Exercise and obesity

Obesity, prevalent in industrialised societies, is most usefully categorised by means of the body mass index (BMI-weight/height2). A body mass index of greater than 25 is associated with increasingly poor prognosis. Weight reduction has been shown to be beneficial with respect to both mortality and morbidity. Excess weight results from an imbalance between energy input and expenditure in favour of the former. Weight reduction may be promoted by reducing energy input and/or stimulating expenditure. It is tempting to postulate that inactivity may be a factor in both the development and subsequent continuation of obesity via an effect on energy intake, fat-free mass or energy expenditure. Although available data are by no means conclusive, the majority of evidence suggests that obesity is not associated with either reduced activity or energy expenditure. Likewise, exercise appears not to promote a change in body composition in favour of lean body mass or have a prolonged thermogenic effect beyond the duration of the activity. Exercise alone appears largely ineffective regarding weight loss and almost certainly has to be coupled with calorie reduction. It must be remembered that the exercise tolerance in the severely obese (BMI greater than 40) is very poor. Such individuals must be closely supervised during a specifically graded programme. What is also apparent is the high drop-out rate of individuals recruited into exercise programmes. In those who voluntarily engage in physical activity, the incidence of ischaemic heart disease may be reduced, which may or may not be related to a direct exercise effect on known cardiovascular risk factors. Cigarette smoking is usually less common and general life-style may be more prudent. Whether exercise in obese subjects could have a similar effect remains unknown. Although much of the data on exercise in general and on obesity in particular are negative, it appears unwise to adopt a totally nihilistic approach. Increased physical activity should be encouraged as it is possible that the discipline involved in regularly undertaking such activity may be more conducive to weight loss, a feeling of well-being and fitness and a general change of life-style for the better. Long term it may also afford additional benefit by reducing liability to ischaemic heart disease.     

Exercise in obesity management

Obesity is considered a global epidemic by the World Health Organization in both developed and developing countries. It is associated with a higher risk of cardiovascular disease, diabetes mellitus, cancer and other clinical conditions. Visceral fat is the major responsible for metabolic complications, such as insulin-resistance, and it acts as an endocrine organ producing adipokines involved in lipidic and glycaemic metabolism. TNF-α and IL-6, produced by adipose tissue, increase NADPH oxidase activity activating protein kinase C and NFκB leading to an higher oxidative stress. The obesity management includes physical activity: aerobic training improves lipid profile and insulin sensitivity while resistance training increases lean body mass and basal metabolism and has beneficial effects on bone mineral density and glucose tolerance. An exercise program should include 30 to 45 minutes of moderate intensity activity performed 3 to 5 days a week. Weight loss is also associated with lower blood pressure and improved oxidative status, confirmed by reduced oxidative stress markers and increased antioxidant protection. An inverse association between indicators of systemic inflammation and physical activity has been demonstrated, so exercise training may reduce endothelial damage and cardiovascular risk.     

Effect of endurance training supplemented with green tea extract on substrate metabolism during exercise in humans

Endurance training and ingestion of green tea extract (GTE), composed mainly of tea catechins (TC), are well known to enhance fat metabolism. However, their synergistic effects remain to be fully elucidated. We tested the hypothesis that endurance training supplemented with GTE would further accelerate whole‐body fat utilization during exercise, compared with training alone, in humans. Twelve healthy male subjects [peak oxygen consumption (), 50.7 ± 1.3 (SEM) mL/kg/min] were divided into two groups: GTE and placebo (PLA) groups. Subjects in both groups performed a cycle ergometer exercise at 60% of for 60 min/day, 3 days/week, and daily ingested 572.8 or 0 mg TC in GTE and PLA groups for 10 weeks, respectively. Before and after training, respiratory gas exchange was measured during 90‐min exercise at pre‐training ～55% of . After training, the average respiratory exchange ratio during exercise remained unchanged in the PLA group (post‐training: 0.834 ± 0.008 vs pre‐training: 0.841 ± 0.004), whereas it was lower in the GTE group (post‐training: 0.816 ± 0.006 vs pre‐training: 0.844 ± 0.005, P<0.05). These results suggest that habitual GTE ingestion, in combination with moderate‐intense exercise, was beneficial to increase the proportion of whole‐body fat utilization during exercise.     

