Assessment of Cardiac Autonomic Modulation during Adolescent Obesity

Objective: To investigate the cardiovascular autonomic function in pediatric obesity of different duration by using standard time domain, spectral heart rate variability (HRV), and nonlinear methods. Research Methods and Procedures: Fifty obese children (13.9 ± 1.7 years) were compared with 12 lean subjects (12.9 ± 1.6 years). Obese children were classified as recent obese (ROB) (<4 years), intermediate obese (IOB) (4 to 7 years), and long‐term obese (OB) (>7 years). In all participants, we performed blood pressure (BP) measurements, laboratory tests, and 24‐hour electrocardiogram/ambulatory BP monitoring. The spectral power was quantified in total power, very low‐frequency (LF) power, high‐frequency (HF) power, and LF to HF ratio. Total, long‐term, and short‐term time domain HRV were calculated. Poincaré plot and quadrant methods were used as nonlinear techniques. Results: All obese groups had higher casual and ambulatory BP and higher glucose, homeostasis model assessment, and triglyceride levels. All parameters reflecting parasympathetic tone (HF band, root mean square successive difference, proportion of successive normal‐to‐normal intervals, and scatterplot width) were significantly and persistently reduced in all obese groups in comparison with lean controls. LF normalized units, LF/HF, and cardiac acceleration (reflecting sympathetic activation) were significantly increased in the ROB group. In IOB and OB groups, LF, but not nonlinear, measures were similar to lean controls, suggesting biphasic behavior of sympathetic tone, whereas nonlinear analysis showed a decreasing trend with the duration of obesity. Long‐term HRV measures were significantly reduced in ROB and IOB. Discussion: Autonomic nervous system changes in adolescent obesity seem to be related to its duration. Nonlinear methods of scatterplot and quadrant analysis permit assessment of autonomic balance, despite measuring different aspects of HRV.     

Baroreflex sensitivity in obesity: relationship with cardiac autonomic nervous system activity

Objective: The aim of this study was to test the hypothesis that baroreflex sensitivity (BRS), assessed by indirect measurement of aortic pressure, is blunted in obesity. Additionally, the potential effect of cardiac autonomic nervous system (ANS) activity, aortic compliance, and metabolic parameters on BRS of obese subjects was investigated. Research Methods and Procedures: A group of 30 women with BMI >30 kg/m² and a group of 30 controls with BMI <25 kg/m² were examined. BRS was estimated by the sequence technique, cardiac ANS activity by short‐term spectral analysis of heart rate variability (HRV), and aortic compliance by the method of applanation tonometry. Results: BRS was lower in obese women (9.18 ± 3.77 vs. 19.63 ± 9.16 ms/mm Hg, p < 0.001). The median values (interquartile range) of the power of both the high‐frequency and low‐frequency components of the HRV were higher in the lean than in the obese participants [1079.2 (202.7 to 1716.9) vs. 224.1 (72.7 to 539.6) msec², p = 0.001 and 411.8 (199.3 to 798.0) vs. 235.8 (99.4 to 424.5) msec², p = 0.01 respectively]. Low‐to‐high‐frequency ratio values were higher in the obese subjects [0.82 (0.47 to 2.1) vs. 0.57 (0.28 to 0.89), p = 0.02]. Aortic augmentation values were not significantly different between lean and obese subjects. Multivariate analysis demonstrated a significant and independent association between BRS and age (p = 0.003), BMI (p < 0.001), and high‐frequency power of HRV (p < 0.001). These variables explained 72% of the variation of BRS values. Discussion: BRS is severely reduced in obese subjects. BMI, age, and the parasympathetic nervous system activity are the main determinants of BRS. Baroreflex behavior is of clinical relevance because an attenuated BRS represents a negative prognostic factor in cardiovascular diseases, which are common in obesity.     

Comparison of Thermogenic Sympathetic Response to Food Intake between Obese and Non‐obese Young Women

