How effective are traditional dietary and exercise interventions for weight loss?

Health care professionals have used restrictive dieting and exercise intervention strategies in an effort to combat the rising prevalence of obesity in affluent countries. In spite of these efforts, the prevalence of obesity continues to rise. This apparent ineffectiveness of diet and exercise programming to reduce obesity has caused many health care providers, obesity researchers, and lay persons to challenge the further use of diet and exercise for the sole purpose of reducing body weight in the obese. The purposes of this paper were to examine the history and effectiveness of diet and exercise in obesity therapy and to determine the best future approach for health promotion in the obese population. A brief survey of the most popular dieting techniques used over the past 40 yr shows that most techniques cycle in and out of popularity and that many of these techniques may be hazardous to health. Data from the scientific community indicate that a 15-wk diet or diet plus exercise program produces a weight loss of about 11 kg with a 60-80% maintenance after 1 yr. Although long-term follow-up data are meager, the data that do exist suggest almost complete relapse after 3-5 yr. The paucity of data provided by the weight-loss industry has been inadequate or inconclusive. Those who challenge the use of diet and exercise solely for weight control purposes base their position on the absence of weight-loss effectiveness data and on the presence of harmful effects of restrictive dieting. Any intervention strategy for the obese should be one that would promote the development of a healthy lifestyle. The outcome parameters used to evaluate the success of such an intervention should be specific to chronic disease risk and symptomatologies and not limited to medically ambiguous variables like body weight or body composition.     

The effects of exercise on the storage and oxidation of dietary fat

Obesity has become a worldwide problem of pandemic proportions. By definition, obesity is the accumulation of excess body fat and it represents the long-term results of positive energy and fat balance. The failures in the regulatory mechanisms leading to the development of obesity are still not well understood, but there is growing evidence that exercise is an important element in obesity prevention. Exercise promotes energy/fat balance while providing beneficial alterations to obesity/overweight-related comorbidities and mortality. Also, exercise, in large part, influences whether the fate of dietary fat is storage or oxidation. Many factors including intensity, duration and type (aerobic vs anaerobic) of exercise, energy expended during exercise and individual fitness level impact the amounts of fat oxidised at any given time. Evidence suggests that moderate-intensity exercise yields the most cumulative (during and post-exercise) fat grams used for substrate in the average individual. All intensities of exercise, however, promote fat oxidation during the post-exercise period. We suggest that it is the effects of exercise on 24-hour fat balance that are most important in understanding the role of exercise in the prevention of fat accumulation and obesity.     

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.     

Exercise considerations for the sedentary,overweight adult

The significant rise in the prevalence of overweight and obesity has increased the importance of addressing this significant public health problem. Exercise appears to be an important factor for addressing the obesity epidemic. This review will focus on the role of exercise in the management of body weight and factors that should be considered when prescribing exercise to overweight adults.     

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.     

Pediatric exercise: truth and/or consequences

Pediatric exercise recommendations are becoming increasingly more important. The recommendation for physical activity in children and adolescents is 60 min/d of moderate to vigorous physical activity. The United States Department of Health and Human Services recommends that vigorous physical activity be included a minimum of 3 d/wk. In addition, strength training, for both the muscle and bone should be included 3 d/wk. As the incidence of childhood obesity increases and the implications towards chronic disease, musculoskeletal issues, and self-esteem issues continue to rise, it is clear that many children do not meet these guidelines. Despite the childhood obesity epidemic, an estimated 38 million children and adolescents participate in organized sports. Both active and inactive children need to be educated on the benefits of exercise, exercise safety, and appropriate exercise recommendations specific to this specialized population.     

Weight loss and exercise: implications for muscle lipid metabolism and insulin action

Implications for Muscle Lipid Metabolism and An accumulation of intramuscular lipid has been reported with obesity and linked with insulin resistance. The purpose of this paper is to discuss: 1) mechanisms that may be responsible for intramuscular lipid accumulation with obesity, and 2) the effects of common interventions (weight loss or exercise) for obesity on skeletal muscle lipid metabolism and intramuscular lipid content. Data suggest that the skeletal muscle of morbidly obese humans is characterized by the preferential partitioning of lipid toward storage rather than oxidation. This phenotype may, in part, contribute to increased lipid deposition in both muscle and adipose tissue, and promote the development of morbid obesity and insulin resistance. Weight loss intervention decreases intramuscular lipid content, which may contribute to improved insulin action. On the other hand, exercise training improves insulin action and increases fatty acid oxidation in the skeletal muscle of obese/morbidly obese individuals. In summary, the accumulation of intramuscular lipid appears to be detrimental in terms of inducing insulin resistance; however, the accumulation of lipid can be reversed with weight loss. The mechanism(s) by which exercise enhances insulin action remains to be determined.     

