Thirty-nine studies were included in the analysis; 3 prospective cohort studies investigated the effectiveness of obesity prevention (6,779 intervention and 6,314 control), and 36 investigated the effectiveness of weight-reduction interventions (14 dietary (8 RCTs and 6 prospective cohort) with 1,248 participants), 8 RCTs on anorectic drug therapy with 2,035 participants, 9 dietary counselling or behavioural therapy (5 RCTs and 4 prospective cohort) with 5,002 participants, and 5 surgical (4 RCTs and 1 prospective cohort) with 650 participants).
There was moderate to high inter-rater agreement in the selection of studies (k value 0.70) and data extraction (k value 0.66).
Prevention: There is insufficient evidence to recommend in favour of or against community-based obesity prevention programmes; 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 (grade C recommendation).
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 (grade C recommendation).
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 (grade B recommendation).