Introduction
Obesity is one of the major public health challenges of our time.1, ∗2, 3 Although the causes for the marked increases in obesity over the last 30 years are incompletely understood, ecological models plausibly sketch how technological, economic, and ultimately social changes have created an environment (“obesogenic environment”) conducive to weight gain.4 From an economic point of view, these environmental changes have altered the opportunity cost for behaviors related to energy intake (dietary behavior) and energy expenditure (physical activity),5 promoting a positive energy balance and subsequent weight gain in broad segments of the population.∗4, 5, 6 The most widely used measure in population based health research, is the body mass index (BMI = kg/m2).1, 3, 7 According to the World Health Organization (WHO), overweight is defined as 25 kg/m2 ≤ BMI < 30 kg/m2, and obesity as BMI ≥ 30 kg/m2.7 Obesity may further be subdivided into moderate (class I) obesity: 30 kg/m2 ≤ BMI < 35 kg/m2, severe (class II) obesity: 35 kg/m2 ≤ BMI < 40 kg/m2, and morbid (class III) obesity: BMI ≥ 40 kg/m2.
Globally, overweight and obesity have considerably increased since the early 1980s.3 In 2008, about one-third of the world's adult population (∼1.46 billion) was overweight, whereas the age-standardized prevalence of obesity was 9.8% in men and 13.8% in women; with wide variation between and within countries.3 Particularly affected are the USA, where 35.5% of men and 35.8% of women were classified as obese in 2010.3, ∗8 These increases pose large problems for healthcare systems worldwide, since obesity constitutes a serious risk factor for a plethora of health problems.9, 10 While some are simply a consequence of the physical burden of the excess adipose tissue itself (e.g. aches and pains, dyspnea, sleep disturbances), the majority of obesity-related medical conditions result from serious endocrine and metabolic changes (e.g. diabetes mellitus type 2, cardiovascular disease, increased cancer risk).10 As a result, obesity is inversely associated with a multitude of health-related outcomes.11, 12 Research has shown that obese persons enjoy a lower quality of life,13 possess more functional limitations,14 and have a reduced life expectancy.15 Because of the large number of diseases excess-weight may bring about, obese persons use considerably more healthcare services.16, 17 Against this background obesity must be expected to negatively impact economic outcomes as well.∗18, 19
Based upon available literature reviews, augmented with exemplary original research articles, the present study provides an overview of selected economic outcomes associated with overweight and obesity. Section two gives a brief introduction to basic concepts of cost of illness (COI) studies, in which concepts and terms, referred to throughout the remainder of this article, will be introduced. Sections three and four cover the economic impact of excess-weight in adults (in terms of direct and indirect costs), while section five is dedicated to economic consequences of overweight and obesity in children and adolescents. The article closes with a short summary and some recommendations for further research.