Lung cancer surgery patients are most likely to have complications and to die if they’re either too thin or fat, a new study suggests.

The study included more than 41,000 people who had lung cancer surgery between 2009 and 2014. Patients were categorized according to their body mass index (BMI) — an estimate of body fat based on weight and height.

While the study couldn’t prove cause-and-effect, people who were either underweight or severely obese had the highest rates of complications and death following surgery, according to the study. The findings were to be presented Tuesday at the annual meeting of the Society of Thoracic Surgeons in Phoenix.

Weight “is associated with a patient’s overall physiology and health, but overweight people need to have more muscle to carry the extra weight around,” study co-leader Dr. Trevor Williams of the University of Chicago, explained in a society news release.

As for underweight people, Williams believes they are more likely to be frail, “which is associated with impaired strength, reduced activity and being easily fatigued. There also may be an association with immune system impairment. All of these factors adversely affect outcomes after lung surgery.”

There was one silver lining, however: The study found that overweight and slightly obese patients had a lower risk of complications than normal weight patients.

This means that “patients who are overweight or [slightly] obese should not be fearful of lung [surgery] because they have the best outcomes after surgery,” study co-lead author Dr. Mark Ferguson, also of the University of Chicago, said in the news release.

“However, though not specifically included in our study, any increase in exercise capacity prior to surgery can only be beneficial — so keep walking!”, he said.

Two experts agreed that weight can have an impact on surgical outcomes.

“Both very thin and [very] obese patients have higher rates of complications following removal of part of the lung,” said Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City. The obese [in the study] “had the highest risk for complications,” he noted, “likely a result of associated conditions like diabetes, hypertension [high blood pressure] and heart disease.”

Dr. Colin Brathwaite is chairman of the department of surgery at Winthrop-University Hospital in Mineola, N.Y. He said doctors have long known that weight influences surgical outcomes, and he believes the new data “is important in defining preoperative risk” for patients.

Experts note that findings presented at medical meetings are considered preliminary until published in a peer-reviewed journal.

More information

The U.S. National Cancer Institute has more about lung cancer.

Source: HealthDay