A significant number of patients who have stomach surgery to lose weight develop peripheral nerve damage, research has found.
Stomach stapling is major surgery
A team at the Mayo Clinic in Minnesota found patients complained of pain, tingling or numbness.
They believe the damage is caused by malnutrition as the body is less able to absorb nutrients following surgery.
The research, focused on stomach stapling and gastric bypass surgery, will be published in Neurology.
The researchers say the problem can probably be prevented by proper nutritional care.
Neurologist Dr Jim Dyck, who worked on the study, said: "Surgeons who do weight-reduction surgery and the general public and should be aware that nerve damage is a frequent consequence of the surgery.
"I'm not saying that people shouldn't have this surgery, but I am saying that there are real potential complications and that good follow-up care is necessary."
The researchers found 16% of weight-reduction surgery patients they studied developed a peripheral neuropathy.
These ranged from minor tingling or numbness in the feet to severe pain and weakness confining patients to wheelchairs.
However, patients who were part of nutritional programmes before and after their weight loss surgery generally did not develop problems.
Conversely, those who did not attend nutritional clinics were among the most at risk, along with those who suffered prolonged periods of nausea and vomiting, and those who lost weight quickly.
Some forms of malnutrition, such as thiamine deficiency, are well known to cause peripheral neuropathy.
Weight reduction operations
Gastric bypass: Staples are used to close off a large section of the stomach, leaving just a small pouch to digest food.
Vertical banded gastroplasty: Uses a band and staples to create a small stomach pouch.
Dr Dyck said: "This is a life-changing operation. It's like having transplant surgery - you need long-term follow-up."
The research focused on 435 patients who had undergone either Roux-en-Y gastric bypass or vertical banded gastroplasty.
Reports of nerve damage were much more common than in people who had undergone other forms of abdominal surgery, such as gallbladder removal.
The researchers say they do not known if it is possible to reverse the effects through improved nutrition.
Dr Ian Campbell, chairman of the National Obesity Forum said it was known that people who underwent stomach stapling surgery had a reduced ability to absorb nutrients from their food - but this often improved with time.
He said other forms of surgical treatment, such as silastic banding, which involves putting a band around the top of the stomach, were available. But stomach stapling was certainly an option for people with extreme obesity.
He said: "Gastric bypass is only ever considered for people whose lives are at threat because of their obesity.
"It is major surgery, but the risks are sometimes justified, as it can be a life-saving procedure.
"Better to have a tingling in your feet than to have rip-roaring type 2 diabetes."