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A new study published in the Journal of the American Society of Nephrology has linked obesity to kidney problems after heart surgery.

According to the study, obesity increases the risk of acute kidney injury (AKI) following cardiac surgery and AKI represents a fivefold increase in mortality risk within 30 days after the procedure and is associated with longer hospital stays and a range of complications.

Researchers observed 455 people who underwent cardiac surgery in Boston and found that about 25 percent of them developed AKI after their procedure. Researchers also noted that patients with a higher body mass index (BMI) had a much greater risk. After adjusting for several other risk factors, the odds of AKI increased a staggering 26.5 percent for every five-point increase in a patient's BMI.

Researchers say an imbalance between the production of reactive oxygen and a biological system's ability to readily detoxify the reactive intermediates or easily repair the resulting damage could be the reason obesity influences AKI.

 The study's author, Frederic T. (Josh) Billings IV, said this discovery is very beneficial.

"By identification of this mechanism, we now may be able to target intraoperative oxidative stress with the hope of reducing kidney injury following cardiac surgery," Billings said. "That may be particularly appropriate for obese individuals."

The authors noted that the finding is "consistent with the hypothesis that oxidative stress partially mediates the association between BMI and AKI."

"I think we learned something really important by doing the mediation analysis," said biostatistician Jonathan Schildcrout, one of the study's authors. "You could have just examined the BMI and AKI association, and everybody would have said, 'OK, obese people have higher risk of AKI.' "When you learn the mechanism, you can start to learn how to intervene to prevent the injury."