Search

The objective of this study was to investigate the effect of long-term exercise training on concentrations of five hormones related to appetite and insulin resistance in overweight adolescents. In addition, we were interested in the relationships of these hormones with each other and with anthropometric and/or cardiovascular disease marker changes. Participants were ≥ the 85th percentile for BMI for age and sex and participated in an 8-month supervised aerobic training program. Anthropometrics, cardiovascular fitness assessment, and fasting blood samples were taken pre- and post-training. Glucose, insulin, total cholesterol (TC), high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triglycerides, leptin, active ghrelin, total peptide YY (PYY), adiponectin, and resistin concentrations were measured. The participants increased their time to exhaustion on an incremental treadmill test and decreased both percent body fat and blood triglyceride concentrations. Total PYY concentration increased and resistin concentration decreased after long-term exercise training, which are favorable outcomes. Leptin concentrations were related to weight, percent body fat, waist circumference, and triglyceride concentrations pre- and post-training. The changes in resistin concentrations were related to the changes in triglyceride concentrations. We conclude that long-term exercise training has beneficial effects for overweight adolescents with respect to PYY and resistin, hormones related to appetite and insulin sensitivity.Obesity (2009) 17 6, 1189–1195. doi:10.1038/oby.2009.11 [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to determine whether fasting plasma leptin concentration was altered with an increase in training volume in competitive male and female athletes., Methods: Intercollegiate male (N = 9) and female (N = 12) swimmers were examined during the preseason and at two times during the mid-season (mid-season 1 and mid-season 2) when training volume was relatively high (33,000 m.wk(-1)). Body composition (hydrostatic weighing), energy intake and expenditure, and fasting plasma leptin concentration were measured., Results: In the women, there was a significant (P < 0.05) decline in fat mass (2 kg) with the increase in training volume, which was not accompanied by a reduction in fasting leptin (12.8 +/- 1.5 vs 11.0 +/- 1.2 vs 11.0 +/- 1.5 ng.mL(-1) for preseason, mid-season 1, and mid-season 2, respectively). In the men, there were no significant changes in body composition, body mass, or fasting leptin (4.4 +/- 0.8 vs 4.3 +/- 0.8 vs 4.6 +/- 0.8 ng.mL(-1), respectively)., Conclusion: These findings suggest 1) plasma leptin is not sensitive to an increase in training volume and 2) leptin may not be indicative of changes in fat mass with an increase in training volume in female athletes. These data suggest that leptin may not be useful in monitoring relative training stress in athletes.

Leptin, the product of the ob gene, is an adipose tissue-derived hormone that appears to regulate both satiety and thermogenesis. In the present report, we have reexamined the relationship between circulating leptin concentration and body fat in humans using a more valid measure of adiposity (hydrodensitometry) and have extended these observations to examine the influence of regional body fat distribution and cardiorespiratory fitness. Fasting serum leptin concentration was 6.9 +/- 0.3 ng.ml-1 in males (N = 333) and 15.2 +/- 1.3 ng.ml-1 in females (N = 63). Interestingly, total fat mass did not differ between groups (males 20.5 +/- 0.5 kg; females 20.4 +/- 1.5 kg), suggesting that females have higher leptin levels per unit fat mass. In a multiple regression model, fat mass was the best predictor of serum leptin concentration in males, accounting for 51% of the variance in leptin concentration. In females, percentage body fat was the best predictor of leptin, accounting for 49% of the variance. In both groups, the relationship between leptin and adiposity remained significant after adjusting for age, maximal treadmill time, waist circumference, and fasting insulin concentration. These observations support previous conclusions that circulating leptin is primarily a function of adiposity and demonstrate for the first time that this relationship is independent of fat distribution or cardiorespiratory fitness. The data also suggest that there is a gender dichotomy in the relationship between leptin and body fat mass in humans.

