Table 2

National Institutes of Health Obesity Education Initiative scientific evidence based categories14

Evidence categorySource of evidenceDefinition
ARandomised controlled trials (rich body of data)Provides a consistent pattern of findings with substantial studies
BRandomised controlled trials (limited body of data)Few randomised trials exist that are small in size and results inconsistent
CNon-randomised trials, observational studiesOutcomes are from uncontrolled non-randomised and/or observational studies
DPanel consensus judgmentPanel's expert opinion when the evidence is insufficient to place it in A to C