Exercise, appetite and weight management: understanding the compensatory responses in eating behaviour and how they contribute to variability in exercise-induced weight loss

Does exercise promote weight loss? One of the key problems with studies assessing the efficacy of exercise as a method of weight management and obesity is that mean data are presented and the individual variability in response is overlooked. Recent data have highlighted the need to demonstrate and characterise the individual variability in response to exercise. Do people who exercise compensate for the increase in energy expenditure via compensatory increases in hunger and food intake? The authors address the physiological, psychological and behavioural factors potentially involved in the relationship between exercise and appetite, and identify the research questions that remain unanswered. A negative consequence of the phenomena of individual variability and compensatory responses has been the focus on those who lose little weight in response to exercise; this has been used unreasonably as evidence to suggest that exercise is a futile method of controlling weight and managing obesity. Most of the evidence suggests that exercise is useful for improving body composition and health. For example, when exercise-induced mean weight loss is <1.0 kg, significant improvements in aerobic capacity (+6.3 ml/kg/min), systolic (-6.00 mm Hg) and diastolic (-3.9 mm Hg) blood pressure, waist circumference (-3.7 cm) and positive mood still occur. However, people will vary in their responses to exercise; understanding and characterising this variability will help tailor weight loss strategies to suit individuals.     

Effect of acute endurance and resistance exercise on endocrine hormones directly related to lipolysis and skeletal muscle protein synthesis in adult individuals with obesity

In subjects with obesity, the implementation of long-term exercise intervention increases lean tissue mass and lowers adipose tissue mass. However, data indicate a blunted lipolytic response, and/or skeletal muscle protein synthesis, when subjects with obesity are exposed to acute endurance or resistance exercise, respectively. Therefore, subjects with obesity seem to display a suboptimal physiological response to acute exercise stimuli. It might be hypothesized that hormonal disturbances contribute, at least in part, to these abnormal physiological reactions in the obese. This review discusses the impact of acute endurance and resistance exercise on endocrine hormones directly related to lipolysis and/or skeletal muscle protein synthesis (insulin, [nor]epinephrine, cortisol, growth hormone, testosterone, triiodothyronine, atrial natriuretic peptide, insulin-like growth factor-1), as well as the impact of long-term endurance and resistance exercise intervention on these hormonal responses to acute endurance and resistance exercise. In the obese, some endocrinological disturbances during acute endurance and resistance exercise have been identified: a blunted blood growth hormone, atrial natriuretic peptide and epinephrine release, and greater cortisol and insulin release. These hormonal disturbances might contribute to a suppressed lipolytic response, and/or suppressed skeletal muscle protein synthesis, as a result of acute endurance or resistance exercise, respectively. In subjects with obesity, the impact of acute endurance and resistance exercise on other endocrine hormones (norepinephrine, testosterone, triiodothyronine, insulin-like growth factor-1) remains elusive. Furthermore, whether long-term endurance and resistance exercise intervention might reverse these hormonal disturbances during acute endurance and resistance exercise in these individuals remains unknown.     

单纯肥胖症脂质代谢紊乱的运动防治Ⅰ.有氧运动对饮食诱导单纯性肥胖大鼠脂蛋白代谢的影响

在建立饮食诱导单纯性肥胖及高胆固醇血症实验动物模型基础上，分别观察有氧运动和饮食干预单纯性肥胖大鼠脂蛋白、载脂蛋白水平的影响。结果表明，运动和／或运动与饮食联合干预明显地改善与单纯性肥胖并存的脂质代谢紊乱，降低某些致动脉粥样硬化的高危因素。     

Follow up exercise studies in paediatric obesity: implications for long term effectiveness

OBJECTIVES: To examine the effects of exercise training on paediatric obesity immediately after training and at a one year follow up and to provide recommendations for future research. METHODS: Studies that met the following criteria were included in a meta-analysis: (a) at least six subjects per group; (b) subject groups consisting of children in the 4-17 year age range; (c) pre-test and post-test values for body composition; (d) used exercise such as walking, jogging, cycle ergometry, high repetition resistance exercise, and combinations; (e) training programmes lasting eight weeks or more; (f) full length publications; (g) apparently healthy children. RESULTS: A total of 135 studies of exercise as a method of treatment of paediatric obesity were located. Eight, containing 236 subjects, met our criteria for inclusion. Across all designs and categories, fixed effects modelling yielded significant decreases in the dependent variable percentage body fat immediately (0=1.04 (0.35); 95% confidence interval (CI) 0.41 to 1.6) and one year after the exercise intervention (0=0.84 (0.51); 95% CI 0.22 to 0.94). Forward stepwise linear regression suggested that the percentage body fat measured at the end of exercise training, exercise duration, and programme length accounted for 53-86% of the variance for percentage body fat at one year. CONCLUSIONS: These data indicate that exercise is efficacious for reducing percentage body fat in obese children and adolescents, and that exercise intervention may encourage long term maintenance of the observed gains.     

