Abstract: ObjectiveTo assess the association between adult weight gain（AWG）and postmenopausal breast cancer risk. MethodsPubMed， EMbase， Web of science， CBM， CNKI， VIP and Wanfang databases were searched. Two reviewers extracted data independently according to methods of  Cochrane Collaboration. Statistical analysis was performed using Stata 11.0 software. ResultsA total of 15 prospective observational trials with 445 453 participants （17 285 cases） were included in the metaanalysis. The metaanalysis showed that  the highest AWG group had an increase in the risk of postmenopausal breast cancer  when compared with control group（RR=1.42，95%CI=1.331.51，P<0.05）. Significant nonlinear doseresponse  association was identified between AWG and breast cancer risk in postmenopausal wom (P<0.05). Individuals with AWG >12 kg yielded the increased postmenopausal breast cancer risk（P<0.05）.ConclusionThis metaanalysis highlighted that AWG contributed to increased breast cancer risk in a nonlinear doseresponse manner in postmenopausal women. The association between AWG and postmenopausal breast cancer risk is statistically significant for more than 12 kg in AWG.

Key words: breast neoplasms, body mass index, overweight, metaanalysis