Objective: Sympathetic nervous system abnormality in humans is still a matter of debate. The present study was designed to examine diet‐induced autonomic nervous system activity and metabolic change in obese and non‐obese young women. Research Methods and Procedures: Sixteen age‐ and height‐matched obese and non‐obese young women participated in this study. Sympathovagal activities were assessed by means of our newly developed spectral analysis procedure of heart‐rate variability during the resting condition and after mixed‐food ingestion (480 kcal). Energy expenditure was also measured under these two conditions. Results: There was no significant difference in any of the parameters of the heart‐rate variability between the obese group and control group during the resting condition. In the control group, both absolute values (221.5 ± 54.5 vs. 363.8 ± 43.7 ms², p < 0.05) and relative values (0.23 ± 0.03 to 0.36 ± 0.02, p < 0.05) of a very‐low‐frequency component and global sympathetic nervous system index (1.46 ± 0.19 vs. 3.26 ± 0.61, p < 0.05) were significantly increased after mixed‐food ingestion compared with the values obtained after resting condition. However, no such sympathetic response was found in the obese group. Energy expenditure increased in the two groups after the meal, but the magnitude of the increase above the preprandial resting condition was significantly greater in the control group than in the obese group (11.2 ± 2.3 vs. 6.7 ± 0.8%, p < 0.05). Discussion: Our data suggest that despite identical sympathovagal activities at the resting condition, obese young women may possess a reduced sympathetic response to physiological perturbation such as mixed food intake, which might be related to lowered capacity of thermogenesis and the state of obesity.     

Prevalence of Uncomplicated Obesity in an Italian Obese Population

Objective: The existence of healthy obese subjects has been suggested but not clearly reported. We sought to address the prevalence of uncomplicated obesity and adverse risk factors in a large Italian obese population. Research Methods and Procedures: This was a cross‐sectional study of a population of consecutive Italian obese subjects. We studied 681 obese subjects (514 women and 167 men), with a mean age of 41.1 ± 13.9 years (range, 16 to 77 years), mean BMI of 40.2 ± 7.6 kg/m² (range, 30 to 89.8 kg/m²), and a history of obesity for 20.5 ± 7 years (range, 10.5 to 30 years). Anthropometric, metabolic, cardiac, and obesity‐related risk factors were evaluated. Results: The prevalence of uncomplicated subjects was 27.5%, independent of BMI and duration of obesity. The youngest group of obese subjects showed a higher, but not statistically significantly higher, prevalence of uncomplicated obesity. No statistical difference for the prevalence of impaired fasting glucose, glucose intolerance, high triglycerides, high total cholesterol, low‐density lipoprotein cholesterol, and high‐density lipoprotein cholesterol among BMI categories (from mild to extremely severe obesity degree) was found. Obese subjects with BMI >50 kg/m² showed a higher prevalence of high blood pressure only when they were compared with the group with a BMI of 30 to 35 kg/m² (p < 0.01). Obese subjects with BMI >40 kg/m² showed a higher prevalence of hyperinsulinemia than subjects with BMI 30 to 35 kg/m² (p < 0.01). Discussion: This study shows that a substantial part of an Italian obese population has uncomplicated obesity, and the prevalence of adverse risk factors in this sample is unexpectedly low and partially independent of obesity degree. Uncomplicated obesity could represent a well‐defined clinical entity.     

Sympathovagal Balance,Nighttime Blood Pressure,and QT Intervals in Normotensive Obese Women

Objective : We describe associations among the heart‐rate‐corrected QT (QTc) interval, QTc dispersion (QTc‐d), circadian BP variation, and autonomic function in obese normotensive women and the effect of sustained weight loss. Research Methods and Procedures : In 71 obese (BMI = 37.14 ± 2.6 kg/m²) women, 25 to 44 years of age, circadian BP variations (24‐hour ambulatory BP monitoring), autonomic function (power spectral analysis of RR interval oscillations), and cardiac repolarization times (QTc‐d and QTc interval) were recorded at baseline and after 1 year of a multidisciplinary program of weight reduction. Results : Compared with nonobese age‐matched women (n = 28, BMI = 23 ± 2.0 kg/m²), obese women had higher values of QTc‐d (p < 0.05) and QTc (p < 0.05), an altered sympathovagal balance (ratio of low‐frequency/high‐frequency power, p < 0.01), and a blunted nocturnal drop in BP (p < 0.01). In obese women, QTc‐d and the QTc interval correlated with diastolic nighttime BP (p < 0.01) and sympathovagal balance (p < 0.01). Waist‐to‐hip ratio, free fatty acids, and plasma insulin levels correlated with QT intervals and reduced nocturnal drops in both systolic and diastolic BP and sympathovagal balance (p < 0.01). After 1 year, obese women lost at least 10% of their original weight, which was associated with decrements of QTc‐d (p < 0.02), the QTc interval (p < 0.05), nighttime BP (p < 0.01), and sympathovagal balance (p < 0.02). Discussion : Sustained weight loss is a safe method to ameliorate diastolic nighttime BP drop and sympathetic overactivity, which may reduce the cardiovascular risk in obese women.     