The hypothalamus and energy balance

In recent years the growing number of molecules implicated in energy homeostasis has raised nearly limitless possibilities for how body-weight regulation might occur. To better understand how energy homeostasis can be achieved, we describe the roles of individual hormonal and neuropeptide signalling pathways in the control of food intake and the means by which obesity can arise from defects in their function. The hypothalamus links the sensing of nutrients to the control of metabolism and feeding behaviour. Disruptions in the mechanisms of central nervous system (CNS) nutrient-sensing alter these homeostatic responses and contribute to the pathophysiology of obesity and type 2 diabetes mellitus. Experimental and epidemiological studies suggest that sleep loss may also play a role in the increased prevalence of diabetes and obesity. The molecular components of the circadian clock are present in the anterior hypothalamus. It is not therefore surprising that there is a close link between sleep and energy metabolism. In this review we also focus on physical exercise as a mechanism to restore physiological rhythm preventing hyperphagia and obesity in humans. Given its ability to reduce cerebral energy demands and therefore promote sleep, physical exercise could be beneficial for maintaining brain function and improving brain plasticity.     

Exercise training in obese children and adolescents: current concepts

Childhood obesity has reached epidemic proportions worldwide and is associated with increased cardiovascular mortality and morbidity in adult life. The increase in fat mass in children and adolescents has occurred concomitantly with a decline in reported time for exercise. Evidence suggests that non-physically active children are more likely to become non-physically active adults and that encouraging the development of physical activity habits in children helps establish patterns that continue into adulthood. Dietary treatment of obesity is relatively ineffective in adults and it has been suggested that prevention of obesity in childhood and adolescence should emphasise increased physical activity rather than diet because of fears relating to the adverse effects of inappropriate eating patterns. Despite this, there are very few randomised controlled studies investigating the efficacy of exercise training in obese children or adolescents and many of the extant studies have been poorly controlled and have not specifically stratified the independent effect of exercise versus dietary modification.This review focuses on the well designed controlled trials that have evaluated the effect of exercise training in obese children and adolescents on body composition, haemodynamic and metabolic variables, cardiovascular fitness, muscular strength and vascular function. These studies indicate that, although exercise training does not consistently decrease bodyweight or body mass index, it is associated with beneficial changes in fat and lean body mass, emphasising the importance of comprehensive assessment of body composition in future exercise-training studies. Exercise training improves cardiovascular fitness and muscular strength; however, it seems to have little effect on blood lipid profile or blood pressure in obese young people. Importantly, recent studies have demonstrated that exercise training improves vascular endothelial function, an important surrogate measure that may predict future atherosclerotic risk in obese children and adolescents. Given that improvement in vascular function in these training studies occurred in the absence of changes in lipid fractions, haemodynamic variables or glucose metabolism, exercise appears to have a direct beneficial effect on the vasculature, in addition to its putative benefits through risk-factor modification.     

Effects of obesity on the biomechanics of walking at different speeds

PURPOSE: Walking is a recommended form of exercise for the treatment of obesity, but walking may be a critical source of biomechanical loads that link obesity and musculoskeletal pathology, particularly knee osteoarthritis. We hypothesized that compared with normal-weight adults 1) obese adults would have greater absolute ground-reaction forces (GRF) during walking, but their GRF would be reduced at slower walking speeds; and 2) obese adults would have greater sagittal-plane absolute leg-joint moments at a given walking speed, but these moments would be reduced at slower walking speeds. METHODS: We measured GRF and recorded sagittal-plane kinematics of 20 adults (10 obese and 10 normal weight) as they walked on a level, force-measuring treadmill at six speeds (0.5-1.75 m.s(-1)). We calculated sagittal-plane net muscle moments at the hip, knee, and ankle. RESULTS: Compared with their normal-weight peers, obese adults had much greater absolute GRF (N), stance-phase sagittal-plane net muscle moments (N.m) and step width (m). CONCLUSIONS: Greater sagittal-plane knee moments in the obese subjects suggest that they walked with greater knee-joint loads than normal-weight adults. Walking slower reduced GRF and net muscle moments and may be a risk-lowering strategy for obese adults who wish to walk for exercise. When obese subjects walked at 1.0 versus 1.5 m.s(-1), peak sagittal-plane knee moments were 45% less. Obese subjects walking at approximately 1.1 m.s(-1) would have the same absolute peak sagittal-plane knee net muscle moment as normal-weight subjects when they walk at their typical preferred speed of 1.4 m.s(-1).     

