Call for action: preventing and managing the expansive and expensive obesity epidemic

David C.W. Lau, MD, PhD

CMAJ 1999;160:503-5

Reprint requests to: Dr. David C.W. Lau, Division of Endocrinology and Metabolism, Ottawa Hospital — Civic Campus, 1053 Carling Ave., Ottawa ON K1Y 4E9; fax 613 761-5358; lau@civich.ottawa.on.ca

© 1999 Canadian Medical Association

• Letter: Understanding obesity
• Evidence: The cost of obesity in Canada
• Education: Periodic health examination, 1999 update: 1. Detection, prevention and treatment of obesity

The recognition that obesity represents a rapidly growing health threat worldwide led to the formation of the International Obesity Task Force, whose mandate was to develop a public health policy and program for improving the prevention and management of obesity. The comprehensive report by the task force was released in the fall of 1998⁵ and has been endorsed by the World Health Organization (WHO). The WHO and the International Association for the Study of Obesity are working with the national obesity associations in various countries to help implement the report and, more important, to persuade health policy-makers and key health professional organizations to recognize obesity as a disease that requires urgent action.

Developing strategies for the prevention and management of obesity requires a systematic approach that includes the following steps: defining the problem of obesity, establishing associated health risks, determining the benefits and risks associated with weight reduction, estimating the economic cost of obesity and outlining the principles of prevention and management of obesity in at-risk individuals and populations. The growing problem of obesity and the increased health risks attributable to obesity are well established^6­8 and were reaffirmed in the Canadian Heart Health Surveys.³ In the group surveyed who were 18 to 54 years old, for example, the prevalence rates of dyslipidemia, hypertension and self-reported diabetes were 2- to 10-fold higher among people with a body mass index (BMI) of 30 or greater than among those with the lowest BMI.⁹

In this issue, 2 articles address the other relevant steps toward developing prevention and management strategies. In the first article Dr. C. Laird Birmingham and associates provide an estimate of the direct cost of obesity in Canada (page 483).¹⁰ In the other article Dr. James D. Douketis and colleagues, with the Canadian Task Force on Preventive Health Care, examine the use of the BMI as a measurement of obesity and make recommendations on the prevention and treatment of obesity (page 513).¹¹ Their review of the evidence is important because the data concerning the health benefits and risks of weight reduction are less robust and require closer scrutiny. Both papers underscore the need to develop sound and rational strategies for implementing a systematic approach to tackle the growing problem of obesity in Canada.

In addition to the disease burden of obesity on affected individuals and their families, the economic costs of obesity are high, ranging from 2%­10% of the total health care budgets of different countries.^12­14 For the first time we have a realistic estimate of the direct cost of obesity in Canada: about $2 billion per annum, or 2.4% of the total health care budget.¹⁰ By using the prevalent-based approach in their cost-of-illness study, Birmingham and associates may have underestimated the age- and sex-specific incidence of disease attributable to a chronic disease like obesity. Moreover, they did not include all of the diseases attributable to obesity in their analysis, which may further underestimate the real cost. Nevertheless, their estimated direct cost of obesity in Canada is similar to figures obtained for New Zealand, Australia and France but somewhat lower than those for Germany, the United States and Sweden.¹⁴ The high cost should provide incentives to all physicians and health care professionals, not just obesity specialists and researchers, to prevent and manage this prevalent disease. It follows from this paper that there is a call for more data on the quality of life and the treatment benefits by means of cost-benefit and cost-utility analyses.

Obesity is characterized by excessive body fat accumulation in adipose tissue to an extent that health may be adversely affected. Defining obesity without standardized methodology has been a challenge. A standardized measure of body fat and its distribution and the classification of obesity will allow for more accurate estimates of prevalence rates of obesity in the population, the identification of individuals or groups at increased health risks, the identification of priorities for intervention at the individual and community levels and, more important, the evaluation of intervention and treatment strategies.

The BMI is a simple index of weight to height that provides the best anthropometric measure of body adiposity. Canada adopted the use of the BMI for guidelines for healthy weights in 1988 and was one of the first countries to do so.¹⁵ A BMI of 20­25 is considered a good value for most people, whereas a BMI above 25 is associated with an increasing risk of health problems.¹⁵ The WHO consultation report currently defines overweight as a BMI of 25 or greater and obesity as a BMI of 30 or greater. Obesity can be further classified as moderate (class I, BMI 30­34.9), severe (class II, BMI 35­39.9) or very severe (class III, BMI 40 or greater).⁵

Because the BMI does not take into account the distribution of fat and the associated health consequences that vary considerably among individuals, additional markers are needed to complement BMI in assessing health risks. Indeed, recent studies suggest that obesity-related comorbidities are better correlated with the presence of upper-body or abdominal fat distribution and are independent of the degree of excess fat.^6,8,16­19

Douketis and colleagues conclude from their extensive literature search that there is insufficient evidence to recommend the inclusion or exclusion of BMI measurement for the general population as part of the periodic health examination; instead they recommend that BMI measurement be left to the discretion of individual health care providers. The authors, however, do recommend BMI measurement in people with obesity-related comorbidities. The importance of fat distribution in assessing health risks was acknowledged, but no recommendations were made because of lack of available standardized indices.

With respect to the prevention and treatment of obesity, Douketis and colleagues believe that this should be a priority for health care providers. They recommend weight reduction for obese adults with obesity-related comorbidities such as diabetes mellitus and hypertension, but they could not recommend for or against treatment of obesity in adults without obesity-related comorbidities because of a lack of evidence supporting the long-term effectiveness of weight-reduction methods.

