Obesity: much silence makes a mighty noise.

n 2007, the majority of adults in the United States and any developed countries are overweight or obese. It is stimated that 1.6 billion adults worldwide are overeight (body mass index [BMI] 25) and 400 million are bese (BMI 30). Obesity puts millions of people at risk or serious medical conditions such as type 2 diabetes, ardiovascular disease, musculoskeletal disorders, sleep pnea, and some forms of cancer. Children are also inreasingly overweight, with estimates as high as 20 milion globally. Alarmingly, type 2 diabetes and other disases thought to occur almost exclusively in adults are ow prevalent in children. Furthermore, developing ountries, which have dealt with the burden of infectious isease and undernutrition for decades are now facing an psurge of obesity and its crippling health and economic onsequences. Why the silence about obesity until recently? Part of he problem stems from societal notions of what constiutes a “healthy weight” and whether obesity truly fits the efinition of a “disease.” Attitudes about overweight and besity range from acceptance of these conditions as ndicative of prosperity and good health, to a negative erception of obese individuals as lacking self-control. any governments and institutions still consider obesity problem of personal choice that could be reversed imply by deciding to eat less and exercise more. In fact, ome have questioned whether obesity is truly “epiemic.” Attitudes are changing, however, due to the risng incidences of diabetes and other debilitating diseases ttributable to obesity. Moreover, the negative impact of besity on health care budgets and various sectors of the conomy is apparent. Scientific discoveries over the past ecade have also enlightened us about the physiologic rocesses that control weight and metabolism. The drive o eat and store energy mainly as fat is fundamental for aintaining metabolic demands and ensuring survival. or human societies, the amount of available food was imited over several generations. As a result of improveents in agriculture which led to availability of cheap, alatable, and energy dense foods, overconsumption of ood is now the norm, and this coupled with minimal hysical activity has contributed prominently to the risng prevalence of obesity worldwide. This special issue of GASTROENTEROLOGY presents a eries of review articles on the epidemiology of obesity, athophysiology, associated diseases, and management. he contributors are leading experts drawn from a variety f specialties, including epidemiology, endocrinology, etabolism, gastroenterology, behavioral science, and urgery. We emphasize that obesity is multidimensional nd requires an integrated approach to understanding he extent of the problem, causation and health and ocioeconomic consequences. Katherine Flegal (pages 087–2102) reviews the epidemiology of obesity, highighting controversies surrounding adiposity measureent, ethnic differences, childhood obesity, and diseases ssociated with obesity. Jeffrey Flier (pages 2103–2115) iscusses how adipose tissue, the major energy store, egulates energy balance via hormones that act in the rain and peripheral organs. The discovery of leptin and ts neuronal targets in the hypothalamus marked the eginning of concerted efforts to unravel how adipose issue is coupled to feeding, energy expenditure, and egulation of hormones and immune and cardiovascular ystems. Stephen Bloom (pages 2116 –2130) reviews the ole of gut hormones in appetite and weight regulation. ut peptides serve as short-term signals to centers in the indbrain to control meal size and timing, as well as astrointestinal motility and secretions. Ultimately, these unctions impact energy storage in adipose tissue. Daniel rucker (pages 2131–2157) focuses on the biology of lucagon-like peptide (GLP)-1 and glucose-dependent inulinotropic polypeptide (GIP), both secreted within inutes after eating. These incretin hormones facilitate he disposal of nutrients and have profound effects on lucose. Drugs based on potentiation of GLP-1 action