The research question was supported by clear inclusion criteria. Only trials published in English were sought, so neither publication bias nor language bias could be ruled out, but tests for publication bias suggested it was not present. Trial selection, data extraction and trial quality assessment were performed by two people, which reduced the risk of reviewer error and bias.
Trial quality was assessed and taken into consideration and some aspects of heterogeneity were investigated. The authors stated that these findings might only be generalisable to women. The synthesis using meta-analysis appears to have been appropriate.
The lack of high-quality primary trials means that the reliability of the authors' conclusions is unclear. The conclusion that combined smoking cessation and behavioural weight-control interventions did not produce any harm might have been an overstatement as the authors only investigated two specific harms: diminished abstinence and increased weight gain.