Objective: To determine which anthropometric methods of assessing body fat distribution are the most predictive of the insulin resistance of aging., Design: Commonly used indices of regional adiposity were correlated with whole-body insulin sensitivity in 55 men and 29 women (age range 18-80 years)., Measurements: Insulin sensitivity (SI, minimal model), waist and hip girths, waist-to-hip ratios, conicity index, skinfolds, body fat percentage, maximal oxygen consumption., Results: There was a wide disparity in the strength of relationships between commonly used anthropometric indices of fat distribution and whole-body insulin sensitivity. In both sexes minimal waist girth, however, was the primary variable in multivariate regression analysis, accounting for approximately 37% of the variance in SI., Conclusion: These findings indicate that anthropometric measures of regional adiposity are not interchangeable and/or equivalent when attempting to discern relationships between body fat distribution, insulin sensitivity, and aging.

The purpose of the present study was to determine whether absolute and relative measurements of regional adiposity differ in their responses to exercise intervention and which measures are most predictive of changes in plasma lipids, insulin sensitivity and adiposity. Thirteen middle-aged men (BMI 30.4 +/- 1.5 kg/m2, age 47.2 +/- 1.5 years, mean +/- s.e.) were examined before and after 14 weeks of endurance-oriented physical activity (3-4 days/week, 30-45 min/day). Significant (P < 0.05) decreases in the absolute measures of chest, waist and hip girths and sagittal diameter were evident. The waist-to-hip ratios (WHR) of umbilicus/maximal hip and minimal waist/maximal hip decreased significantly (P < 0.05). However, the WHRs of umbilicus/anterior superior iliac spine and umbilicus/greater trochanters did not change due to parallel decreases in waist and hip girths. Trunk and extremity skinfolds decreased significantly (P < 0.05); however, trunk/extremity skinfold ratios were virtually unaltered. The training programme significantly (P < 0.05) increased insulin sensitivity (60%) and HDL (8%), and reduced triglyceride (25%) and total cholesterol/HDL (8%). Changes in these variables were related to changes in sagittal diameter and waist girth. These data indicate different responses to physical activity between measurements of regional adiposity, and emphasize the need for considering absolute central girths such as waist circumference and sagittal diameter when assessing fat topography and cardiovascular risk.

The purpose of the present study was to determine the effects of exercise training on the chemical composition of plasma low-density lipoprotein (LDL). Thirteen men (mean age +/- SE, 47.2 +/- 1.5 years) were examined before and after 14 weeks of endurance-oriented exercise training (3 to 4 d/wk, 30 to 45 min/d). Although calculated plasma LDL concentrations remained unaltered (3.49 +/- 0.24 versus 3.65 +/- 0.23 mmol/L), changes in the chemical composition of LDL (increased LDL free cholesterol, cholesterol ester, and phospholipid content) were associated with a reduction in adiposity, umbilical girth, and basal plasma insulin and glucose concentration with training intervention. Increases in LDL molecular weight and particle diameter were associated with a reduction in fat mass, plasma triglyceride concentration, and basal plasma glucose concentration with physical activity. The LDL lipid-to-protein ratio also increased (P < .01) with training by 7%, primarily due to an increase in LDL free cholesterol content (P < .01). These findings indicate the formation of LDL particles that are more cholesterol enriched and protein poor with exercise training, which provides additional evidence for the cardioprotective effect of long-term physical activity.

