Obesity is now reaching epidemic proportions in both developed and developing countries and is affecting not only adults but also children and adolescents. Over the last 20 years, obesity has become the most prevalent nutritional problem in the world, eclipsing undernutrition and infectious disease as the most significant contributor to ill health and mortality. It is a key risk factor for many chronic and noncommunicable diseases.
In Canada, the prevalence of overweight and obesity has increased over recent decades among both children and adults in all areas of the country. According to the most recent estimates from the 2004 Canadian Community Health Survey,1 59% of the adult population is overweight (i.e., body mass index [BMI] ≥ 25 kg/m2) and 1 in 4 (23%) is obese (i.e., BMI ≥ 30 kg/m2). The sheer numbers of people who are overweight and obese highlight a pressing public health problem that shows no signs of improving in the near future. What is more alarming is the problem of obesity among children and adolescents in Canada, which is advancing at an even more rapid pace than obesity among adults. In 2004, 1 in 4 (26%) Canadian children and adolescents aged 2–17 years was overweight. The obesity rate has increased dramatically in the last 15 years: from 2% to 10% among boys and from 2% to 9% among girls.1,2 This increase is cause for concern, since there is a tendency for obese children to remain obese as adults. Moreover, obesity-related health problems are now occurring at a much earlier age and continue to progress into adulthood. Given the recent temporal obesity trends among children and youth, the prevalence of obesity among adults will likely continue to increase as the current generation of children enters adulthood.
Obesity should no longer be viewed as a cosmetic or body-image issue. There is compelling evidence that overweight people are at increased risk of a variety of health problems, including type 2 diabetes, hypertension, dyslipidemia, coronary artery disease, stroke, osteoarthritis and certain forms of cancers. It has recently been estimated that about 1 in 10 premature deaths among Canadian adults 20–64 years of age is directly attributable to overweight and obesity. In addition to affecting personal health, the increased health risks translate into an increased burden on the health care system. The cost of obesity in Canada has been conservatively estimated to be $2 billion a year or 2.4% of total health care expenditures in 1997.3 Thus, the continuing epidemic of obesity in Canada is exacting a high toll on the health of the population.
The cause of obesity is complex and multifactorial. Within the context of environmental, social and genetic factors, at the simplest level obesity results from long-term positive energy balance — the interaction of energy intake and energy expenditure. The rapid increase in the prevalence of obesity over the past 20 years is a result of environmental and cultural influences rather than genetic factors. With progressive improvements in the standard of living in developed and developing countries, overnutrition and sedentary lifestyle have supplanted physical labour and regular physical activity, which has resulted in positive energy balance and overweight.
Considerable advances have been made in dietary, exercise, behavioural, pharmacologic and bariatric surgical approaches to successful long-term management of obesity. Lifestyle interventions remain the cornerstone of the treatment of obesity, but adherence is poor and long-term success is modest because of significant barriers both on the part of affected individuals and health care professionals responsible for the treatment. Pharmacotherapy and bariatric surgery are useful adjuncts for improving the health outcomes of overweight people, but, for a variety of reasons, these modalities of treatment are not widely adopted.
Despite steady progress in the management of obesity, its prevalence continues to rise. To date, population interventions have tended to focus on individual risk factors and have been largely ineffective. Hence, sweeping prevention and intervention strategies are required to slow, and hopefully reverse, the alarming increase in obesity prevalence in Canada and globally.
A number of clinical practice guidelines on the assessment and management of obesity have been published in the past. These have been largely based on consensus statements by expert panels. Moreover, most of these guidelines focus on individuals rather than on communities and the population as a whole. Recognizing these deficiencies, Obesity Canada — a not-for-profit organization founded in 1999 to improve the health of Canadians by decreasing the occurrence of obesity — convened a panel of experts to determine whether a comprehensive set of guidelines could be developed to address not only the management but also the prevention of obesity in both adults and children. Members of the Steering Committee and Expert Panel unanimously agreed on an evidence-based approach. Through the process of developing these guidelines, which began in the spring of 2004, members of the Steering Committee and Expert Panel identified major gaps in knowledge regarding obesity treatment and prevention. Considerable research is required in many areas to optimize management and to prevent the increasing prevalence of overweight and obesity in Canada. The authors' recommendations range from the need for enhanced surveillance and population-based data to new research on the biological, social, cultural and environmental determinants of obesity as well as research on effective treatment strategies, policies and interventions.
Because obesity is increasingly viewed as a societal issue, members of the Steering Committee and Expert Panel unanimously agreed to include chapters on the prevention of obesity in children and adults at the population level, as well as implications of the guidelines for health policy-makers and other interested parties.
The challenges of disseminating and implementing these guidelines were acknowledged by the Steering Committee, and a dissemination strategy has been developed to ensure that they are translated into clinical practice.
Publication of these guidelines is not the end of this process; it is only the beginning. Ongoing evaluation and revision of the various chapters and recommendations will be undertaken, as appropriate. It is hoped that, with continuing new knowledge from research, regular updating of these guidelines will accord greater certainty to many of the recommendations and expected outcomes.