PAPER Obesity: the Disease of the Twenty-ﬁrst Century

Home , Obesity

International Journal of Obesity (2002) 26, Suppl 4, S2–S4 ß 2002 Nature Publishing Group All rights reserved 0307–0565/02 $25.00 www.nature.com/ijo PAPER Obesity: the disease of the twenty-ﬁrst century

SRo¨ssner1*

1Obesity Unit, Huddinge University Hospital, Stockholm, Sweden

The prevalence of obesity is increasing globally, with nearly half a billion of the world’s population now considered to be overweight or obese. The obesity epidemic is related both to dietary factors and to an increasingly sedentary lifestyle. Obesity has signiﬁcant co-morbidities and these are associated with substantial health care and social costs. Of particular concern is the fact that obesity is increasing among children and adolescents. National health policymakers must take action to deal with the obesity problem. Prevention should be the primary target, but it is also important to develop strategies to treat those already affected with obesity. International Journal of Obesity (2002) 26, Suppl 4, S2 – S4. doi:10.1038/sj.ijo.0802209

Keywords: obesity epidemic; sedentary lifestyle; dietary fat; co-morbidities

Introduction predisposition, disruption in energy balance, and environ- The statistics on obesity are appalling, with nearly half a mental and social factors. The rapid increases in obesity, billion of the world’s population now considered to be however, cannot be related purely to genetic change as the overweight or obese. The problem does not only affect genetic pool changes slowly over thousands of years. In developed countries, as there is now a significant increase contrast, the environment has changed dramatically over in overweight and obesity throughout the developing world. the past few decades and it is this that accounts for the recent It is estimated that, at the beginning of this century, more rise in obesity. people will die from complications of overnutrition than of The classic Danish adoption studies demonstrate the starvation. Obesity is relatively common in Europe. Current extent to which obesity is genetically determined. These prevalence data from individual national studies collated by show, for example, a highly significant correlation between the International Obesity Task Force (IOTF) suggest that body weight class (thin, median, overweight or obese) of obesity ranges from 10 to 20% for men, and 10 to 25% for adoptees and body mass index (BMI) of biological parents women.1 Figure 1 shows the current level of obesity in but no correlation between body weight class of adoptees and European countries. BMI of adoptive parents.2 This suggests that genetic influ- However, this prevalence has increased by about 10 – 40% ences are important in determining body adiposity and that in the majority of European countries in the past 10 y. The childhood family environment alone has little effect. most dramatic increase has been in the UK, where it has Research continues into the genetics of obesity and an more than doubled since 1980. Figure 2 shows data from update of the human obesity gene map has been published.3 recent Scandinavian studies. In all age ranges and both A total of 360 genes involved in obesity have now been genders in all countries, the trend is towards an increase in identified, although some are thought to have only a very overweight and obesity. minor role. It has been suggested that as much as 50% of the varia- bility in bodyweight is governed by genetic factors. While Causes of obesity little can be done to modify genetic predisposition to weight Obesity is caused by a combination of both genetic and gain, this leaves a considerable proportion of weight varia- environmental influences. The three main factors are genetic bility open to behavioural modification. In terms of energy intake, dietary fat is the most important macronutrient culprit. Compared with protein and carbohydrate, fat provides a higher energy content per gram, it produces fewer satiety signals, it is less able to *Correspondence: S Rossner, Obesity Unit, Health Behaviour Research, Huddinge University Hospital, Stockholm S-141 86 Sweden. suppress hunger and it has a higher capacity for storage in E-mail: [email protected] the body. Obesity: the disease of the twenty-first century SRo¨ssner S3

Figure 3 Markers of inactivity related to obesity incidence. (Source: Prentice et al.4) Figure 1 Obesity levels (BMI > 30 kg=m2) among men and women in some European countries (Source: IOTF). sleep apnoea, musculoskeletal disorders and some cancers. Many of these health consequences of overweight and obe- Although dietary fat is important, the increase in obesity sity are discussed in more detail in later papers in this has occurred at a time when overall energy intake has symposium. The risk of death from all causes, cardiovascular stabilized or even slightly reduced. Modern sedentary life- disease, cancer and other diseases increases throughout the styles appear to be at least as important as diet in the range of moderate and severe overweight for both men and development of obesity. This is illustrated by a study that women in all age groups.5 shows how markers of inactivity, such as the number of cars Type 2 diabetes is the most obvious clinical problem. per household and the number of hours watching television Adults with a BMI 35 are approximately 20 times more each week, mirror the rise in obesity (Figure 3).4 In 1960, an likely to develop diabetes over a 10 y period than their peers average of 13 h=week was spent watching television com- with a BMI between 18.5 and 24.9.6 The prevalence of pared with 26 h=week today. diabetes is rising dramatically throughout the world. The Energy imbalance takes place slowly over a long time number of adults with diabetes is forecast to increase by 46% period. It is instructive to consider how modern technologies from 151 million in 2000 to 221 million in 20107,8 and can affect energy usage. For example, use of remote controls between 1995 and 2025, the number of individuals with type and mobile telephones could ‘save’ 25 h of walking each 2 diabetes could double globally. year. Assuming that 1 h of walking is equivalent to 113 – If, previously, health policymakers have seen obesity as a 226 kcal energy expenditure, this equates to an energy trivial, cosmetic complaint, the rapid increase in diabetes ‘saving’ over the year of 2800 – 6000 kcal, the equivalent of should act as an impetus for action. an additional 0.4 – 0.8 kg of adipose issue. The co-morbidities associated with obesity have considerable ﬁnancial costs. The IOTF has estimated the cost of obesity 1 Consequences and costs of obesity at between 2 and 8% of total health care budgets. These data are consistent in all parts of the world, irrespective of the Obesity is a risk factor for chronic diseases such as hyperten- health care system, and represent a heavy burden to society. sion, dyslipidaemia, type 2 diabetes, cardiovascular disease, However, the personal economic and social costs of obesity are also signiﬁcant in terms of reduced quality of life, low employment prospects, stigmatization and poor social inte- gration. One study showed that, compared with non-obese women, obese women were less likely to have married, had completed fewer years of education and had lower household income. Self-esteem was also lower.9

