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Obesity: more pieces for the puzzle
Best Practice & Research Clinical Endocrinology and Metabolism Vol. 16, No. 4, pp. vii±viii, 2002
doi:10.1053/beem.2002.0229, available online at http://www.idealibrary.com on
Preface Obesity: more pieces for the puzzle There are several reasons why it is timely to review the quest to obtain a better understanding of the causes and consequences of obesity. It is clear that the incidence of obesity worldwide (particularly in developing countries) is increasing at an alarming rate and the number of clinically relevant problems linked to obesity is also growing. Overweight and obesity and the complications of these conditions is also occurring in much younger age groups, highlighting the need to understand more about how obesity arises and what can be done to alleviate or prevent obesity. We are facing an epidemic of obesity and the need to increase the research eort into controlling this problem and reducing the associated health costs is now being recognized by governments. The aim of this edition is to highlight the extent of the problem and update progress in some of the major areas of research into the causes and consequences of obesity. The increasing prevalence of obesity and how this varies in dierent ethnic groups is discussed in Chapter 1 by Dr Caterson and Dr Gill. These authors also provide some thoughts on the environmental and social strategies that could help in the prevention of obesity. Although there is a clear indication that genetic background plays a major part in the development of obesity, eorts to identify genes contributing to obesity have been relatively disappointing. However, in Chapter 2 Dr Comuzzie reviews the data showing that a genome scanning approach to ®nding genes for obesity is now producing some highly signi®cant ®ndings across dierent populations. The role of the hypothalamus in the regulation of energy balance is reviewed in Chapter 3 by Dr Sainsbury and colleagues. Particular attention is paid to our increased understanding of the neuropeptides and neuronal pathways involved in initiating and inhibiting food intake and also the role of hypothalamic neurones in regulating endocrine axes. There is also an increasing amount of data suggesting that adipose tissue produces a large number of factors apart from leptin that may be important in carbohydrate and lipid homeostasis. Dr Prins outlines the types of factors produced by adipose tissue in Chapter 4 and summarizes the evidence that these adipose tissue hormones play a role in the health problems associated with accumulation of excess body fat. After its discovery in 1994 studies on the role of leptin have focussed mainly on its action as a peripheral signal to the brain, involved in controlling food intake and energy expenditure. Chapter 5 by Drs Muoio and Dohm reviews the increasing evidence that leptin may also act via tissue receptors to alter lipid metabolism in peripheral tissues. Exercise always plays a role in any energy balance equation and Chapter 6 by Dr Blaak and Dr Saris deals with the role of exercise in weight loss and maintenance of weight loss. In Chapter 7 Dr Levine de®nes non-exercise activity thermogenesis (NEAT) and discusses the contribution of NEAT to total energy expenditure and the possibility of it being an important factor in the genesis of obesity. c 2002 Published by Elsevier Science Ltd. 1521±690X/02/$ - see front matter *
viii Preface
The increased risk of heart disease, type 2 diabetes and lipid disorders in obese subjects is well established but there is an emerging link between obesity and fatty liver which implies that liver disease may also be an important health problem in the obese. In Chapter 8 Dr Scheen and Dr Luyckx put forward the arguments for nonalcoholic steatohepatitis (NASH) being included in the cluster of diseases known as the metabolic or insulin resistance syndrome. Finally, in Chapter 9 Dr Finer reviews the current state of pharmacotherapy for obesity, outlining the current use of compounds for weight control and suggesting where the future lies with regard to a pharmacological approach to weight control. This edition showcases the latest approaches being used to understand an increasingly important health issue. There are new aspects of the energy balance equation such as NEAT that need to be considered, as does the expanding list of adipose tissue hormones and their possible action on central and peripheral processes. We know more about the brain processes that control energy balance and more about which genes contribute to an increased risk of obesity. Hopefully prevention or at least better treatments for obesity and its complications will ¯ow from the increased research eort being mounted to combat this disease. I would like to thank all the contributors to this edition for the eort they put into producing their excellent reviews and I would also like to thank the editorial sta for their support and hard work in helping complete this project. Greg J. Cooney