Exercise considerations in hypertension,obesity, and dyslipidemia

Sports medicine practitioners who care for a wide array of athletes and active individuals will consistently face issues regarding chronic cardiovascular diseases and their associated risk factors. Among these, hypertension, obesity, and dyslipidemia are common clinical conditions that may be encountered even amongst elite caliber athletes. Consequently, those entrusted with the care of this active population must recognize the presence of these disorders and feel comfortable with their management in the face of continued sports or exercise participation. This article reviews the pathophysiology of these conditions as they relate to athletes and outlines the value of continued exercise in the management of each of these entities while addressing the specific and unique treatment needs of active individuals.     

Body composition analysis of obesity and hepatic steatosis in mice by relaxation compensated fat fraction (RCFF) MRI

Purpose:

To develop and validate a quantitative magnetic resonance imaging (MRI) methodology for phenotyping animal models of obesity and fatty liver disease on 7T small animal MRI scanners.

Materials and Methods:

A new MRI acquisition and image analysis technique, relaxation‐compensated fat fraction (RCFF), was developed and validated by both magnetic resonance spectroscopy and histology. This new RCFF technique was then used to assess lipid biodistribution in two groups of mice on either a high‐fat (HFD) or low‐fat (LFD) diet.

Results:

RCFF demonstrated excellent correlation in phantom studies (R² = 0.99) and in vivo compared to histological evaluation of hepatic triglycerides (R² = 0.90). RCFF images provided robust fat fraction maps with consistent adipose tissue values (82% ± 3%). HFD mice exhibited significant increases in peritoneal and subcutaneous adipose tissue volumes in comparison to LFD controls (peritoneal: 6.4 ± 0.4 cm³ vs. 0.7 ± 0.2, P < 0.001; subcutaneous: 14.7 ± 2.0 cm³ vs. 1.2 ± 0.3 cm³, P < 0.001). Hepatic fat fractions were also significantly different between HFD and LFD mice (3.1% ± 1.7% LFD vs. 27.2% ± 5.4% HFD, P = 0.002).

Conclusion:

RCFF can be used to quantitatively assess adipose tissue volumes and hepatic fat fractions in rodent models at 7T. J. Magn. Reson. Imaging 2012;35:837–843. © 2011 Wiley Periodicals, Inc.     

Exercise prescription for the prevention of obesity in adolescents

Childhood obesity is a major public health problem and poses important challenges for both health care and school-centered environments. Each faces difficulties in successfully addressing this problem: school personnel report lack of training in intervention, and health providers report ineffective office-based intervention strategies. With coordination of interventions in the school and office, prevention and treatment of childhood obesity can be improved. Toward this, the function of prescribing exercise as a preventive treatment can be very effective. This review evaluates recent literature upon the health care provider's role in and out of the medical office at prescribing exercise and the associated health benefits of exercise for children. Thus, health professionals caring for children and adolescents are in a key position to help prevent and treat obesity by promoting behavioral and environmental changes. Although the evidence base is insufficient to provide specific guidelines for assessment and treatment of all aspects of child and adolescent obesity, the following recommendations reflect critical reviews of the literature and are based upon expert committee guidelines.     

Exercise and intestinal polyp development in APCMin mice

PURPOSE: Epidemiological evidence suggests that physical activity protects against colon cancer. We previously used a mouse predisposed to intestinal polyps (APCMin) to evaluate this association and found the suggestion of fewer polyps in exercised males but not females. The present study was designed to further explore the potential exercise x sex interaction on polyp development and to begin to look at potential mechanisms. METHODS: Six-week-old APCMin mice (N = 60 males; 60 females) were randomly assigned to one of two groups by sex: treadmill running at 20 m.min-1, 5% grade, 45 min.d-1, 5 d.wk-1 (EX) or nonrunning controls (CON) (N = 30 per group). EX mice ran in running wheels while in quarantine (weeks 0-3), followed by treadmill running weeks 3-8. Body weights were measured weekly. Urine was collected at 5 wk and fasting blood at 7.5 wk. Body composition was measured, serum was frozen, and polyp number and size were measured at sacrifice. RESULTS: EX resulted in lower body weights (P < 0.01) and reduced fat mass (P < 0.01). Fasting glucose was lower in EX (P < 0.01), and leptin was lower in EX (P = 0.05) compared with CON. EX did not affect serum insulin-like growth factor-1 or urinary corticosterone. Total polyp number and size were not statistically different between groups; however, there were fewer jejunal polyps in EX (3.6 +/- 0.7, mean +/- SE) versus CON males (5.2 +/- 0.8; P = 0.04) and an even larger difference when only the consistent runners were kept in the analysis (2.7 +/- 0.5 in EX; P = 0.01). CONCLUSION: Despite favorable changes in body composition, blood glucose, and leptin, 8 wk of running resulted in only minor changes related to polyp development in male but not female APCMin mice.     