Obesity in children Of particular concern for the future is the alarming rise in obesity in children and adolescents; related to this, type 2 diabetes is occurring at increasingly younger ages. In 1999, the prevalence of obesity in 15 – 24 y-olds in Europe was Figure 2 Evolution of adult obesity in Scandinavia showing increasing reported to be as high as 8% in Ireland and 11% in levels of obesity in both sexes in all countries. Greece10 (Table 1). This increase is not only taking place in

International Journal of Obesity Obesity: the disease of the twenty-first century SRo¨ssner S4 Table 1 Prevalence of obesity (BMI > ciated co-morbidities have substantial health care and social 30 kg=m2)in15– 24 y-old Europeans. costs. Prevention must be our primary target, but it will also 10 Source: Martinez et al. be important to develop strategies to treat those already Country Percentage Obesity affected with obesity, as even modest weight loss of 5 – 10% has been shown to reverse many of the comorbidities asso- Italy 1.0 ciated with obesity and to result in significant health gains.12 Finland 1.2 Spain 1.4 Portugal 1.5 France 1.8 References Sweden 2.0 1 International Obesity Task Force.www.obesite.chaire.ulaval.ca= Denmark 2.5 iotf.htm. Germany 3.0 2 Stunkard AJ, Sorensen TI, Hanis C, Teasdale TW, Chakraborty R, Luxembourg 3.3 Schull WJ, Schulsinger F. An adoption study of human obesity. UK 3.5 New Engl J Med 1986; 23: 193 – 198. Belgium 4.1 3 Rankinen T, Perusse L, Weisnagel SJ, Snyder EE, Chagnon YC, Netherlands 4.8 Bouchard C. The human obesity gene map: the 2001 update. Obes Austria 5.2 Res 2002; 10: 196 – 243. Ireland 8.0 4 Prentice AM, Jebb SA. Obesity in Britain: gluttony or sloth? Br Med Greece 11.0 J 1995; 311: 437 – 439. 5 Calle EE, Thun, MJ, Petrelli JM, Rodriguez C, Heath CW. Body- mass index and mortality in a prospective cohort of US adults. New Engl J Med 1999; 341: 1097 – 1105. 6 Field AE, Coakley EH, Must A, Spadano JL, Laird N, Dietz WH, the Westernized countries. In Japan, for example, where Rimm E, Colditz GA. Impact of overweight on the risk of devel- obesity was unheard of 20 y ago, childhood obesity is now oping common chronic diseases during a 10-year period. Arch becoming a major issue, and the incidence of type 2 diabetes Intern Med 2001; 161: 1581 – 1586. in junior high school Japanese children rose from 8 7 Zimmet P, Alberti KG, Shaw J. Global and societal implications of the diabetes epidemic. Nature 2001; 414: 782 – 787. cases=100 000 in 1976 – 1980 to more than 14 cases=100 000 8 King H, Aubert RE, Herman WH. Global burden of diabetes, 11 in 1991 – 1995. 1995 – 2025: prevalence, numerical estimates, and projections. Prevention of obesity has to start in these younger age Diabet Care 1998; 21: 1414 – 1431. groups, and should focus on simple measures such as 9 Gortmaker SL, Must A, Perrin JM, Sobol AM, Dietz WH. Social and eonomic consequences of overweight in adolescence and young encouraging adoption of a healthy diet and promoting a adulthood. New Engl J Med 1993; 329: 1008 – 1012. non-sedentary lifestyle, particularly by encouraging physical 10 Martinez JA, Kearney JM, Kafatos A, Paquet S, Martinez-Gonzalez activity within schools. MA. Variables independently associated with self-reported obesity in the European Union. Publ Health Nutr 1999; 2: 125 – 133. 11 American Diabetes Association. Consensus statement on type 2 Summary diabetes in children and adolescents. Diabet Care 2000; 22: 381. 12 Royal College of Physicians of London. Clinical management of In summary, there is a significant global increase in the overweight and obese patients with particular reference to the use of prevalence of overweight and obesity. Obesity and its asso- drugs. RCP: London; 1998.

International Journal of Obesity