA more likely to meet the criteria. HA had greater waist circumference, higher triglyceride and glucose concentration and lower HDL-C concentration; whereas AA had higher blood pressure. Weight status was also positively associated with mean values for each component. Due to inherent variations in body composition, physiology and genetics, the usefulness of a characterization of the metabolic syndrome may be limited in the pediatric population.