Some breast cancer patients tend to put on a few pounds after undergoing chemotherapy due to the presence of gut bacteria, bringing upon certain metabolic changes after treatment, according to Bar-Ilan University researchers.Director of Oncology at the Galilee Medical Center at Bar-Ilan Dr. Ayelet Shai initiated the research after noticing the symptoms occurring in many of her patients. Chemotherapy is already known to increase the risk of developing high blood pressure as well as glucose intolerance, the latter being a condition for diabetes.”In my clinical work with women recovering from breast and gynecological tumors, I have seen many of them gain weight following treatment and experience difficulty returning to their original weight. When I read in medical literature about the link between the microbiome and obesity in people without cancer, I thought it would be interesting to see if the microbiome of patients is one of the causes of obesity and other metabolic changes,” said Shai.The study itself, enlisted a sample of 33 women who were about to begin their chemotherapy treatments for breast and gynecological cancers. They were weighed once before treatment, and once five weeks into treatment.Stool samples were used to genetically characterize the microbiome of each of the women.Nine gained weight to a degree designated as significant, being 3% or more. The women in the study had a less diverse set of gut bacteria and bacterial strains compared to that of women who did not experience weight gain, which showed that the composition of intestinal bacteria could predict which women will gain weight as a result of chemotherappy.To further prove their assumptions, the researchers transferred the gut microbiota of women who gained weight into mice, who subsequently developed glucose intolerance and signs of a chronic inflammatory condition detected within the blood – concluding that bacteria is partially responsible for the metabolic changed that lead to weight gain when undergoing chemotherapy.We have shown for the first time that the pre-treatment microbiome of patients that gained weight following chemotherapy is different than the microbiome of patients that did not gain weight, and that fecal transplantation from patients that gained weight results in glucose intolerance, adverse lipid changes and inflammatory changes in germ-free mice,” says Prof. Omry Koren, an expert in gastrointestinal bacteria at the Azrieli Faculty of Medicine of Bar-Ilan University.Shai and Koren are currently running a follow up study surverying a largeing sample than the first, examining the gut microbiome of women at the end of chemotherapy treatment to back their assumptions and further understand the effect of chemotherapy on bacterial composition – as well as the effect of chemotherapy on obesity in mice after gut micriobiome transplantation.”We hope that in the future we will be able to identify those women who are at risk for weight gain through a simple examination and perhaps even suggest ways to prevent this phenomenon,” Shai concluded.The researchers findings were published in the scientific journal BMC Medicine.