WEDNESDAY, Sept. 20, 2017 (HealthDay News) -- For many obese Americans, weight-loss surgery can be a path to losing lots of unhealthy pounds.

But new research suggests it can also lead to a long-term loss of healthy red blood cells, otherwise known as anemia.

In a study of U.S. veterans who got a common form of weight-loss (bariatric) surgery, "anemia rates are high 10 years after," conclude a team led by Dr. Dan Eisenberg, a bariatric surgeon at Stanford School of Medicine.

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One specialist who reviewed the findings wasn't surprised.

"Anemia is a common problem in patients who have undergone gastric bypass, and this study sheds light on the severity of the problem in patients who don't receive adequate treatment," said Dr. Allison Barrett. She directs bariatric surgery at Long Island Jewish Forest Hill, in Forest Hill, N.Y.

She believes the research "proves that complications of surgery, such as vitamin and mineral deficiency, can also be lessened through improved follow-up."

In the new study, Eisenberg's team tracked outcomes for 74 older male veterans, average age 51, who underwent a common type of weight-loss surgery called Roux-en-Y gastric bypass.

The overall rate of anemia before surgery was 20 percent, the team noted, but by 10 years after surgery that number had risen to 47 percent.

Follow-up care was crucial, however. According to the study, anemia was much more common among patients who did not have close follow-up with a weight-loss surgeon. For these patients, anemia rates rose from 22 percent before surgery to 57 percent a decade later.

In comparison, for patients who did consult regularly with their weight-loss physician, anemia rates barely budged -- from 13 percent before surgery to 19 percent a decade later.

According to bariatric surgeon Dr. Mitchell Roslin, that's because simple treatments can curb the deficiencies that might occur after surgery.

"In gastric bypass, the first portion of the intestine is bypassed and iron is absorbed preferentially in that area," explained Roslin, who directs obesity surgery at Lenox Hill Hospital in New York City.

"In general, this can be compensated for with appropriate supplements," he said, "but patients that do not take prescribed supplements are likely to develop deficiencies."

According to Roslin, the take-home lesson from the study is that "bariatric surgery does help [curb obesity], but patients should not believe they are cured and must be compliant and continue to follow medical direction for the duration of their life."

The study was published Sept. 20 in the journal JAMA Surgery.

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more on weight-loss surgery.