CTF Structured Abstract: Prevention of Obesity in Adults

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.

Prevention of Obesity in Adults

Prepared by James Douketis, MD, Clinical Research Fellow in Thromboembolism, Department of Medicine, McMaster University and William Feldman, MD, FRCPC, Professor of Pediatrics and of Preventive Medicine and Biostatistics, University of Toronto, Ontario

These recommendations were finalized by the Task Force in January 1994

Objective
Burden of Suffering
Options
Outcomes

Evidence
Values
Benefits, Harms, and Costs
Recommendations

Validation
Sponsors
Selected References

Objective

To make recommendations about preventing obesity in adults (18 to 65 y) in Canada.

Burden of Suffering

In a cross-sectional study conducted between 1986-1990 in Canadians aged 18-74, the prevalence of obesity (BMI ł 27 kg/m²) was 35% in men and 27% in women. Three percent of men and 5% of women were found to be morbidly obese (BMI ł 35 kg/m²). Factors associated with an increased prevalence of obesity include increased age, a low level of education, low physical activity, alcohol use in men and parity in women. Obesity has been causally linked to several diseases including coronary artery disease, hypertension, hyperlipidemia and diabetes. The psychological impact of obesity, although not as well studied, may be substantial, given the emphasis on a lean body image and the negative perception of an overweight state that currently exist in our society.

Options

Main preventive strategies were counselling and routine measurement of body mass index (BMI) (weight/height²). Other preventive and treatment strategies were community-based educational programs, dietary therapy (calorie-restricted diets), appetite suppressant drug therapy, behaviour therapy, surgery (vertical band gastroplasty, intragastric balloon insertion) and exercise.

Outcomes

Weight loss, recidivism.

Evidence

MEDLINE was searched for the years 1966 to June 1993 using the keywords obesity and weight reduction. Other data sources included bibliographies of review articles and recently published articles. Study results were synthesized in table or graphic format only.

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 13-member Task Force of experts in family medicine, geriatric medicine, pediatrics, psychiatry 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 1- to 2-day meetings, 2 to 3 times per year from January 1993 to June 1993. Consensus was reached on final recommendations.

Benefits, Harms, and Costs

BMI is a reliable, easy measure, and correlates well with body fat content.

Evidence from RCTs and prospective cohort studies suggests that weight reduction in obese persons can lead to improvements in existing conditions such as diabetes, hypertension, hyperlipidemia and obstructive sleep apnea. Little evidence exists that treatment of obesity will prevent myocardial infarction, stroke or diabetes, or reduce mortality (p578).

2 large community-based cohort studies examined the effects of educational programs on weight loss. No significant differences in average weight loss were found 5 to 10 years post-intervention for communities who received and did not receive education.

Randomized controlled trials and cohort studies report that low calorie diets (1000 to 1500 kcal/day) and very low calorie diets (<800 kcal/day) result in weight reductions in the short-term. However, most patients returned to their pre-treatment weight within 1 to 5 years (576). Similar results were reported for appetite-suppressant drug therapy as an adjunct to dietary therapy. Behavioural therapy can result in modest weight losses (i.e., 0.5 to 0.75 kg/week), but again most losses are not sustained over the long term (p577). Lumen-reducing surgical procedures are usually considered only for persons with morbid obesity who have not responded to more conservative treatment. A small cohort study examining vertical band gastroplasty reported reduced mortality for selected patients. A placebo-controlled study found no significant difference in weight loss for patients treated with intragastric balloon inflation and those treated with dietary therapy (p577). There is little evidence that exercise combined with dietary and behavioural strategies augments weight loss unless there is a significant change in baseline exercise capacity.

Potential adverse effects vary by treatment. Diets of <1000 kcal can cause orthostatic hypotension, fatigue, hair loss, menstrual irregularities and symptomatic cholelithiasis. Adverse effects of drug therapy include drowsiness, fatigue and gastrointestinal discomfort. Surgical interventions can result in gastric ulceration, perforation and bowel obstruction. Observational studies suggest that weight reductions and fluctuations may lead to increased mortality and cardiovascular morbidity.

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.

*Note: These recommendations have been updated.
Link to recommendation table for 1999 update: Detection, prevention and treatment of obesity

Insufficient evidence exists to recommend for or against counselling (during the PHE) to prevent obesity in adults [C, II-2].
Insufficient evidence exists to include or exclude (from the PHE) routine measurement of height and weight, BMI or treatment of obesity [C, I, II-2]. Weight reduction may be "cautiously recommended" for persons with coexisting diabetes, hypertension or hyperlipidemia. For persons who are obese or in the upper-normal BMI range who are not candidates for weight reduction, or who have been unsuccessful at weight reduction, maintenance of a stable weight is a reasonable alternative.

Validation

This report was externally peer reviewed. The 1990 Canadian Task Force on the Treatment of Obesity recommended weight loss for persons with coexisting conditions that could be ameliorated with weight loss and/or those at risk for developing obesity-related conditions. In addition to this, the U.S. National Institute of Health Technology Assessment Conference on Obesity also suggested weight loss for persons near the upper limit of the healthy weight range.

Selected References

Source Document

Douketis J. and Feldman W. Prevention of obesity in adults. In: Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994; 574-84.

Link to Full Text of this review

Link to Summary Table of Recommendations of this review

Link to Selected References list of this review

Link to 1999 update: Detection, prevention and treatment of obesity

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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.