National Institutes of Health Obesity Education Initiative scientific evidence based categories14
| Evidence category | Source of evidence | Definition |
|---|---|---|
| A | Randomised controlled trials (rich body of data) | Provides a consistent pattern of findings with substantial studies |
| B | Randomised controlled trials (limited body of data) | Few randomised trials exist that are small in size and results inconsistent |
| C | Non-randomised trials, observational studies | Outcomes are from uncontrolled non-randomised and/or observational studies |
| D | Panel consensus judgment | Panel's expert opinion when the evidence is insufficient to place it in A to C |