High Incidence of Iron Deficiency Following Bariatric Surgery

By Matthew Constantin, PhD

Approximately one-third of the US population is classified as obese and nearly 5% are morbidly obese [1]. Obesity has proven to be a health problem that is not easily treated by diet, exercise and medical treatment. Over the last few decades, weight loss surgery has emerged as an effective treatment for obesity.

Gastric bypass, laparoscopic adjustable gastric banding, vertical banding gastroplasty, biliopancreatic diversion, and biliopancreatic diversion with duodenal switch are some of the surgical procedures that are commonly performed to help induce weight loss in those affected with obesity. While the overall mortality rate from these procedures is typically less than 1% [2], bariatric surgery is associated with other short- and long-term side effects.

Short-term complications can range from blood clots in the lungs to surgical incision infections. Long-term complications include metabolic abnormalities as well as vitamin and mineral deficiencies such as iron, vitamin B12, vitamin D, folate, and calcium. Iron deficiency and anemia can have a strong negative impact on overall quality of life and may prove difficult to treat. A recent review article in The American Journal of Hematology by Aileen L. Love of the Weill Cornell Medical Center in New York, NY provides an overview of the association between iron deficiency and bariatric surgery.

Why Do WLS Patients Present Iron Deficiency?

Many studies report that iron deficiency occurs anywhere from 6 to 50% of those who undergo weight loss surgery within months to years following the surgery [3]. There are several reasons why this type of deficiency happens in gastric bypass patients.

Meat Intolerance

There is a trend for people to avoid red meat after surgery, which is one of the major sources of iron. In fact, one study reported that 27 out of 69 gastric bypass patients experienced vomiting following the intake of meat [4]. Furthermore, one researcher found that up to 50% of his bypass patients experience chronic meat intolerance following surgery [5]. However, decreased dietary intake of iron is not the sole explanation for iron deficiency. While gastric bypass patients tend to have greater meat tolerance than patients who undergo gastric banding, one controlled clinical trial actually demonstrated that only the bypass patients experienced iron deficiency, despite having the higher tolerance [6].

Lower Gastric Acid Secretion

Surgeries that separate the antrum from the gastric pouch, such as gastric bypass, result in removal of the parietal cells, which produce gastric acid. Gastric acid is necessary for the iron metabolism. Reduction of gastric secretion impairs iron absorption. Research has shown that rates of iron deficiency are lower in people who undergo banding procedures, which do not affect gastric secretions [7].

Duodenum Exclusion

The exclusion of the duodenum, the section of the small intestine that absorbs iron, from the digestive continuity is another reason why iron deficiency occurs. In gastric bypass patients, the duodendum is bypassed, resulting in lower serum iron and hemoglobin concentrations compared to those who undergo banding procedures [8]. For this reason, the biliopancreatic diversion with duodenal switch procedure that preserves some function of the duodenum may offer protection from iron deficiency.

Blood Loss

Blood loss is another factor that may lead to iron deficiency. Gastrointestinal blood loss in bypass patients is a possibility due to the exclusion of bowel loops form the digestive tract.

Iron Deficiency and Anemia Can Occur in Special Patient Populations

Certain groups of people who undergo bariatric surgery also are at an increased risk of developing iron deficiencies. These include women, especially those who become pregnant following surgery, and children.

Women who menstruate are at high risk for developing iron deficiency and anemia following surgery due to lower stores of iron in their body prior to undergoing surgery and loss of iron during menstruation. No matter what bariatric procedure women receive, they typically have lower hemoglobin and serum iron levels after surgery than men.

While bariatric surgery helps to improve a woman’s fertility, becoming pregnant may actually aggravate the rate of iron deficiency since the body’s requirement for iron increases during pregnancy. This anemia not only poses a risk for the mother, but also the unborn baby. Research suggests that iron deficient mothers are more likely to have pre-term or low-birth weight infants [9]. Because of this banding procedures may be a better option for women who plan to have children following weight loss surgery.

The other special population at risk for iron deficiency following surgery are obese children and adolescents. While many surgeons are performing bariatric procedures on adolescents with low mortality rate, one major drawback is that surgery can result in long-term nutritional deficiencies including iron deficiency. Like their older counterparts, girls are typically more affected by this than boys.

Treatment for Iron Deficiency

Since it is well known that iron deficiency occurs following weight loss surgery, most surgeons prescribe a multivitamin to their patients. However, these vitamins may not contain enough iron to prevent the iron deficiency or anemia from happening. For this reason, the addition of vitamin C to an oral iron supplementation may help prevent and treat the condition. Research has shown that vitamin C increases the acidity found in the gastrointestinal tract that may help iron be more readily absorbed. In others, parenteral iron treatment and blood transfusions or even surgical interventions may be required to help increase iron absorption.

Since iron deficiency can become a major issue in patients following weight loss surgery, it is important for patients to work with their physician to set-up a lifelong follow-up strategy that includes ongoing monitoring of hematological and iron levels.


  1. Ogden CL, Carroll MD, Curtin LR, et al. Prevalence of overweight and obesity in the United States, 1999–2004. JAMA 2006;295:1549–1555.
  2. Maggard MA, Shugarman LR, Suttorp M, et al. Meta-analysis: Surgical treatment of obesity. Ann Intern Med 2005;142:547–559.
  3. Simon SR, Zemel R, Betancourt S, et al. Hematologic complications of gastric bypass for morbid obesity. South Med J 1989;82:1108–1110.
  4. Halverson JD, Zuckerman GR, Koehler RE, et al. Gastric bypass for morbid obesity. A medical-surgical assessment. Ann Surg 1981;194:152–160.
  5. Avinoah E, Ovate A, Charuzi I. Nutritional status seven years after Roux-en-Y gastric bypass surgery. Surgery 1992;111:137–142.
  6. Brolin RL, Robertson LB, Kenler HA, et al. Weight loss and dietary intake after vertical banded gastroplasty and Roux-en-Y gastric bypass. Ann Surg 1994;220:782–790.
  7. Cooper Pl, Brearley LK, Jamieson AC, et al. Nutritional consequences of modified vertical gastroplasty in obese subjects. Int J Obes 1999;23:382–388.
  8. Sugarman HJ, Londry GL, Kellum JM, et al. Weight Loss with vertical banded gastroplasty and Roux-Y gastric bypass for morbid obesity with selective versus random assignment. Am J Surg 1989;157:93–102.
  9. Ramussen K. Is there a causal relationship between iron deficiency or iron deficiency anemia and weight at birth, length of gestation and prenatal mortality? J Nutr 2001;131:590s–601s.

About the Author

Matthew Constantin, Ph.D. has a special interest in the field of obesity treatment in large part due to numerous cardiovascular studies he currently is involved in as research scientist at Washington University in St. Louis, Missouri. On his web site, Matthew offers Medifast promotional coupons and a savings coupon for BistroMD, two medically approved diets available in the US.

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