Maximal fat oxidation during exercise in trained men

Fat oxidation increases from low to moderate exercise intensities and decreases from moderate to high exercise intensities. Recently, a protocol has been developed to determine the exercise intensity, which elicits maximal fat oxidation rates (Fat(max)). The main aim of the present study was to establish the reliability of the estimation of Fat(max) using this protocol (n = 10). An additional aim was to determine Fat(max) in a large group of endurance-trained individuals (n = 55). For the assessment of reliability, subjects performed three graded exercise tests to exhaustion on a cycle ergometer. Tests were performed after an overnight fast and diet and exercise regime on the day before all tests were similar. Fifty-five male subjects performed the graded exercise test on one occasion. The typical error (root mean square error and CV) for Fat(max) and Fat(min) was 0.23 and 0.33 l O(2) x min(-1) and 9.6 and 9.4 % respectively. Maximal fat oxidation rates of 0.52 +/- 0.15 g x min(-1) were reached at 62.5 +/- 9.8 % VO(2)max, while Fat(min) was located at 86.1 +/- 6.8 % VO(2)max. When the subjects were divided in two groups according to their VO(2)max, the large spread in Fat(max) and maximal fat oxidation rates remained present. The CV of the estimation of Fat(max) and Fa(min) is 9.0 - 9.5 %. In the present study the average intensity of maximal fat oxidation was located at 63 % VO(2)max. Even within a homogeneous group of subjects, there was a relatively large inter-individual variation in Fat(max) and the rate of maximal fat oxidation.     

Regulation of lipid mobilization and oxidation during exercise in obesity

Regulation of lipid mobilization and oxidation during exercise in obesity. Exerc. Sport Sci. Rev. Vol. 29, No. 1, pp 42-46, 2001. Obesity is associated with metabolic disorders that may be related to alterations in lipid mobilization and oxidation. Although exercise is essential for successful weight management, the regulation of fatty acid metabolism during exercise in obesity is unclear. This review discusses factors that regulate fat metabolism during exercise and the effects of endurance training on these responses.     

基层士兵脂肪含量的测量与肥胖分析

 目的 了解基层士兵肥胖发生情况.方法 对3844名士兵的身高(cm)、体重(kg)进行测量,计算体质指数(BMI);应用BFA-100人体脂肪分析仪,测量其生物电阻抗(Ω)、体脂重(kg)、体脂百分比(F%).应用BMI法和F%法分别对士兵进行肥胖判定.对不同年龄、不同藉贯、不同等级、不同职务士兵肥胖发生情况进行比较.结果 3844名士兵身高(172.7±4.3)cm、体重(65.7±6.7)kg、BMI(22.1±2.3)、生物电阻抗(504.8±56.5)Ω、体脂重(12.7±3.7)kg、F%(19.0±4.0).两种方法对肥胖的检出率分别为22.9%和34.6%.不同年龄组、不同等级及不同职务士兵的肥胖检出率具有明显差异.不同藉贯士兵肥胖检出率无明显差异.与10年前相比,基层士兵的肥胖检出率明显增加.结论 应用生物电阻抗法测量F%,并依F%判断肥胖方法科学,结果准确.目前,基层士兵肥胖发生率高,应引起高度重视.     

Efficacy of chlorhexidine,photosensitizers, green tea extract,and propolis on bond integrity and microleakage of caries-affected dentin: An in-vitro study