It was hypothesized that athletic massage administered 2 hours after eccentric exercise would disrupt an initial crucial event in acute inflammation, the accumulation of neutrophils. This would result in a diminished inflammatory response and a concomitant reduction in delayed onset muscle soreness (DOMS) and serum creatine kinase (CK). Untrained males were randomly assigned to a massage (N = 7) or control (N = 7) group. All performed five sets of isokinetic eccentric exercise of the elbow flexors and extensors. Two hours after exercise, massage subjects received a 30-minute athletic massage; control subjects rested. Delayed onset muscle soreness and CK were assessed before exercise and at 8, 24, 48, 72, 96, and 120 hours after exercise. Circulating neutrophils were assessed before and immediately after exercise, and at 30-minute intervals for 8 hours; cortisol was assessed before and immediately after exercise, and at 30-minute intervals for 8 hours; cortisol was assessed at similar times. A trend analysis revealed a significant (p < 0.05) treatment by time interaction effect for 1) DOMS, with the massage group reporting reduced levels; 2) CK, with the massage group displaying reduced levels; 3) neutrophils, with the massage group displaying a prolonged elevation; and 4) cortisol, with the massage group showing a diminished diurnal reduction. The results of this study suggest that sports massage will reduce DOMS and CK when administered 2 hours after the termination of eccentric exercise. This may be due to a reduced emigration of neutrophils and/or higher levels of serum cortisol.

The purpose of this study was to compare the accuracy of four methods to assess body composition of women. Seventy-seven Caucasian women [mean (+/- SD) age: 31.8 +/- 8.6 years; mass: 59.5 +/- 9.1 kg; stature: 162.4 +/- 6.9 cm; Quetelet Index: 22.5 +/- 3.1 kg/m2] were tested for percent body fat (%BF) with hydrostatic weighing (HW), near-infrared spectrophotometry (NIR), bioelectrical impedance analysis (BIA), and seven-site skinfolds (7-SFs). Compared to %BF with HW (24.9 +/- 6.5%), an analysis of variance revealed no mean differences (P > or = 0.05) among %BF with NIR (26.0 +/- 5.5%), BIA (25.7 +/- 5.8%) and 7-SFs (24.0 +/- 6.0%). The correlations between %BF with HW and NIR, BIA and 7-SF were r = 0.47, r = 0.77, and r = 0.79, respectively (P < or = 0.05), and prediction errors (SEE) were 5.8%, 4.2%, and 4.1%. Comparisons of %BF obtained from machine readings versus those computed from the manufacturer's equation indicated significant differences for the BIA (machine 25.7%, equation 27.8%) and NIR (machine 26.0%, equation 21.5%) methods. We concluded that although the mean %BF differences were small among the four methods, the large SEE values may allow the use of BIA and 7-SFs but not NIR. Inaccuracies of machine readings versus equation-computed %BF indicate that BIA and NIR variables and/or constants in the equations supplied are not identical to those used in machine-generated calculations.

The purpose of this study was to determine if static and ballistic stretching would induce significant amounts of delayed onset muscle soreness (DOMS) and increases in creatine kinase (CK). Twenty males were randomly assigned to a static (STATIC) or ballistic stretching (BALLISTIC) group. All performed three sets of 17 stretches during a 90-min period, the only group difference being that STATIC remained stationary during each 60-s stretch while BALLISTIC performed bouncing movements. Subjective ratings of DOMS (scale: 1-10) and serum CK levels were assessed before and every 24 hours post stretching, for 5 days. A repeated measures ANOVA revealed a significant main effect due to time (p < 0.05), with peak soreness occurring at 24 hours after (M = 2.8 +/- 1.6). Surprisingly, a group effect (p < .05) demonstrated that DOMS was significantly greater for STATIC than for BALLISTIC. At 24 hours there was a 62% (p < .05) increase in CK for combined groups. These findings indicate that similar bouts of static and ballistic stretching induce significant increases in DOMS and CK in subjects unaccustomed to such exercise. Furthermore, static stretching induced significantly more DOMS than did ballistic.