doi:10.1053/beem.2002.0229, available online at http://www.idealibrary.com on
Preface Obesity: more pieces for the puzzle There are several reasons why it is timely to review the quest to obtain a better understanding of the causes and consequences of obesity. It is clear that the incidence of obesity worldwide (particularly in developing countries) is increasing at an alarming rate and the number of clinically relevant problems linked to obesity is also growing. Overweight and obesity and the complications of these conditions is also occurring in much younger age groups, highlighting the need to understand more about how obesity arises and what can be done to alleviate or prevent obesity. We are facing an epidemic of obesity and the need to increase the research eort into controlling this problem and reducing the associated health costs is now being recognized by governments. The aim of this edition is to highlight the extent of the problem and update progress in some of the major areas of research into the causes and consequences of obesity. The increasing prevalence of obesity and how this varies in dierent ethnic groups is discussed in Chapter 1 by Dr Caterson and Dr Gill. These authors also provide some thoughts on the environmental and social strategies that could help in the prevention of obesity. Although there is a clear indication that genetic background plays a major part in the development of obesity, eorts to identify genes contributing to obesity have been relatively disappointing. However, in Chapter 2 Dr Comuzzie reviews the data showing that a genome scanning approach to ®nding genes for obesity is now producing some highly signi®cant ®ndings across dierent populations. The role of the hypothalamus in the regulation of energy balance is reviewed in Chapter 3 by Dr Sainsbury and colleagues. Particular attention is paid to our increased understanding of the neuropeptides and neuronal pathways involved in initiating and inhibiting food intake and also the role of hypothalamic neurones in regulating endocrine axes. There is also an increasing amount of data suggesting that adipose tissue produces a large number of factors apart from leptin that may be important in carbohydrate and lipid homeostasis. Dr Prins outlines the types of factors produced by adipose tissue in Chapter 4 and summarizes the evidence that these adipose tissue hormones play a role in the health problems associated with accumulation of excess body fat. After its discovery in 1994 studies on the role of leptin have focussed mainly on its action as a peripheral signal to the brain, involved in controlling food intake and energy expenditure. Chapter 5 by Drs Muoio and Dohm reviews the increasing evidence that leptin may also act via tissue receptors to alter lipid metabolism in peripheral tissues. Exercise always plays a role in any energy balance equation and Chapter 6 by Dr Blaak and Dr Saris deals with the role of exercise in weight loss and maintenance of weight loss. In Chapter 7 Dr Levine de®nes non-exercise activity thermogenesis (NEAT) and discusses the contribution of NEAT to total energy expenditure and the possibility of it being an important factor in the genesis of obesity. c 2002 Published by Elsevier Science Ltd. 1521±690X/02/$ - see front matter *
viii Preface
The increased risk of heart disease, type 2 diabetes and lipid disorders in obese subjects is well established but there is an emerging link between obesity and fatty liver which implies that liver disease may also be an important health problem in the obese. In Chapter 8 Dr Scheen and Dr Luyckx put forward the arguments for nonalcoholic steatohepatitis (NASH) being included in the cluster of diseases known as the metabolic or insulin resistance syndrome. Finally, in Chapter 9 Dr Finer reviews the current state of pharmacotherapy for obesity, outlining the current use of compounds for weight control and suggesting where the future lies with regard to a pharmacological approach to weight control. This edition showcases the latest approaches being used to understand an increasingly important health issue. There are new aspects of the energy balance equation such as NEAT that need to be considered, as does the expanding list of adipose tissue hormones and their possible action on central and peripheral processes. We know more about the brain processes that control energy balance and more about which genes contribute to an increased risk of obesity. Hopefully prevention or at least better treatments for obesity and its complications will ¯ow from the increased research eort being mounted to combat this disease. I would like to thank all the contributors to this edition for the eort they put into producing their excellent reviews and I would also like to thank the editorial sta for their support and hard work in helping complete this project. Greg J. Cooney