AimThe current study aimed to evaluate the efficacy of chlorhexidine (CHX), phycocyanin photosensitizer (PC), green tea extract (GTE), and propolis (PP) on the adhesive bond integrity and microleakage of caries-affected dentin (CAD) using etch and rinse adhesive system.Material and methodsA sum of 80 extracted human mandibular molars was collected and assessed using ICDAS criteria. Randomly CAD samples were treated with different disinfectants (n = 20) each CHX, PC, GTE, and PP. After ensuring disinfection, specimens were rehabilitated with bulk-fill composite resin employing etch and rinse adhesive system. SBS testing was performed by engaging (n=10) specimens in a universal testing machine. Microleakage analysis was performed by using the dye penetration technique.A stereomicroscope under 40× magnification was utilized for analyzing failure modes. Statistical analysis was accomplished by using the ANOVA and Tukey's post hoc tests (p<0.05).ResultsHighest bond strength was displayed by CAD disinfection with CHX and bonded to resin cement (15.33 ± 0.14 MPa). Whereas, the lowest SBS bond value was presented by Group 2 dentin surface disinfection with PC. CAD disinfected with GTE, PP and CHX demonstrated comparable SBS(p>0.05). The maximum microleakage score was exhibited when CAD bonded to resin cement disinfected with PP. While the minimum microleakage score was unveiled CAD bonded to resin cement sanitized with CHXConclusionCaries-affected dentin bonded to resin cement, chlorhexidine exhibited the highest adhesive shear bond strength with a minimal microleakage score using etch and rinse adhesive system.     

Exercise and diet in obesity treatment: an integrative system dynamics perspective

PURPOSE: Demonstrate the utility of System Dynamics computer modeling to study and gain insight into the impacts of physical activity and diet on weight gain and loss. METHODS: A holistic System Dynamics computer model is presented that integrates the processes of human metabolism, hormonal regulation, body composition, nutrition, and physical activity. These processes are not independent of one another, and the model captures the complex interdependencies between them in the regulation of body weight and energy metabolism. The article demonstrates how such an integrative simulation model can serve as a viable laboratory tool for controlled experimentation to investigate the impacts of physical activity and diet on body weight and composition. RESULTS: In one experiment, weight loss from a moderate level of daily exercise was slightly less than the loss from dieting. Although exercise did have a favorable impact on body composition by protecting against the loss in fat-free mass (FFM), it, however, failed to blunt the drop in resting energy expenditure (REE) that accompanies diet-based weight loss. The smaller loss in FFM did indeed induce a smaller drop in REE, however, the preservation of FFM also affected a relatively larger loss in FM, which, in turn, induced a larger adaptive reduction in the metabolic rate. The two adaptations almost totally offset one another, causing minimal differences in REE. In a second experiment, exercise regimens of moderate- to high-level intensity proved counterproductive as weight-reducing strategies. However, when the diet was changed from a balanced composition to one that was highly loaded with carbohydrates, it became possible to sustain the intense exercise regimen over the experimental period and achieve a significant drop in body weight. CONCLUSION: The results underscore the significant interaction effects between physical activity, diet, and body composition and demonstrate the utility of computer-based experimentation to study, gain insight into, and make predictions about their dynamics.     

Exercise training in obesity lowers blood pressure independent of weight change

PURPOSE: We used the rabbit model of obesity and exercise training to determine effects of exercise training during the development of obesity on resting blood pressure and heart rate, ventricular hypertrophy, blood volume, and hormonal profile. METHODS: Female New Zealand white rabbits were assigned to one of four groups: lean sedentary (L-S, N = 17), lean exercise-trained (L-EX, N = 16), obese sedentary (O-S, N = 18), and obese exercise-trained (O-EX, N = 15). Lean rabbits were fed a maintenance diet whereas obese rabbits were fed an ad libitum high fat (10% added fat) diet. Simultaneously, exercise-trained animals underwent a progressive treadmill exercise training protocol for 12 wk. After 12 wk of diet and exercise regimens, resting blood pressure and heart rate were measured from a central ear artery catheter. Ventricular hypertrophy was evaluated using wet ventricular weights. Blood volume was measured using the Evans blue dye procedure; hormonal profile was evaluated from arterial plasma/serum samples. RESULTS: After 12 wk, O-S and O-EX had similar body weights and similar percentage increases in body weight. Despite similar body weights, O-EX had an approximate 6-mm Hg lower mean blood pressure compared with the elevated pressure seen in O-S (P < or = 0.05). Obese rabbits had greater resting heart rate, plasma cholesterol and triglycerides, and plasma renin activity compared with lean rabbits, and these values were unaffected by exercise training. Plasma and blood volumes, as well as plasma insulin, cortisol, and aldosterone were unaffected by exercise training. CONCLUSION: These data suggest that exercise training, in the absence of differences in body weight, may be useful in the reduction of obesity-induced hypertension but that other therapies may be needed in order to control other cardiovascular risk factors.     