Leptin Responses to Weight Loss in Postmenopausal Women: Relationship to Sex‐Hormone Binding Globulin and Visceral Obesity

Objective: Leptin concentrations increase with obesity and tend to decrease with weight loss. However, there is large variation in the response of serum leptin levels to decreases in body weight. This study examines which endocrine and body composition factors are related to changes in leptin concentrations following weight loss in obese, postmenopausal women. Research Methods and Procedures: Body composition (DXA), visceral obesity (computed tomography), leptin, cortisol, insulin, and sex hormone‐binding globulin (SHBG) concentrations were measured in 54 obese (body mass index [BMI] = 32.0 ± 4.5 kg/m²; mean ± SD), women (60 ± 6 years) before and after a 6‐month hypocaloric diet (250 to 350 kcal/day deficit). Results: Body weight decreased by 5.8 ± 3.4 kg (7.1%) and leptin levels decreased by 6.6 ± 11.9 ng/mL (14.5%) after the 6‐month treatment. Insulin levels decreased 10% (p < 0.05), but mean SHBG and cortisol levels did not change significantly. Relative changes in leptin with weight loss correlated positively with relative changes in body weight (r = 0.50, p < 0.0001), fat mass (r = 0.38, p < 0.01), subcutaneous fat area (r = 0.52, p < 0.0001), and with baseline values of SHBG (r = 0.38, p < 0.01) and baseline intra‐abdominal fat area (r = ?0.27, p < 0.06). Stepwise multiple regression analysis showed that baseline SHBG levels (r² = 0.24, p < 0.01), relative changes in body weight (cumulative r² = 0.40, p < 0.05), and baseline intra‐abdominal fat area (cumulative r² = 0.48, p < 0.05) were the only independent predictors of the relative change in leptin, accounting for 48% of the variance. Discussion: These results suggest that obese, postmenopausal women with a lower initial SHBG and more visceral obesity have a greater decrease in leptin with weight loss, independent of the amount of weight lost.     

Effects of Dinner Composition on Postprandial Macronutrient Oxidation in Prepubertal Girls

Objective: To see whether a fat‐rich (50%) evening meal promoted fat oxidation and a different spontaneous food intake on the following day at breakfast than a meal with a lower fat content (20%) in 10 prepubertal obese girls. Research Methods and Procedures: The postabsorptive and postprandial (10.5 hours) energy expenditure after a low‐fat (LF) (20% fat, 68% carbohydrate, 12% protein) and an isocaloric (2.1 MJ) and isoproteic high‐fat (HF; 50% fat, 38% carbohydrate, 12% protein) meal were measured by in direct calorimetry. Results: Fat oxidation was not significantly different after the two meals [LF, 31 ± 9 vs. HF, 35 ± 9 g/10.5 hours, p = not significant (NS)]. The girls oxidized 1.8 ± 0.9 times more fat than that ingested (11.1 grams) with the LF meal vs. 0.3 ± 0.3 times more fat than that ingested (27.1 grams) with the HF meal (p < 0.001). Carbohydrate oxidation was significantly higher after an LF than an HF meal (39 ± 12 vs. 29 ± 9 g/10.5 hours, p < 0, 05). At breakfast, the girls spontaneously ingested a similar amount of energy (1.5 ± 0.7 vs. 1.5 ± 0.6 MJ, p = NS) and macronutrient proportions (fat, 23% vs. 26%, p = NS; protein, 9% vs. 10%; carbohydrate, 68% vs. 64%,) independently of their having eaten an HF or an LF dinner. Discussion: An HF dinner did not stimulate fat oxidation, and no compensatory effect in spontaneous food intake was observed during breakfast the following morning. Cumulated total fat oxidation after dinner was higher than total fat ingested at dinner, but a much larger negative fat balance was observed after the LF meal. Spontaneous energy and nutrient intakes at breakfast were similar after LF and HF isocaloric, isoproteic dinners. This study points out the lack of sensitivity of short‐term fat balance to subsequently readjust fat intake and emphasizes the importance of an LF meal to avoid transient positive fat imbalance.     

