Table 2.

Evidence classification and recommendation strength schemes based on the Obesity Canada methodology [18, 21]

Evidence classification scheme  Level 1a: evidence from meta-analysis of RCTs  Level 1b: evidence from at least 1 RCT  Level 2a: evidence from at least 1 controlled study without randomization  Level 3: evidence from non-experimental descriptive studies, such as comparative studies, correlation studies, and case-control studies  Level 4: evidence from expert committee reports or opinions or clinical experience of respected authorities, or both

Recommendation strength  Grade A: directly based on level 1 evidence  Grade B: directly based on level 2 evidence or extrapolated recommendation from category 1 evidence  Grade C: directly based on level 3 evidence or extrapolated recommendation from level 1 or 2 evidence  Grade D: directly based on level 4 evidence or extrapolated recommendation from level 1, 2, or 3 evidence