A new meta-analysis (combining the results of multiple studies) has reported that women with breast cancer who are obese have poorer survival than women with breast cancer who are not obese, confirming the results of previous studies. The authors conducted a systematic search of the MEDLINE, EMBASE and CINAHL databases to identify original studies concerning the effects of obesity on survival in women newly diagnosed with breast cancer. A total of 43 studies that enrolled women diagnosed with breast cancer between 1963 and 2005 were included in the meta-analysis.

Women who were obese at diagnosis were 33% more likely not to survive breast cancer. The survival difference varied only slightly depending on whether body mass index or waist-hip ratio was used as the measure of obesity. However, the authors comment that no study has elucidated the causal mechanism and there is currently no evidence that weight loss after diagnosis improves survival. Consequently, the authors conclude that there is currently no reason to place the additional burden of weight loss on women already burdened with a diagnosis of cancer.