CTF Structured Abstract: Obesity

Canadian Task Force on Preventive Health Care

Structured Abstract

Please note: In 2003, the CTF updated its Grades of Recommendations to include an "I Recommendation" for situations where insufficient evidence exists to allow a recommendation to be made. (Formerly, these situations were captured under a "C Recommendation".) This change is not retroactive, and all "C Recommendations" made prior to 2003 have not been reevaluated in light of the new "I" recommendation grade. For a discussion of these recommendation grades, please link to the 2003 article in the Canadian Medical Association Journal here.

Periodic health examination, 1999 update: 1. Detection, prevention and treatment of obesity

Prepared by James D. Douketis, MD and John Attia, MD, PhD, Department of Medicine, McMaster University, Hamilton, Ont.; John W. Feightner, MD, Department of Family and Community Medicine, University of Western Ontario, London, Ont.; William F. Feldman, MD, Department of Pediatrics, University of Toronto, Toronto, Ont.; with the Canadian Task Force on Preventive Health Care

These recommendations were finalized by the Task Force in January 1998 and published in the Canadian Medical Association Journal February 23, 1999 (CMAJ 1999; 160(4) ).

Objective
Burden of Suffering
Options
Outcomes

Evidence
Values
Benefits, Harms, and Costs

Recommendations
Validation
Sponsors

Objective

(1) To evaluate the evidence relating to the effectiveness of methods to prevent and treat obesity, and (2) to provide recommendations for the prevention and treatment of obesity in adults aged 18 to 65 years and for the measurement of the body mass index (BMI) as part of a periodic health examination.

Burden of Suffering

Obesity (BMI > 27) is a highly prevalent condition that affects 35% of men and 27% of women in Canada, while morbid obesity (BMI > 35) is found in 2% of men and 4% of women. Obesity is associated with the development of several diseases, including hypertension, diabetes mellitus, hyperlipidemia, coronary artery disease, obstructive sleep apnea, and cancers of the breast, uterus, prostate and colon. It is also associated with psychological disorders, including depression, anorexia nervosa and bulimia, and is an independent risk factor for increased mortality.

Options

In adults with obesity (BMI greater than 27) management options include weight reduction, prevention of further weight gain or no intervention.

Outcomes

The long-term (more than 2 years) effectiveness of (a) methods to prevent obesity and (b) methods to treat obesity.

Evidence

MEDLINE was searched for articles published from 1966 to April 1998 that related to the prevention and treatment of obesity. The key words used for the search were "obesity" and "body mass index," and the MeSH terms used were "diet therapy," "drug therapy," "prevention and control," "surgery" and "therapy." Additional articles were identified from the bibliographies of review articles and the listings of Current Contents. Selection criteria were used to limit the analysis to prospective studies with at least 2 years' follow-up.

Recommendations were graded as:

A Good evidence to support the recommendation that the condition be specifically considered in a PHE.

B Fair evidence to support the recommendation that the condition be specifically considered in a PHE.

C Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.

D Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

E Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

Quality of evidence was rated according to 5 levels:

I Evidence from at least 1 properly randomized controlled trial (RCT).

II-1 Evidence from well-designed controlled trials without randomization.

II-2 Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.

II-3 Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.

III Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.

Values

The Task Force of experts in family medicine, internal medicine, pediatrics, psychiatry, surgery and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions. Recommendations were not based on cost-effectiveness of options. Patient preferences were not discussed.

Background papers providing critical appraisal of the evidence and tentative recommendations prepared by the chapter author were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in several 1- to 2-day meetings in 1994. An update of the review was completed in 1997 and reviewed by the Task Force via in January and June 1997. Consensus was reached on recommendations, which were finalized in June 1998.

Benefits, Harms, and Costs

Studies investigating the effect of dietary therapy on obesity often find initial weight reductions which are followed by gradual weight regain. Very-low-calorie diets have been associated with fatigue, dizziness, hair loss, menstrual irregularities, cholelithiasis, gouty arthritis and cardiac arrhythmias. A similar reduction-regain pattern is observed with anoretic drug therapy, with effective weight loss during the first six months of treatment, while the effectiveness beyond 1 year has only been shown in a small proportion of patients from a single study. Anorectic drug therapy is associated with drowsiness, fatigue, nausea, diarrhea, urinary retention, dry mouth and a small but clinically important increased risk of pulmonary hypertension and valvular heart disease. Long-term success has been reported in a number of studies investigating weight-reduction surgery. Postoperative morbidity occurred in less than 5% of patients in the studies reviewed, with re-operative rates reported from 1.7% to 7.1% in 3 studies and 20.3% to 33.3% in 2 others. Long-term dietary counselling has been shown to be successful in a small proportion of patients who achieved sustainable moderate weight-loss.

Also, weight-reduction interventions are associated with an increased risk of major depression, bulimia and other eating disorders. Despite earlier concerns about the risks associated with repeated episodes of weight loss and weight regain (weight cycling), recent reviews have found that weight cycling is not associated with increased mortality.

Recommendations

Recommendation grade [A, B, C, D, E] and level of evidence [I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations in support of individual recommendations are identified in the guideline text.

Prevention:

There is insufficient evidence to recommend in favour of or against community-based obesity prevention programs; however, because of considerable health risks associated with obesity and the limited long-term effectiveness of weight-reduction methods, the prevention of obesity should be a high priority for health care providers [C, II-1].

Treatment:

(a) For obese adults without obesity-related diseases, there is insufficient evidence to recommend in favour of or against weight-reduction therapy because of a lack of evidence supporting the long-term effectiveness of weight-reduction methods [C, I, II-1, II-2];
(b) for obese adults with obesity-related diseases (e.g., diabetes mellitus, hypertension), weight reduction is recommended because it can alleviate symptoms and reduce drug therapy requirements, at least in the short term [B, I, II-1]

Detection:

(a) for people without obesity-related diseases, there is insufficient evidence to recommend the inclusion or exclusion of BMI measurement as part of a periodic health examination, and therefore BMI measurement is left to the discretion of individual health care providers [C, II-2];
(b) for people with obesity-related diseases, BMI measurement is recommended because weight reduction should be considered with a BMI of more than 27 [B, I, II-2].

Validation

This report was externally peer reviewed. To address the importance of obesity as a public health issue, the Canadian Guidelines for Healthy Weights and the Report of the Task Force on the Treatment of Obesity were published in 1988 and 1991 respectively. Both reports recognized that men and women with obesity are at increased risk for health-related problems and recommended interventions for the prevention and treatment of obesity. Although these reports provided useful treatment guidelines, emphasis was placed on the need to regulate dietary methods of treatment, particularly commercially available diets. Weight-reduction methods also include pharmacologic, surgical and behavioural treatments.

A	Good evidence to support the recommendation that the condition be specifically considered in a PHE.
B	Fair evidence to support the recommendation that the condition be specifically considered in a PHE.
C	Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.
D	Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.
E	Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

I	Evidence from at least 1 properly randomized controlled trial (RCT).
II-1	Evidence from well-designed controlled trials without randomization.
II-2	Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.
II-3	Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.
III	Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.