Percent body fat (%BF) was assessed in 171 men with underwater weighing (UWW), seven-site skinfolds (7 SF), and near-infrared spectrophotometry (NIR). NIR was determined at eight sites, including biceps, triceps, axilla, chest, abdomen, suprailium, subscapula and thigh. Analysis of variance and Dunnett's post-hoc procedure revealed that NIR significantly (P less than 0.05) underpredicted %BF when using the biceps (12.9%), chest (11.3%), abdomen (10.2%), subscapula (11.3%) and thigh (9.9%) sites compared to the criterion %BF measured with UWW (13.4% +/- SD = 6.49). %BF with 7 SF was only 0.3% higher than %BF with UWW (r = 0.94, standard error of estimate = 2.9%). Correlation coefficients between SF thickness and NIR optical density readings at 940 nm (OD1) and 950 nm (OD2) wavelengths ranged from r = -0.30 (subscapula) to r = -0.67 (biceps) for OD1 and r = -0.39 (axilla) to r = -0.68 (biceps) for OD2. Multiple linear regression showed that the OD readings were not significant predictors of UWW %BF when using body mass, stature, activity level, and frame size as predictors, except for the OD2 reading at the biceps site. Stepwise regression revealed that NIR OD readings did not predict additional variance in %BF beyond mass, stature, activity level, frame size, or 7 SF. It was concluded that 7 SF are better predictors of %BF than NIR, and that NIR at multiple sites is inconsistent in assessing body composition.

Many cross-sectional studies have demonstrated the influences of fitness level or the regional distribution of fat on lipid and carbohydrate metabolism; however, the relative contribution of these two variables in the same subjects has not been extensively examined. The purpose of this study was to determine the impact of regional adiposity on plasma lipids and carbohydrate metabolism in middle- to older-aged men with a wide range of fitness levels. Forty-six sedentary and exercise-trained men (age [mean +/- SE], 52.8 +/- 0.88 years) were included in this study. Fitness level was assessed by (a) time to exhaustion, and (2) maximal oxygen uptake achieved during an incremental treadmill test. Plasma lipid levels were determined in the basal, fasting state. Carbohydrate metabolism was evaluated by the glucose and insulin responses (total glucose and insulin areas under the curve, insulin sensitivity index [ISI]) to a 75-g, 2-hour oral glucose tolerance test (OGTT). Abdomen to hip ratio (AHR) was used as the index of regional adiposity. Multiple regression analysis indicated that fitness level and the percentage of body fat were significant predictors (approximately 56% of total variance) for total insulin area under the curve and the ISI. A comparison between the sedentary and trained subjects showed that training resulted in an improved ISI at an equal AHR. Fitness level was also the only significant multiple regression predictor for high-density lipoprotein (HDL)-cholesterol (25% of total variance) and accounted for the greatest amount of variance in triglyceride levels (34%), although AHR was also a significant predictor (6%).(ABSTRACT TRUNCATED AT 250 WORDS)

The purpose of this study was to determine which method of measuring waist to hip ratio (WHR) was the most effective in assessing decrements associated with an abdominal fat distribution in 46 non-obese, middle to older aged men (mean +/- s.e., age 52.8 +/- 0.88 years; body fat 19.7 +/- 0.72 percent). Circumferences were obtained at the following sites and WHR calculated (waist circumference/hip circumference): (1) minimal waist/maximal hip; (2) level of umbilicus/maximal hip; (3) level of umbilicus/level of greater trochanters; (4) level of umbilicus/level of superior iliac spine; and (5) level of 1/3 of the distance between the xiphiod process and umbilicus/level 4 cm below the superior iliac spine. Significant (P less than 0.05) associations were observed for measurement methods 1, 2 and 3 with indices of lipid and carbohydrate metabolism, body composition, and fitness level. Measurement method 5 was not related to any metabolic or physiological variables, while measurement method 4 was intermediate in terms of the strength of the associations. These findings suggest that the predictive strength of WHR can vary depending upon the measurement method used.

This study examined the sensitivity and specificity of current methods for classifying morbid obesity in females. Results suggest that current methods for classifying morbid obesity (greater than or equal to 45.5 kg over ideal weight or BMI greater than or equal to 45) do not provide acceptable specificity and sensitivity, respectively. We suggest that additional measurements such as total body fatness determined by hydrodensitometry be used to classify morbid obesity and determine eligibility for aggressive therapeutic interventions for weight loss.