Editorial [ Obesity and the Lung Guest Editors: Neil S. Cherniack and E. Paul Cherniack ]

Both smoking and overeating are very bad habits with serious adverse consequences for health [1, 2]. They are interrelated. Often, smoking is begun as a way to lose weight. On the other hand, smoking cessation is often accompanied by weight gain, which offsets some of the beneficial effects of not smoking [3, 4]. Both smoking and overeating can cause widespread damage to the body [5, 6] and interfere with breathing [7-9]. This hot topic issue of Current Respiratory Medicine Reviews considers obesity related lung disease within the broader context of energy homeostasis. It includes some of the final contributions of Musa A. Haxhiu, one of the pioneers in the neural control of energy homeostasis. This issue is unique in bringing together overviews of the effects of obesity on the respiratory system with summaries of the mechanisms of obesity and the systemic effects of adiposity. Particular attention is given to the medical and surgical treatment of obesity. In addition to its mass loading effects on the respiratory muscles and the upper airways, it is now appreciated that adipose tissue is metabolically active and the source of chemicals such as cytokines, leptin, and adioponectin that can exert systemic effects on the brain, immune regulation, the endocrine and other systems [10, 11]. Sleep apnea is an important example of how both the mechanical and systemic results of obesity play significant roles in causing and perpetuating the disease [12, 13]. Since sleeplessness is associated with overeating and weight gain, the sleep apnea patient may sometimes find himself trapped in a dangerous cycle [14]. Obesity and sleep apnea like hyperlipidemia, hypertension, and impaired glucose tolerance are features of the metabolic syndrome [6]. Although, obesity may lead to respiratory failure in patients with lung disease, the systemic and mechanical effects of obesity may produce respiratory failure even in patients with normal lungs [15, 16]. Moreover, obesity makes more likely the cardiovascular and metabolic complications that adversely affect the health of the lung patients and increase the difficulty in treatment [12]. The pulmonary physician's attempts to induce his patients to quit smoking may be thwarted by the patient's fear of becoming too fat [3]. Hence, it is important for the respiratory physician to appreciate the risks of obesity, understand the active role that the adipose tissue has on health, and to treat obesity-related lung disease as a manifestation of a systemic disease by becoming familiar with the available methods: diet, drugs, and surgery for weight loss [17]. The relationship of body weight and pulmonary disease can be quite complex. While obesity in general has a negative effect on long-term survival, being overweight may benefit patients acutely in the ICU [18, 19]. Moreover, in addition, some lung diseases themselves, such as, COPD and lung cancer are associated with under nutrition and loss of muscle tissue, which have a detrimental effect on survival [20-22]. Hence, the treatment of obesity in these patients must be carefully carried out so that excess adipose tissue is lost, but not muscle strength, or endurance. One of the important areas of research is the diagnosis of obesity. Although now commonly defined by the BMI (weight in kilograms/ height in meters squared), it is clear that there are health consequences to body fat distribution, and waist, hip, and neck circumference may also be important in determining the effects of obesity [23, 24]. In addition, because BMI reflects both fat and muscle mass, evaluation of weight changes and loss may require measurement of muscle mass as well as BMI [21]. As we learn more about obesity and its effects, it becomes increasingly clearer that obesity related lung diseases need a coordinated multi-disciplinary approach to diagnosis and treatment. REFERENCES [1] Hedley AA, Ogden CL, Johnson CL, et al. Prevalence of overweight and obesity among US children, adolescents, and adults, 1999-2002. JAMA 2004; 291: 2847-2850. [2] Pi-Sunyer FX. The obesity epidemic: pathophysiology and consequences of obesity. Obes Res 2002; 10 Suppl 2: p. 97S-104S. [3] Klesges RC, Ward KD, Ray JW, Cutter G, Jacobs, Wagenknecht LE. The prospective relationship between smoking and weight in a young, biracial cohort: The Coronary Artery Risk Development in Young Adults Study. J Consult Clin Psychol 1998; 66: 487-93. [4] O'Hara P, Connett JE, Lee WW, Nides M, Murray R, Wise R. Early and late weight gain following smoking cessation in the Lung Health Study. Am J Epidemiol 1998; 148: 821-30. [5] Bjorntorp P. The associations between obesity, adipose tissue distribution and disease. Acta Med Scand Suppl 1998; 723: 121-34. [6] Pi-Sunyer X. The metabolic syndrome: how to approach differing definitions. Med Clin North Am 2007; 91: 1025-40. [7] Koziel S, Ulijaszek SJ, Szklarska A, et al. The effects of fatness and fat distribution on respiratory functions Annals of Human Biology 2007; 34(1): 123-131.