Showing papers by "Barbara A. Gower published in 2001"
TL;DR: Pubertal transition from Tanner stage I to Tanner stage III was associated with a 32% reduction in S(I,) and increases in fasting glucose, insulin, and AIR, and these changes were similar across sex, ethnicity, and obesity.
Abstract: Previous cross-sectional studies show that puberty is associated with a reduction in insulin sensitivity (S(I)), but no longitudinal studies have examined this change in detail. This study is a longitudinal study in 60 children (33 male and 27 female subjects; 32 Caucasian and 28 African-American) examined at Tanner stage I (age 9.2 +/- 1.4 years) and after 2.0 +/- 0.6 years of follow-up, by which time 29 children remained at Tanner stage I and 31 had progressed to Tanner stage III or IV. Tanner stage was assessed by physical examination. S(I), the acute insulin response (AIR), and the disposition index (DI) were determined by the tolbutamide-modified intravenous glucose tolerance test and minimal modeling, body fat mass was assessed by dual-energy X-ray absorptiometry, visceral fat was determined by computed tomography, and fasting blood was analyzed for hormone levels. In children progressing to Tanner stage III, S(I) fell significantly by 32% (4.4 +/- 3.0 to 3.0 +/- 1.7 x 10(-4)min(-1)/[microIU/ml]), AIR increased by 30%, DI fell by 27%, and there was a significant increase in fasting glucose (93.5 +/- 5.0 to 97.0 +/- 4.1 mg/dl) and insulin (14.3 +/- 8.1 to 18.6 +/- 11.0 microIU/ml). In children remaining at Tanner stage I, there was a slight increase in S(I) (6.4 +/- 3.1 to 7.4 +/- 3.5 x 10(-4)min(-1)/[microIU/ml]) with no significant change in AIR or fasting glucose and insulin. The pubertal fall in S(I) was more consistent in African-Americans; remained significant after controlling for age, sex, and change in fat mass, visceral fat, and fat-free mass; and was similar in children at low, medium, and high body fat. Change in S(I) was not significantly related to change in fasting hormone levels, but change in AIR was significantly related to change in androstendione (r = 0.39; P = 0.04). Pubertal transition from Tanner stage I to Tanner stage III was associated with a 32% reduction in S(I,) and increases in fasting glucose, insulin, and AIR. These changes were similar across sex, ethnicity, and obesity. The significant fall in DI suggests conservation in beta-cell function or an inadequate beta-cell response to the fall in S(I). The fall in S(I) was not associated with changes in body fat, visceral fat, IGF-I, androgens, or estradiol.
658 citations
TL;DR: Results indicate that a single bout of mechanical loading in humans alters activity of the muscle IGF-I system, and the enhanced response to ECC suggests that IGF- I may somehow modulate tissue regeneration after mechanical damage.
Abstract: The mechanism(s) of load-induced muscle hypertrophy is as yet unclear, but increasing evidence suggests a role for locally expressed insulin-like growth factor I (IGF-I). We investigated the effect...
351 citations
TL;DR: The cut-points describe an adequate health-related definition of childhood obesity and indicate that children with > or =33% body fat and children with a waist circumference> or =71 cm were more likely to possess an adverse CVD risk-Factor profile than a normal risk-factor profile.
Abstract: HIGGINS, PAUL B., BARBARA A. GOWER, GARY R. HUNTER, AND MICHAEL I. GORAN. Defining health-related obesity in prepubertal children. Obes Res. 2001;9:233‐240. Objective: The purpose of this study was to develop percentage of fat and waist circumference cut-points in prepubertal children with the intention of defining obesity associated with cardiovascular disease (CVD) risk. Research Methods and Procedures: A cross-sectional analysis of 87 prepubertal children aged 4 to 11 years was used. Percentage of body fat was determined by DXA. Waist circumference was measured to the nearest millimeter. Receiver Operating Characteristic analyses of percentage of fat and waist circumference were used to develop cut-points for individuals with adverse levels of CVD risk factors. Results: The risk factors selected for analyses (i.e., fasting insulin, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, and total cholesterol/ high-density lipoprotein cholesterol) were significantly related to percentage of body fat and waist circumference. Likelihood ratios were used to identify percentage of fat and waist circumference cut-points associated with adverse cardiovascular risk profiles. Two cut-points, an upper cut-point of 33% body fat and a lower cut-point of 20% body fat, were derived. Waist circumference cut-points indicative of adverse and normal risk-factor profiles were 71 cm and 61 cm, respectively. Discussion: The data indicate that children with $33% body fat and children with a waist circumference $71 cm were more likely to possess an adverse CVD risk-factor profile than a normal risk-factor profile. The likelihood of children with ,20% body fat or a waist circumference ,61 cm possessing an adverse CVD risk-factor profile as opposed to a normal risk-factor profile was small. The cutpoints describe an adequate health-related definition of childhood obesity.
158 citations
TL;DR: Body fat in general is the predominant factor influencing Si, but VFAT may have additional effects on fasting insulin, and the lack of major effects of VfAT on Si in children may be explained by lower levels of VFatin or because VFat affects aspects of whole body insulin action that are not measured by the minimal model.
