The study is believed to be the first study to compare the nutritional status of severely obese teens who did not undergo weight loss surgery to those who did have surgery - finding that at leastyears after undergoing gastric bypass surgery, teens and young adults maintained significant weight loss but were at risk of nutritional deficiencies, particularly low iron, mild anemia and low vitamin D.
The team, led by Dr Stavra Xanthakos, director the Surgical Weight Loss Program for Teens at Cincinnati Children's, also found low iron and low vitamin D in severely obese teens who did not undergo weight loss surgery. Those who didn't have surgery also had low levels of protein in their blood.
"We knew there were nutritional difficulties in teens who had undergone bariatric surgery, but everyone thought it was primarily the surgery that caused these problems since gastric bypass excludes the portion of the small intestine where many nutrients, especially iron, are most absorbed," said Xanthakos.
"What this shows us is that nutritional deficiencies occur even in teens who don't undergo surgery. Severely obese patients should be screened for nutritional deficiencies, regardless of whether they've undergone weight loss surgery."
The researchers studied 79 obese teens who either received weight loss surgery or were evaluated but did not receive surgery. These participants were evaluated between 2001 and 2007 and contacted to participate in the study between 2011 and 2014.
Eight years on average after surgery, the team found that the patients had experienced "durable and significant" weight loss, about 28%, while those who didn't receive surgery had not lost weight.
However, both groups were at risk from nutritional deficiencies, said the team - who presented their data at the annual meeting of the Pediatric Academic Societies in Vancouver, Canada.
Indeed, obese teens were found to be at risk from low iron and vitamin D irrespective of whether they received the surgery.