Insulin Sensitivity Determines the Effectiveness of Dietary Macronutrient Composition on Weight Loss in Obese Women

Objective: To determine whether macronutrient composition of a hypocaloric diet can enhance its effectiveness and whether insulin sensitivity (Si) affects the response to hypocaloric diets. Research Methods and Procedures: Obese nondiabetic insulin‐sensitive (fasting insulin < 10 μU/mL; n = 12) and obese nondiabetic insulin‐resistant (fasting insulin > 15 μU/mL; n = 9) women (23 to 53 years old) were randomized to either a high carbohydrate (CHO) (HC)/low fat (LF) (60% CHO, 20% fat) or low CHO (LC)/high fat (HF) (40% CHO, 40% fat) hypocaloric diet. Primary outcome measures after a 16‐week dietary intervention were: changes in body weight (BW), Si, resting metabolic rate, and fasting lipids. Results: Insulin‐sensitive women on the HC/LF diet lost 13.5 ± 1.2% (p < 0.001) of their initial BW, whereas those on the LC/HF diet lost 6.8 ± 1.2% (p < 0.001; p < 0.002 between the groups). In contrast, among the insulin‐resistant women, those on the LC/HF diet lost 13.4 ± 1.3% (p < 0.001) of their initial BW as compared with 8.5 ± 1.4% (p < 0.001) lost by those on the HC/LF diet (p < 0.04 between two groups). These differences could not be explained by changes in resting metabolic rate, activity, or intake. Overall, changes in Si were associated with the degree of weight loss (r = ?0.57, p < 0.05). Discussion: The state of Si determines the effectiveness of macronutrient composition of hypocaloric diets in obese women. For maximal benefit, the macronutrient composition of a hypocaloric diet may need to be adjusted to correspond to the state of Si.     

Raised Interleukin‐6 Levels in Obese Patients

Objective: Obese patients demonstrate a variety of biochemical, metabolic, and pulmonary abnormalities. Inflammatory mediators such as tumor necrosis factor‐α and interleukin‐6 (IL‐6) may have a direct effect on glucose and lipid metabolism. Hypoxemia in itself induces release of IL‐6. The aim of this study was to examine the relationship between IL‐6 levels in healthy volunteers (control group) and three different groups of obese patients: patients without obstructive sleep apnea syndrome (OSAS), patients with OSAS, and patients with obesity hypoventilation syndrome (OHS) (daytime baseline oxygen saturation of <93%). Research Methods and Procedures: We measured serum IL‐6 levels in 25 obese patients (body mass index of >35 kg/m²) and 12 healthy women. Results: The results demonstrate statistically significant differences in serum IL‐6 levels between the control group (1.28 ± 0.85 pg/mL) and obese patients without OSAS (7.69 ± 5.06 pg/mL, p < 0.05) and with OSAS (5.58 ± 0.37 pg/mL, p < 0.0005). In the patients with OHS, IL‐6 concentrations were highest (43.13 ± 24.27 pg/mL). Discussion: We conclude that serum IL‐6 is increased in obese patients. The highest IL‐6 levels were found in the patients with OHS.     

Liver Volume and Visceral Obesity in Women with Hepatic Steatosis Undergoing Gastric Banding

Objective: To investigate the relationships between visceral obesity and hepatic steatosis in obese patients undergoing adjustable silicone gastric banding with the LAP‐BAND. Research Methods and Procedures: Six premenopausal, morbidly obese women with an ultrasonographic diagnosis of liver steatosis were evaluated before surgery and 8 and 24 weeks after surgery. Liver volume and body fat distribution were simultaneously analyzed by total‐body multislices magnetic resonance imaging. Results: Before surgery, the only variable found to be correlated with liver volume was visceral adipose tissue volume (r = 0.91; p < 0.01). Weight loss was 9.9 ± 3.8 kg in the period from 0 to 8 weeks (p < 0.01) and 7.1 ± 4.9 kg in the the period from 8 to 24 weeks (p < 0.05). Total fat showed a statistically significant reduction of 6.2 ± 4.0 liters in the 0‐ to 8‐week period and a further significant reduction of 7.7 ± 3.9 liters in the 8‐ to 24‐week period. Visceral adipose tissue showed a statistically significant reduction of 1.0 ± 0.9 liters in the 0‐ to 8‐week period (p < 0.05) but only a further, not significant reduction of 0.6 ± 0.7 liters in the 8‐ to 24‐week period. The relative reduction of visceral fat in the 0‐to 8‐week period was higher than the relative reduction of total fat. Liver volume also showed a statistically significant reduction of 0.24 ± 0.26 liters in the first phase of weight loss (p < 0.05), corresponding to a relative reduction of 12.3 ± 10.6%. During the 8‐ to 24‐week period, liver volume was substantially stable. Discussion: Hepatomegaly was associated with visceral obesity in morbidly obese women with liver steatosis. In the phase of rapid weight loss after gastric surgery, a preferential mobilization of visceral fat, compared with total adipose tissue, occurred. This preferential visceral fat loss was associated with a significant reduction in liver volume.     

