A Cochrane review [Abstract] 1 included 18 studies. For weight, in the RCTs and CBAs (controlled before and after studies) from lower income countries, experimental group children gained an average of 0.39 kg (95% CI 0.11 to 0.67) over an average of 19 months and 0.71 kg (95% CI 0.48 to 0.95) over 11.3 months respectively. Results for weight were mixed in higher income countries. For height, results were mixed; height gain was greater for younger children. Attendance in lower income countries was higher in experimental groups than in controls; our results show an average increase of 4 to 6 days a year. Math gains were consistently higher for experimental groups in lower income countries; in CBAs, the standardized mean difference was 0.66 (95% CI 0.13 to 1.18). In short-term studies, small improvements in some cognitive tasks were found.
Comment: The quality of evidence is downgraded by inconsistency (heterogeneity in interventions and outcomes). and by indirectness (differences in reported outcomes).
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