Results of the quality analysis of the included studies
| Quality criteria | Fairburn et al 17 | Jones et al 18 | Ronchi et al 19 | Schendel et al 21 | Bianchi et al 20 | Hsieh et al 22 | Veys et al 23 | de Ruiter et al 24 |
| Sample randomisation | No | No | No | No | No | No | No | No |
| Comparison between treatments | No | No | No | Yes | No | No | No | No |
| Blind assessment | No | No | No | No | No | Yes | Yes | No |
| Description of measurements | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Statistical analysis | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Defined inclusion/exclusion criteria | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Report of follow-up | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes |
| Risk of bias | High | High | High | Unclear | High | Unclear | Unclear | High |
*Risk of bias assessment: high=0–4, ‘yes’; unclear=5–6, ‘yes’; low=7, ‘yes’.