Weight loss surgery could lead to a condition which can result in memory loss, according to US research.
Frequent vomiting after surgery can lead to the syndrome
The syndrome - Wernicke encephalopathy - affects the nervous system and brain, and can lead to confusion and the inability to co-ordinate movement.
The study, published in Neurology, the journal of the American Academy of Neurology, says the syndrome is caused by a lack of vitamin B1, or thiamine.
Frequent vomiting after surgery can lead to the syndrome, the study found.
The researchers identified 32 cases of Wernicke encephalopathy after obesity surgery, 27 involving women.
The report says it is not clear if the condition is more common in women, or if there were more cases in women because 75% of obesity surgery patients are female.
Dr Colin Waine, of the National Obesity Forum, urged against avoidance of weight loss surgery, for those most in need.
"Clearly we need to note this report and we must be aware of it but I don't think it should lead to a knee-jerk rejection," he said.
"The results of weight loss surgery can be very good.
"Some people are so at risk that they are going to die from other causes without surgery.
"The risk of encephalopathy is probably much less than the risk they are facing from obesity."
'Outlook usually good'
The syndrome was found to occur within one to three months of weight loss surgery, such as gastric bypass surgery, although one case occurred 18 months after surgery.
Study author Sonal Singh, of Wake Forest University School of Medicine in North Carolina, urged those who had undergone weight loss surgery to take their prescribed vitamin supplements and be alert for symptoms such as vomiting, confusion, visual changes and lack of co-ordination.
"When people who have had weight loss surgery start experiencing any of these symptoms, they need to see a doctor right away," he said.
"If treated promptly, the outlook is usually good."
For treatment, patients are given vitamin B1 through an IV or injection.
Of the 32 people in the study, 13 made a full recovery, though others continued to have problems such as memory loss.
Singh said more studies are needed to determine how often the syndrome occurs after weight loss surgery.