Adapted Changes in Left Ventricular Structure and Function in Severe Uncomplicated Obesity

Objective: A massive amount of fat tissue, as that observed in obese subjects with BMI over 50 kg/m², could affect cardiac morphology and performance, but few data on this issue are available. We sought to evaluate cardiac structure and function in uncomplicated severely obese subjects. Research Methods and Procedures: We studied 55 uncomplicated severely obese patients, 40 women, 15 men, mean age 35.5 ± 10.2 years, BMI 51.2 ± 8.8 kg/m², range 43 to 81 kg/m², with a history of fat excess of at least 10 years, and 55 age‐matched normal‐weight subjects (40 women, 15 men, mean BMI 23.8 ± 1.2 kg/m²) as a control group. Each subject underwent an echocardiogram to evaluate left ventricular (LV) mass and geometry and systolic and diastolic function. Results: Severely obese subjects showed greater LV mass and indexed LV mass than normal‐weight subjects (p < 0.01 for all parameters). Nevertheless, LV mass was appropriate for sex, height^2.7, and stroke work in most (77%) uncomplicated severely obese subjects. In addition, no significant difference in LV mass indices and LV mass appropriateness between obese subjects with BMI ≥ 50 kg/m² and those with BMI ≤ 50 kg/m² was found. Obese subjects also showed higher ejection fraction and midwall shortening than normal‐weight subjects (p = 0.05 and p < 0.01, respectively), suggesting a hyperdynamic systolic function. No significant difference in systolic performance between obese subjects with BMI ≥ 50 kg/m² and those with BMI ≤ 50 kg/m² was seen. Discussion: Our data show that uncomplicated severe obesity, despite the massive fat tissue amount, is associated largely with adapted and appropriate changes in cardiac structure and function.     

The Relationship of Health Outcomes to Improvement in BMI in Children and Adolescents

Objective: To evaluate the clinical outcomes of patients participating in an outpatient program for managing childhood and adolescent obesity. Research Methods and Procedures: Based on a retrospective chart review, 394 physician‐referred obese youth (BMI > 95th percentile), 5 to 19 years of age, were treated in an interdisciplinary, family‐centered, behavioral weight management program in a hospital‐based outpatient setting. Treatment included group exercise, parent education, and behavioral intervention therapies to improve diet and physical activity. Results: A total of 177 (45%) completed the initial phase of treatment (mean duration = 5.6 months). For the completion group, there were significant improvements (all p < 0.001) in weight (?2.0 ± 4.9 kg), BMI (?1.7 ± 1.9 kg/m²), and BMI z score (?0.15 ± 0.15), without interfering with growth (height, 2.2 ± 1.3 cm; p < 0.001). Significant improvement was also found for blood pressure, total cholesterol, low‐density lipoprotein (LDL)‐cholesterol, triglycerides, insulin, and aerobic fitness. At onset of treatment, 134 (84%) patients had abnormal fasting insulin concentration, 88 (50%) had abnormal total cholesterol, 14 (8%) had abnormal diastolic blood pressure, and 69 (40%) had abnormal LDL‐cholesterol. At the end of treatment, a significant proportion of patients with baseline abnormal blood pressure, total cholesterol, and LDL‐cholesterol had normal values (p < 0.001). A decrease in BMI z score was associated with significant improvements in insulin and lipid values (all p < 0.05). Discussion: We have demonstrated that a modest decrease in BMI in an ongoing clinical pediatric weight management program is accompanied by significant improvements in related health measures. These results may be helpful in counseling families with overweight children and adolescents.     