The recommendations by Douketis and colleagues are consistent with those of a much more comprehensive evidence-based report recently published by the National Institutes of Health,²⁰ with 3 notable exceptions. First, the US expert panel recommended that BMI be measured in adults to classify overweight and obesity and to estimate relative risk of disease compared with normal weight. This makes sense because health care professionals are notoriously poor in estimating overweight and obesity by visual inspection alone. Furthermore, the BMI can easily be deduced using normograms or tables from height and weight measurements, both of which are part of the periodic health examination. Second, the US panel recommended that waist circumference be included to assess abdominal fat content given the compelling data correlating abdominal fat to obesity-related comorbidities.^6,16,17,19 People could be classified as high risk with the use of waist-circumference cutoffs of more than 40 inches (102 cm) and more than 35 inches (88 cm) for men and women respectively. Finally, the US panel recommended treatment for overweight patients if they have 2 or more obesity-related comorbidities or risk factors.²⁰

Obesity is a complex chronic disease with diverse multifactorial etiology. Minimalists attribute the rising prevalence of obesity largely to physical inactivity and ready access to highly palatable foods with a high fat content. Current research aims to uncover how and why obesity develops, the comprehensive understanding on which successful treatment rests. The intensive search for the genes responsible for obesity has led to a steady increase in the number of putative genes or loci linked to, or associated with, obesity. The number is currently approaching 200, with loci mapped in all but the Y chromosomes.²¹ However, single genetic mutations are rare causes of human obesity. To date, there are only 25 reported cases of obesity resulting from 11 single mutations in 7 genes,^22­29 an increase from 3 cases reported in 1997.³⁰ Hence, emerging data suggest that multiple genes are more likely involved in human obesity, in contrast to the widely studied rodent models of obesity, where single gene mutations are the rule.³¹

Because genetic heritability accounts for only 25%­30% of the obesity phenotype,³² prevention and treatment should logically be directed mainly at environmental factors (social, behavioural and cultural) as principal determinants. Modification of behaviours and lifestyle habits remains the cornerstone treatment of obesity. Earlier data suggest that the effectiveness of weight-reduction methods is rather limited. This is true if the primary outcome is body weight rather than improved health status. The overall goal for obesity management is to reduce the health risks, which begin to lessen even with modest weight loss, long before a desirable body weight is achieved. Recent evidence indicates that even a modest loss can alleviate symptoms of obesity-related comorbidities.^33,34

Obtaining a desirable body weight often proves difficult and elusive. The initial goal is to reduce body weight by approximately 10% from baseline over 6 to 12 months. In terms of strategies for weight loss and weight maintenance, the most successful treatment to date includes a controlled diet with a deficit of 500­1000 kcal (2100­4200 kJ) per day, with reduced dietary fat intake of less than 30% of total energy intake, regular physical activity programs and reinforcement of behavioural modification techniques. The extensive review by Douketis and colleagues¹¹ on the effectiveness of obesity treatment ignored the benefits of regular physical activity when incorporated as an integral component of a weight-reduction program. When coupled with a judicious controlled diet, exercise accelerates fat loss while maintaining lean body mass, and it helps to sustain weight loss over the long term.^35,36 Indeed, healthy lifestyle measures incorporating both diet and regular physical activity have been shown to significantly delay the onset or prevent the development of type 2 diabetes in obese and nonobese subjects.^37,38

Pharmacotherapy can be useful as an adjunct to controlled diet and physical activity for people with a BMI of 30 or greater with no concomitant risk factors and for those with a BMI of 27 or greater with concomitant risk factors or diseases.³⁹ Two drugs with novel modes of action and known efficacy in long-term studies will soon be available in Canada: sibutramine, an appetite suppressant that specifically inhibits norepinephrine and serotonin reuptake,⁴⁰ and orlistat, which is a pancreatic lipase inhibitor that reduces fat absorption.⁴¹ Sibutramine, unlike dexfenfluramine or fenfluramine, is not associated with primary pulmonary hypertension or heart valve abnormalities.⁴² The availability of these drugs will be a welcome addition to the armamentarium in long-term obesity management.

Other obesity treatment options include bariatric surgery, which is usually reserved for people with class 3 obesity (BMI of 40 or greater). The large prospective randomized Swedish Obesity Study, still under way, has provided encouraging interim data to suggest that weight reduction following bariatric surgery reduces the 2-year incidence of diabetes, hypertension and other health risks by 3- to 32-fold.⁴³

Because of the limited success of current obesity treatments, the challenges as we approach the new millennium will be to understand how obesity develops and to design strategies targeting the undesirable societal, cultural and other environmental influences. Different levels of preventive action can be undertaken: universal or public health prevention directed at the entire population, selective prevention directed at groups at risk, and targeted prevention directed at individuals at high risk and those who are overweight but not obese.

Enhancing the knowledge and attitudes of health care professionals about obesity is equally important. The acceptance of obesity as a medical disease with increased morbidity and mortality should supplant the previous prevailing perception of obesity as a cosmetic concern. Promoting healthy eating habits and increased physical activity are clearly priorities that should be established with active participation from governments, the private business sector, the media and, above all, consumers. This will provide an excellent opportunity for synergism of government public health policies directed at improving health. There is a call for action to form an obesity network in Canada to develop and implement effective programs and policies in the prevention and treatment of the growing epidemic of obesity in this country.

Competing interests: None declared.

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