香烟和绿茶对辐射致突变效应的影响

目的 探讨日常生活中的香烟和绿茶因素对辐射致突变效应的影响,为放射损伤的防护提供基础资料。方法 按照析因实验设计,香烟、绿茶和辐射3因素用与不用2个水平（23）分为8个实验组。动物分组采用分层随机化。各组分别给予香烟、绿茶和辐射,以及3因素的各种不同组合,其中1组为空白对照组。单盲法测定小鼠骨髓嗜多染红细胞微核率。实验数据用SAS 8.0分析软件进行析因实验设计的方差分析。结果 对于诱发骨髓细胞突变的效应,辐射因素、香烟因素、绿茶因素,其中香烟与辐射的交互作用差异有统计学意义（P＜0.01）,绿茶与辐射的交互作用差异有统计学意义（P＜0.05）。结论 辐射和吸烟均具有致突变作用,绿茶具有抑制细胞突变的作用,吸烟与辐射有协同致突变作用,绿茶对辐射的致突变性有拮抗作用。     

Regulation of skeletal muscle fat oxidation during exercise in humans

Fat and carbohydrate are the major energy substrates during aerobic exercise in well-fed humans. The regulation of fat metabolism during exercise has not been as thoroughly studied as carbohydrate metabolism, especially in human skeletal muscle. Traditionally, it was believed that the regulation of skeletal muscle fat metabolism was mainly at the level of the delivery of free fatty acids to the muscle (adipose tissue lipolysis) and transport of the long chain fatty acids into the mitochondria. It is now known that the transport of fatty acids into the muscle cell and the regulation of muscle triacylglycerol lipase activity are also important sites of regulation. New lines of research are currently underway examining the regulation of fat metabolism in skeletal muscle at the level of fat transport across the sarcolemmal and mitochondrial membranes and regulation of TG lipase activity in both rodent and human models. A major goal of this research is to determine the regulatory signals that control the up-regulation of fat metabolism during the transition from rest to low and moderate aerobic exercise (30-65% (.)VO(2max)) and the down-regulation that occurs when exercising at intense aerobic exercise (approximately 85% (.)VO(2max)). Although it is expected that the signals that activate carbohydrate metabolism during exercise (Ca and free ADP, AMP, and P(i)) would also play a role in fat metabolism, this has not been demonstrated to date.     

Effects of aerobic fitness on fat oxidation and body fatness

OBJECTIVE: This study investigated the contributions of physical fitness and body composition to 24-h fat oxidation in adults under sedentary conditions in a whole-room calorimeter. METHODS: The following measurements were studied in 109 adults (49 male/45 female) at least 36 h after a bout of exercise: 1) aerobic fitness level assessed by VO2max, 2) body composition determined by underwater weighing, 3) resting metabolic rate (RMR) after an overnight fast, and 4) 24-h energy expenditure (EE) and substrate oxidation determined in a whole-room calorimeter. While in the calorimeter, subjects were provided with a diet (15% protein, 30% fat, and 55% carbohydrate) estimated to produce energy balance on a sedentary day and of similar nutritional composition to their daily dietary intake. RESULTS: We found strong negative correlations between VO2max and % body fat in both male and female subjects, but no relationship between VO2max and 24-h EE under the sedentary conditions of this study. In male subjects, VO2max (mL O2 x kg(-1) fat-free mass x min(-1)) was negatively related to fat oxidation (r = -0.397, P < 0.005), and fat oxidation was more closely related to fat mass (r = 0.434, P < 0.0002) than to fat-free mass (r = 0.165, NS). In contrast, none of these relationships were significant in females. CONCLUSION: The results show that in male subjects under sedentary conditions, 24-h fat oxidation is positively related to body fat mass and negatively related to VO2max (the marker used here for level of physical fitness). This supports our hypothesis that regularly active males maintain lower body fat stores as the low contribution to daily fat oxidation from a lower body fat mass is counterbalanced by the high contribution to fat oxidation from daily physical activity. The lack of a relationship between VO2max and 24-h EE under the sedentary conditions of this study suggests that the major effects of physical activity on total daily EE and fat oxidation may occur during and relatively quickly after an exercise bout. Further, these data also suggest that cessation of regular exercise will likely be associated with a high risk of positive fat balance and weight gain.