Obesity Affects Myocardial Vasoreactivity and Coronary Flow Response to Insulin

Objective: Obesity is associated with increased risk for cardiovascular diseases and peripheral endothelial dysfunction. We examined whether myocardial vasoreactivity and coronary‐flow response to insulin stimulation are altered in obesity. Research Methods and Procedures: Myocardial blood flow was quantitated in 10 obese men (body mass index, 33.6 ± 1.9 kg/m²) and 10 healthy matched non‐obese men (body mass index, 24.2 ± 1.9 kg/m²), using positron emission tomography and oxygen‐15‐labeled water. The measurements were performed basally and during adenosine infusion (140 μg/kg per minute), with or without simultaneous physiological (1 mU/kg per minute) and supraphysiological (5 mU/kg per minute) hyperinsulinemia. Results: Basal myocardial blood flow was not significantly different between obese and non‐obese subjects. Adenosine‐stimulated flow was blunted in obese (3.2 ± 0.6 mL/g per minute) when compared with non‐obese subjects (4.0 ± 1.1 mL/g per minute, p < 0.05). Simultaneous physiological hyperinsulinemia increased adenosine‐stimulated myocardial flow significantly in both groups (to 4.03 ± 1.24 and 4.85 ± 1.04 mL/g per minute in obese and non‐obese men, respectively; p < 0.05 vs. adenosine). Supraphysiological hyperinsulinemia further enhanced the adenosine‐stimulated flow in non‐obese subjects (to 5.56 ± 0.98 mL/g per minute; p < 0.05) but not in obese subjects. Discussion: Young obese, healthy men have reduced myocardial vasoreactivity, which may represent an early precursor of future coronary artery disease. Additionally, insulin‐induced enhancement of myocardial blood flow is blunted in obesity. Thus, endothelial dysfunction seems to also characterize myocardial vasculature of obese subjects.     

Weight Loss Reduces Tissue Factor in Morbidly Obese Patients

Objective: To investigate the tissue factor (TF) pathway in clinical obesity and associated metabolic syndrome. Research Methods and Procedures: Thirty‐seven morbidly obese patients (4 men; BMI, 48 ± 7 kg/m²; range, 42 to 53 kg/m²), undergoing elective gastroplasty for the induction of weight loss, were examined for hemostatic, metabolic, and inflammatory parameters at baseline and 14 ± 5 months postoperatively. Results: Weight loss significantly reduced circulating plasma TF (314 ± 181 vs. 235 ± 113 pg/mL, p = 0.04), coagulation factor VII (130 ± 22% vs. 113 ± 19%, p = 0.023), and prothrombin fragment F1.2 (2.4 ± 3.4 vs. 1.14 ± 1.1 nM, p = 0.04) and normalized glucose metabolism in 50% of obese patients preoperatively classified as diabetic or of impaired glucose tolerance. The postoperative decrease in plasma TF correlated with the decrease of F1.2 (r = 0.56; p = 0.005), a marker of in vivo thrombin formation. In subgroup analysis stratified by preoperative glucose tolerance, baseline circulating TF (402.6 ± 141.6 vs. 176.2 ± 58.2, p < 0.001) and TF decrease after gastroplasty (ΔTF: 164.7 ± 51.4 vs. ?81 ± 31 pg/mL, p = 0.02) were significantly higher in obese patients with impaired glucose tolerance than in patients with normal glucose tolerance. Discussion: Procoagulant TF is significantly reduced with weight loss and may contribute to a reduction in cardiovascular risk associated with obesity.     

Intentional Weight Loss Reduces Mortality Rate in a Rodent Model of Dietary Obesity

Objective: We used a rodent model of dietary obesity to evaluate effects of caloric restriction‐induced weight loss on mortality rate. Research Measures and Procedures: In a randomized parallel‐groups design, 312 outbred Sprague‐Dawley rats (one‐half males) were assigned at age 10 weeks to one of three diets: low fat (LF; 18.7% calories as fat) with caloric intake adjusted to maintain body weight 10% below that for ad libitum (AL)‐fed rat food, high fat (HF; 45% calories as fat) fed at the same level, or HF fed AL. At age 46 weeks, the lightest one‐third of the AL group was discarded to ensure a more obese group; the remaining animals were randomly assigned to one of three diets: HF‐AL, HF with energy restricted to produce body weights of animals restricted on the HF diet throughout life, or LF with energy restricted to produce the body weights of animals restricted on the LF diet throughout life. Life span, body weight, and leptin levels were measured. Results: Animals restricted throughout life lived the longest (p < 0.001). Life span was not different among animals that had been obese and then lost weight and animals that had been nonobese throughout life (p = 0.18). Animals that were obese and lost weight lived substantially longer than animals that remained obese throughout life (p = 0.002). Diet composition had no effect on life span (p = 0.52). Discussion: Weight loss after the onset of obesity during adulthood leads to a substantial increase in longevity in rats.     

