Patients who have undergone bariatric surgery may experience malnutrition in the months after their weight loss surgery. To better help these patients devise sustainable and healthier weight loss goals, clinicians should learn how the signs of malnutrition present after bariatric procedures to help patients avoid deficiencies, experts recommended during ASPEN 2024 Malnutrition Awareness Week.

Speaker Neil Floch, MD, the director of bariatric surgery at Greenwich Hospital and an associate professor of surgery at the Yale School of Medicine, in New Haven, Conn., explained that there is always some risk for deficiency related to bariatric surgeries. To better support patients who may experience nutrient deficiencies, clinicians should work toward understanding the rates of different vitamin and mineral deficiencies associated with all the common bariatric procedures.

He emphasized that it is especially important to understand how malnutrition manifests in populations after bariatric surgery because the need for these procedures is likely to increase in the United States and the world. “We have an obesity epidemic and it is growing,” Dr. Floch said.

Dr. Floch explained that despite the malnutrition risks, surgery for long-term weight loss is still worth suggesting to patients who struggle with obesity. “[Weight loss] is difficult without help,” said Dr. Floch, noting that medications are helpful but not as effective as some surgeries. “What the surgery does is it’s really the un-diet. It decreases our appetite, decreases our hunger [and] increases our satiety.”

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Deficiencies Per Bariatric Procedure

Dr. Floch’s presentation at ASPEN focused on malnutrition associated with the most common forms of weight loss surgery in the United States: gastric sleeve (59%), gastric bypass (18%), and biliopancreatic diversion with duodenal switch (1%) (Surg Obes Relat Dis 2022;18[9]:1134-1140). Patients who have opted for a sleeve gastrectomy are very likely to struggle with vitamin B12 (9%), folate (15%) and iron (43%) deficiencies, he said, whereas patients who have received a gastric bypass are often deficient in B12 (30%-50%), vitamin D (30%-50%) and iron (25%-50%) (Curr Obes Rep 2017;6[3]:286-296). Those who opted for a biliopancreatic diversion often are deficient in vitamin A (60%-70%), vitamin D (40%-100%) and vitamin K (60%-70%).

Despite the concerns about malnutrition in post-bariatric patients, other health issues do decline after patients undergo weight loss surgery. The risk for five-year mortality declines by 89% after surgery (N Engl J Med 2007;357[8]:753-761). Dr. Floch said this is because the risk for death from diabetes-related complications is reduced by 92%, and the risk for death from heart disease goes down by about 52%.

Causes of Malnutrition

But what is the mechanism behind those micronutrient deficiencies? Speaker Angela Wolfenberger, MS, RDN, LD/N, a bariatric dietitian at the Queens Comprehensive Weight Management Program, in Kamuela, Hawaii, said that in the weeks after a bariatric procedure, patients eat a diet extremely low in calories. Some patients will eat from 800 to 1,000 calories a day in the months after surgery, she said, which leaves little room for consuming enough micronutrients. Some patients also struggle with consuming enough protein after a procedure if their taste in dairy and meat shifts. “This contributes to the necessity of lifelong micronutrient supplements,” Ms. Wolfenberger said.

One of the contributing factors associated with malnutrition comes is a lack of follow-up care and instruction from medical providers. In one study, only about 54% of post-bariatric patients reported a follow-up visit with their medical team, and that dropped to 10% at around three years after a weight loss procedure (Obes Surg 2004;14[8]:1070-1079).

Other factors complicate post-op care and nutrition support, such as more bariatric patients turning to medical tourism for weight loss procedures (Obes Surg 2023;33[4]:1060-1072). “There’s few guidelines for follow-up care for these patients,” Ms. Wolfenberger said, noting that there are many information gaps regarding patients who go abroad. “More research is needed to determine if patients are receiving their required follow-up after having surgery in another country.”

Ms. Wolfenberger also noted that teams and surgeons should ask about a history of previous procedures and regarding medication that a patient regularly takes. Some medicines make it harder for the body to absorb nutrients, and providers should take note of what a patient is taking, particularly anti-gout medications, anticoagulants and laxatives.

Ms. Wolfenberger also said many patients who struggle with malnutrition before surgery are likely to do so afterward due to their diets. Assessing nutrient intake before a bariatric procedure is key to supporting a patient afterward.

Signs of Malnutrition

Most bariatric patients struggle with a vitamin D deficiency before and after their surgery. The signs of this deficiency include fatigue, alopecia and muscle weakness, among others (Endocr Pract 2019;25[12]:1346-1359). Vitamin D deficiency often comes along with calcium deficiency, Ms. Wolfenberger said. The best way to alleviate this is supplementing with calcium citrate and vitamin D2 during mealtimes, she said.

Other vitamin and mineral malnutrition issues have not been readily documented in post– bariatric procedure patients. “They can be common, they can be uncommon, they can be rare, but they’re really not documented,” Ms. Wolfenberger said, emphasizing that better follow-up would help practitioners fill in these information gaps.

Some patients do not show obvious signs of being nutrient deficient early on. Eventually, symptoms such as severe hair loss, brittle hair, muscle pain and restless leg syndrome begin to manifest. Severe skin issues such as dermatitis occur when a patient has severe protein and B vitamin deficiencies. These deficiencies also can be detected from brittle and dry nails. The mouth also can show signs of nutrient deficiencies. For example, patients who are not consuming enough B vitamins will have sores on their gums. That same deficiency also causes a burning tongue.

“The causes of malnutrition are multifactorial after bariatric surgery [and are] primarily due to medication noncompliance, other medications and malabsorption syndromes,” Ms. Wolfenberger said. “They should be observed by all practitioners, not just the bariatric team, because of the loss to follow-up over the years.”

The GI Perspective

So what’s a gastroenterologist to do? Knowing the guidelines can help.

“I generally use the [American Society for Metabolic and Bariatric Surgery] guidelines for screening for micronutrient deficiencies after bariatric surgery [Obes Surg 2023;33(8):2557-2572],” Octavia Pickett-Blakely, MD, MHS, an associate professor of clinical medicine and the director of the GI Nutrition, Celiac Disease and Obesity Program at the University of Pennsylvania, in Philadelphia, told Gastroenterology & Endoscopy News.

“We always assess [labs] when we see patients [and] repeat nutrition labs,” noted Reem Z. Sharaiha, MD, MSc, an associate professor of medicine and the director of bariatric and metabolic endoscopy at Weill Cornell Medicine, in New York City. Dr. Sharaiha told Gastroenterology & Endoscopy News that it’s also important for patients to see a nutritionist.

—Angely Mercado and Meaghan Lee Callaghan

The panel was supported by Nestlé Health Science.

This article is from the January 2025 print issue.