Exercise as a partial therapy for the extremely obese

The management of the extremely obese patient is best accomplished by a multidisciplinary approach which includes exercise training as an integral component. While diet alone is a potent factor in improving the metabolic complications associated with obesity, the combination of diet and exercise training can further improve these complications and greatly enhance cardiorespiratory function. Although the fitness of extremely obese people is low, individualized exercise programs can be used to safely and progressively train these patients, reduce fatigue, and greatly increase maximum work tolerance. Additional benefits derived from exercise training include improved insulin-mediated glucose utilization, lower serum lipid concentrations, and improved psychological distress scores and anxiety levels. Thus, exercise training can contribute to the success of a weight reducing program by improving metabolic, cardiorespiratory, and psychological factors. Additional important interventions in a multidisciplinary treatment of severe obesity include psychiatric, psychosocial, and vocational counseling.     

Acute exercise and subsequent nutritional adaptations: what about obese youths?

The imbalance between energy expenditure and energy intake is the main factor accounting for the progression of obesity. For many years, physical activity has been part of weight-loss programmes to increase energy expenditure. It is now recognized that exercise can also affect appetite and energy consumption. In the context of seeking new obesity treatments, it is of major interest to clarify the impact of physical exercise on energy intake. Many reviews on this topic have been published regarding both lean and overweight adults, and this review focuses on the relationships between acute exercise and the short-term regulation of energy intake in lean and overweight or obese youths. The current literature provides very few data regarding the impact of exercise on subsequent energy intake and perceived and measured appetite in children and adolescents, mainly because of methodological difficulties in the assessment of both energy intake and expenditure. It has been long suggested that energy intake was regulated after exercise in order to compensate for the exercise-induced energy expenditure and then preserve energy balance. This overview underlines that the energy expended during exercise is not the main parameter that influences subsequent energy intake in both lean and overweight/obese children and adolescents, and that factors such as the duration or intensity of exercise may have larger impact. The effects of acute exercise on the following nutritional adaptations (energy intake and appetite feelings) remain inconclusive in lean youths, mainly due to the lack of data and the disparity of the methodologies used. Studies in overweight or obese children and adolescents are confronted with the same difficulties, and the few available data suggest that intensive exercise (>70% maximal oxygen consumption) can induce a reduction in daily energy balance, as a result of its anorexigenic effect in obese adolescents. However, further studies are needed to clarify the impact of acute exercise on subsequent nutritional adaptations and appetite-related hormones in children and adolescents, and to investigate the effect of chronic exercise programmes.     

Interventions for weight loss and weight gain prevention among youth: current issues

The recent increase in the prevalence of paediatric obesity is one of the most pressing public health concerns today because of the immediate and long term health consequences associated with this often intractable disease. Efforts are currently being made to reduce the prevalence of paediatric obesity. Youth weight loss studies have produced significant long term results. Most of these programmes included behaviour modification, diet and exercise. Studies have suggested that lifestyle exercise programmes may produce the best long term results. Effective components of these programmes appear to be parental involvement, reduced intake of foods having high energy density and reductions in physical inactivity. Future weight loss studies need to determine the type, intensity, and duration of exercise that will produce acceptable adherence and consequent long term weight loss, and to ascertain the reinforcing factors that determine youth behaviour choice. Weight gain prevention interventions for youth are clearly in their infancy. This review describes 3 completed and 2 ongoing weight gain prevention trials. One study showed reductions in the prevalence of obesity among junior high school girls, but not among boys. Another study among elementary school students showed significant mean decreases in body mass index in boys and girls following an intervention specifically to reduce time spent viewing television. Whether these studies altered food intake or increased physical activity remains unclear. A combination of weight loss treatment and weight gain prevention strategies employed in parallel is likely to yield the greatest benefits. Development and testing of novel intervention strategies, using innovative behavioural approaches to increase the likelihood that children will adopt healthy dietary, physical activity, and sedentary behaviour patterns, holds great promise to significantly reduce the epidemic of obesity.     

影响高血压病左室重构的因素探讨

 目的探讨高血压病患者引起左室重构的主要危险因素.方法将患高血压病伴肥胖、经心脏B超证实有左室重构者42例,血压管理经24h血压监测,进行随访、追踪5 a,采用logistic回归分析.结果收缩压持续升高伴肥胖者左室重构的系数为1.183,危险度为3.513;长期降压、减肥、运动、饮茶的危险度为负值.结论收缩压持续升高伴肥胖者是引起左室重构的主要危险因素;降压、减肥、运动、饮茶是抑制左室重构的因素.     

Factors common to successful therapy for the obese patient

The majority of patients treated for obesity regain lost weight after treatment. We speculate on what might be done to improve long-term success rates by examining the factors associated with success or relapse. An emphasis on exercise and prescribing more gradual changes in diet and exercise appears to be associated with better outcomes. There may be a need to conceptualize obesity as a food dependency disorder not amenable to self-control strategies. External social control through peer support groups may be indicated to help patients through temptations.