Effect of Gastric Banding on Aminoterminal Pro‐brain Natriuretic Peptide in the Morbidly Obese

Objective: Aminoterminal pro‐brain natriuretic peptide (NT‐proBNP), like brain natriuretic peptide, might have diagnostic utility in detecting left ventricular hypertrophy and/or left ventricular dysfunction. The aim of the study was to investigate the relationship between morbid obesity and NT‐proBNP and the effect of weight reduction on this parameter. Research Methods and Procedures: A total of 34 morbidly obese patients underwent laparoscopic adjustable gastric banding (LAGB). NT‐proBNP levels were measured before and 12 months after the surgery. Results: Metabolic features and systolic and diastolic blood pressure were significantly decreased (p < 0.00001 for both) after a cumulative weight loss of 19.55 kg 1 year after LAGB. NT‐proBNP concentration was significantly higher in morbidly obese patients before LAGB than in normal‐weight control subjects (341.15 ± 127.78 fmol/mL vs. 161.68 ± 75.78 fmol/mL; p < 0.00001). After bariatric surgery, NT‐proBNP concentration decreased significantly from 341.15 ± 127.78 fmol/mL to 204.87 ± 59.84 fmol/mL (p < 0.00, 001) and remained statistically significantly elevated (204.88 ± 59.84 fmol/mL vs. 161.68 ± 75.78 fmol/mL; p = 0.04) compared with normal‐weight subjects. Discussion: This investigation demonstrates higher levels of NT‐proBNP in morbidly obese subjects and a significant decrease during weight loss after laparoscopic adjustable gastric banding. In obesity, NT‐proBNP might be useful as a routine screening method for identifying left ventricular hypertrophy and/or left ventricular dysfunction.     

Obesity Prevention in Preschool Native‐American Children: A Pilot Study Using Home Visiting

Objective : To determine whether maternal participation in an obesity prevention plus parenting support (OPPS) intervention would reduce the prevalence of obesity in high‐risk Native‐American children when compared with a parenting support (PS)‐only intervention. Research Methods and Procedures : Forty‐three mother/child pairs were recruited to participate. Mothers were 26.5 ± 5 years old with a mean BMI of 29.9 ± 3 kg/m². Children (23 males) were 22 ± 8 months old with mean weight‐for‐height z (WHZ) scores of 0.73 ± 1.4. Mothers were randomly assigned to a 16‐week OPPS intervention or PS alone. The intervention was delivered one‐on‐one in homes by an indigenous peer educator. Baseline and week 16 assessments included weight and height (WHZ score and weight‐for‐height percentile for children), dietary intake (3‐day food records), physical activity (measured by accelerometers), parental feeding style (Child Feeding Questionnaire), and maternal outcome expectations, self‐efficacy, and intention to change diet and exercise behaviors. Results : Changes in WHZ scores showed a trend toward significance, with WHZ scores decreasing in the PS condition and increasing among the OPPS group (?0.27 ± 1.1 vs. 0.31 ± 1.1, p = 0.06). Children in the OPPS condition also significantly decreased energy intake (?316 ± 835 kcal/d vs. 197 ± 608 kcal/d, p < 0.05). Scores on the restriction subscale of the Child Feeding Questionnaire decreased significantly in the OPPS condition (?0.22± 0.42 vs. 0.08± 0.63, p < 0.05), indicating that mothers in the OPPS group were engaging in less restrictive child feeding practices over time. Discussion : A home‐visiting program focused on changing lifestyle behaviors and improving parenting skills showed promise for obesity prevention in high‐risk Native‐American children.     

High Serum Leptin Is Associated with Attenuated Coronary Vasoreactivity

Objective: Hyperleptinemia, a hallmark of obesity, appears to be a risk factor for coronary artery disease. However, although leptin is a vasoactive hormone, no studies addressing leptin's effect on coronary perfusion have been performed. We examined the association between circulating leptin concentration and coronary vasoreactivity in young obese and nonobese males. Research Methods and Procedures: Myocardial blood flow was quantitated in 10 obese men (age 31 ± 7 years, BMI 34 ± 2 kg/m²) and 10 healthy matched nonobese men (age 33 ± 8 years, BMI 24 ± 2 kg/m²) using positron emission tomography and O‐15‐water. The measurements were performed basally and during adenosine infusion (140 μg/kg per minute). Results: Serum leptin was significantly higher in obese than nonobese subjects (10.3 ± 5.6 vs. 4.3 ± 2.5 ng/mL, p < 0.01). Basal myocardial blood flow was not significantly different between obese and nonobese subjects. Adenosine‐stimulated flow was blunted in obese (3.2 ± 0.6 mL/g per minute) when compared with nonobese subjects (4.0 ± 1.1 mL/g per minute, p < 0.05). Serum leptin concentration was inversely associated with adenosine‐stimulated flow in study subjects (r = ?0.50, p < 0.05). This association was no longer observed after adjustment for obesity and/or hyperinsulinemia. Discussion: Hyperleptinemia and reduced coronary vasoreactivity occur concomitantly in young obese but otherwise healthy men. Moreover, the adenosine‐stimulated myocardial flow is inversely related to prevailing concentration of serum leptin. Although this relationship appears to be explained by obesity and/or hyperinsulinemia, leptin might have a role in regulation of myocardial blood supply.     