Abstract: GORAN, MICHAEL I., RICHARD N. BERGMAN, AND BARBARA A. GOWER. Influence of total vs. visceral fat on insulin action and secretion in African American and white children. Obes Res. 2001;9:423‐ 431. Objective: To examine whether total body fat (FAT) in general or visceral fat (VFAT) in particular is associated with greater metabolic risk in white and African American children. Research Methods and Procedures: A total of 68 white and 51 African American children had measures of insulin sensitivity (Si) and acute insulin response (AIR) by a frequently sampled intravenous glucose tolerance test, total body fat by DXA and abdominal fat distribution (visceral vs. subcutaneous) by computed tomography. The influence of FAT and VFAT on insulin parameters were examined by comparing subgroups of children with high or low FAT vs. high or low VFAT and by multiple regression analysis. Results: In whites, fasting insulin, Si, and AIR were significantly influenced by FAT, but not VFAT (e.g., for Si, 9.8 6 0.8 in low FAT vs. 4.6 6 0.7 3 10 24 /min/[mIU/mL[ in high FAT, p , 0.05; 6.8 6 0.7 in low VFAT vs. 7.5 6 0.8 3 10 24 /min/[mIU/mL] in high VFAT, p . 0.1). In African Americans, fasting insulin and Si were also primarily influenced by FAT (e.g., for Si, 4.9 6 0.4 in low FAT vs. 2.8 6 0.5 3 10 24 /min/[mIU/mL] in high FAT, p , 0.05) but not by VFAT, and there were no significant effects of either fat compartment on AIR. In multiple regression analysis, Si was significantly influenced by FAT (negative effect), ethnicity (lower in African Americans), and gender (lower in females), whereas fasting insulin was significantly influenced by VFAT (positive effect), ethnicity (higher in African Americans), and fat free mass (positive effect). Discussion: Body fat in general is the predominant factor influencing Si, but VFAT may have additional effects on fasting insulin. The lack of major effects of VFAT on Si in children may be explained by lower levels of VFAT or because VFAT affects aspects of whole body insulin action that are not measured by the minimal model.
120 citations
TL;DR: Despite comparable decreases in total and trunk fat, white women lost more IAAT and less SAAT than did black women and Waist circumference was not a suitable surrogate marker for tracking changes in the visceral fat compartment in black women.
111 citations
TL;DR: T trunk lean mass (presumably primarily organ tissue) is relatively resistant to age-related changes in body composition, whereas muscle mass, especially leg muscle, tends to be lost.
86 citations
TL;DR: In a large sample of children at various Tanner stages, an ethnic difference in REE after adjustment for age, Tanner stage, FM, and LM that was not explained by the difference in LM distribution was found.
78 citations
TL;DR: A significant underestimation of percentage of body fat was observed with the presence of facial hair and scalp hair, which may be caused by the effect of trapped isothermal air in body hair on body-volume estimates.
Abstract: Objective: The objective of this study was to determine the effect of body hair (scalp and facial) on air displacement plethysmography (BOD POD) estimates of percentage of body fat.
Research Methods and Procedures: A total of 25 men (31.4 ± 8.0 years, 83.4 ± 12.2 kg, 181.8 ± 6.9 cm) agreed to grow a beard for 3 weeks to participate in the study. Total body density (g/cm3) and percentage of body fat were evaluated by BOD POD. To observe the effect of trapped isothermal air in body hair, BOD POD measures were performed in four conditions: criterion method (the beard was shaven and a swimcap was worn), facial hair and swimcap, facial hair and no swimcap, and no facial hair and no swimcap.
Results: The presence of only a beard (facial hair and swimcap) resulted in a significant underestimation of percentage of body fat (16.2%, 1.0618 g/cm3) vs. the criterion method (17.1%, 1.0597 g/cm3, p < 0.001). The effect of scalp hair (no swim cap worn) resulted in a significant underestimation in percentage of body fat relative to the criterion method, either with facial hair (facial hair and no swimcap; 14.8%, 1.0649 g/cm3) or without facial hair (no facial hair and no swimcap; 14.8%, 1.0650 g/cm3, p < 0.001 for both).
Discussion: A significant underestimation of percentage of body fat was observed with the presence of facial hair (∼1%) and scalp hair (∼2.3%). This underestimation in percentage of body fat may be caused by the effect of trapped isothermal air in body hair on body-volume estimates. Thus, excess facial hair should be kept to a minimum and a swimcap should be worn at all times to ensure accurate estimates of body fat when using the BOD POD.
78 citations
TL;DR: In prepubertal children, neither body fat nor fat distribution explain the ethnic difference in TAG or Lp(a), but visceral fat and TAG may contribute to differences in HDL-C.
Abstract: OBJECTIVE: The purpose of the present study was to determine the impact of body fat mass and fat distribution on serum lipids, lipoproteins and apolipoproteins in African-American and Caucasian-American prepubertal children. SUBJECTS: Study participants included 62 African-American children (age 8.3 1.4 y; body mass 37.3 13.6 kg; height 133 11 cm) and 39 Caucasian children (age 8.6 1.2 y; body mass 34.1 11.0 kg; height 131 9 cm). METHODS: Venous blood samples were obtained after a 12 h overnight fast and serum was analyzed for total cholesterol (TC), high-density lipoprotein-cholesterol (HDL-C), triacylglycerol (TAG), apolipoprotein A-I (ApoA-I), apolipoprotein B (ApoB) and lipoprotein (a) (Lp(a)) concentrations. Body composition and body fat distribution were measured by dual-energy X-ray absorptiometry and computed tomography, respectively. RESULTS: African-American children had lower TAG (46 20 vs 61 32 mg=dl, Pa 0.015) and higher Lp(a) (34 25 vs 17 28 mg=dl, Pa 0.001) and HDL-C (44 11 vs 39 8m g=dl, Pa 0.041). There were no ethnic differences in TC, ApoA-I and ApoB (Pa 0.535, Pa 0.218, Pa 0.418, respectively). The ethnic difference in TAG and Lp(a) was not explained by total fat or abdominal fat. The ethnic difference in HDL-C was explained by visceral fat and TAG. CONCLUSION: In prepubertal children, neither body fat nor fat distribution explain the ethnic difference in TAG or Lp(a), but visceral fat and TAG may contribute to differences in HDL-C. International Journal of Obesity (2001) 25, 198 ‐ 204
38 citations
3 citations