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
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.
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 neenassociated 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 inless than 5% of patients
in the studies reviewed, with reoperative 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 proporting 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 examiantion, 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.
Sponsors
The Canadian Task Force on Preventive Health
Care developed this guideline with funding from the Provincial and
Territorial Ministries of Health and Health Canada.