Total and Regional Fat and Serum Cardiovascular Disease Risk Factors in Lean and Obese Children and Adolescents

Objective: This study was conducted to evaluate the association of total and central adiposity with serum cardiovascular disease (CVD) risk factors in lean and obese Portuguese children and adolescents. Research Methods and Procedures: A total of 87 girls (13.2 ± 1.6 years old, 29.9 ± 6.4% body fat [mean ± SD]) and 72 boys (13.2 ± 1.6 years old, 20.8 ± 9.9% body fat) volunteered for the study. Whole‐body composition and fat distribution, from DXA and anthropometry, and serum lipids, lipoproteins, and apolipoproteins were evaluated. Results: The sum of three trunk skinfolds (STS) was highly correlated with total trunk fat mass measured by DXA (p < 0.001). Body mass index, DXA‐measured percentage of body fat, trunk fat mass, STS, and the waist‐to‐height ratio were generally found to be associated with triacylglycerol, the ratio of total cholesterol (TC) to high density lipoprotein‐cholesterol (HDL‐C), low density lipoprotein‐cholesterol (LDL‐C), and apolipoprotein B levels, (significant age‐adjusted r between 0.16 and 0.27, p < 0.05). Body mass index, STS, and the waist circumference were also associated with HDL‐C (p < 0.05), whereas no body composition variable significantly correlated with TC or apolipoproteins A‐I. The STS was significantly correlated with HDL‐C (p < 0.01), TC/HDL‐C (p < 0.05), and apolipoproteins A‐I (p < 0.05) independently of whole‐body fatness. Obese subjects (n = 73) had higher TC, LDL‐C, TC/HDL‐C, and apolipoprotein B than did non‐obese subjects (n = 86), and significant associations between central adiposity and some lipid variables (triacylglycerol and HDL‐C) were found in obese children and adolescents that were not present in leaner individuals. Discussion: DXA‐ and anthropometry‐based whole‐body and central fat measures are associated with serum CVD risk factors in Portuguese boys and girls. Obese children and adolescents have a poorer lipid profile than do their leaner counterparts. Trunk skinfolds, which are easy to obtain even in large samples, predict CVD risk factors to the same extent as DXA‐based variables, in some cases, independently of total fatness.     

Adiponectin Levels during Low‐ and High‐Fat Eucaloric Diets in Lean and Obese Women

Objective: Adiponectin influences insulin sensitivity (S_I) and fat oxidation. Little is known about changes in adiponectin with changes in the fat content of eucaloric diets. We hypothesized that dietary fat content may influence adiponectin according to an individual's S_I. Research Methods and Procedures: We measured changes in adiponectin, insulin, glucose, and leptin in response to high‐fat (HF) and low‐fat (LF) eucaloric diets in lean (n = 10) and obese (n = 11) subjects. Obese subjects were further subdivided in relation to a priori S_I. Results: We found significantly higher insulin, glucose, and leptin and lower adiponectin in obese vs. lean subjects during both HF and LF. The mean group values of these measurements, including adiponectin (lean, HF 21.9 ± 9.8; LF, 20.8 ± 6.6; obese, HF 10.0 ± 3.3; LF, 9.5 ± 2.3 ng/mL; mean ± SD), did not significantly change between HF and LF diets. However, within the obese group, the insulin‐sensitive subjects had significantly higher adiponectin during HF than did the insulin‐resistant subjects. Additionally, the change in adiponectin from LF to HF diet correlated positively with the obese subjects’ baseline S_I. Discussion: Although in lean and obese women, group mean values for adiponectin did not change significantly with a change in fat content of a eucaloric diet, a priori measured S_I in obese subjects predicted an increase in adiponectin during the HF diet; this may be a mechanism that preserves S_I in an already obese group.