Bariatric surgery helps patients lose weight and improves insulin sensitivity, but follow-up and postoperative management are critical for enduring success and overall health, according to the five experts who presented the virtual Scientific Sessions symposium Bariatric Surgery—What Is New, and What Lessons Have We Learned?
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The symposium’s first presenter, Michael Roden, MD, Director of the German Diabetes Center and Professor and Chair of Endocrinology and Metabolic Diseases at Heinrich-Heine University in Düsseldorf, Germany, described how bariatric surgery affects changes in body mass index (BMI), metabolism, and insulin sensitivity. He reviewed a study from the German Diabetes Center that used comprehensive phenotyping to assess the effects of gastric bypass surgery and sleeve gastrectomy in the first year after intervention. Phenotyping included muscle mitochondrial mass, muscle-targeted lipidomics, and muscle genome-wide methylomics. The researchers concluded that bariatric surgery not only reduces BMI, but also causes changes in adipose tissue, which leads to transient and long-term changes in muscle function and insulin sensitivity, which contributes to a new metabolic homeostasis.
“Bariatric surgery, as we can expect immediately after the intervention, causes massive release of free fatty acids from the adipose tissue. These free fatty acids enter tissues, such as the skeletal muscle, where they give rise to diacylglycerols and activate protein kinase C, which prevent the very early improvement in insulin resistance,” Dr. Roden said. “On the other hand, they are excessively burned in mitochondria. But due to lipotoxicity and maybe also oxidative stress or impaired antioxidant capacity, there’s also a transient reduction in mitochondrial mass. These metabolic changes most likely lead to changes in DNA methylation, which on the long-term are contributing to beneficial muscle reprogramming, which correlates with improved insulin sensitivity.”
Most patients reach their lowest weight following gastric bypass surgery about a year after the procedure, said Maria L. Collazo-Clavell, MD, Professor of Medicine in the Department Internal Medicine and the Division of Endocrinology, Diabetes, Metabolism, and Nutrition at the Mayo Clinic. If patients don’t meet their weight loss expectations in the first year, it’s important to identify what’s causing any unwanted weight gain and intervene to manage potential complications, she said. Factors that contribute to weight gain include decreased restriction of calorie intake, recurrence of hunger and cravings, inactivity, illness, and medications.
Megan M. Kelsey, MD, MS, Associate Professor of Pediatrics, Pediatric Endocrinology, Medical Director of Adolescent Bariatric Surgery, and Director of Lifestyle Medicine Endocrinology at Children’s Hospital Colorado, discussed indications for pediatric bariatric surgery.
Most of the literature about pediatric bariatric surgery comes from the Teen-Longitudinal Assessment of Bariatric Surgery (LABS) and the Adolescent Morbid Obesity Surgery Study (AMOS). The American Academy of Pediatrics currently supports referral of youth with severe obesity for bariatric surgery evaluation because the benefits outweigh the risks as long as there are no contraindications, Dr. Kelsey said. Recent guideline updates include adding pediatric definitions for severe obesity above the 95th percentile, loosened comorbidity criteria for consideration in class II severe obesity, and elimination of the need for specific qualifying medical criteria if class III severe obesity is present.
“And really, most importantly, there’s no longer recommendation to wait until linear growth is complete,” she said.
While diabetes remission after gastric bypass surgery is well documented, a small group of patients develop hypoglycemia after surgery, said Marzieh Salehi, MD, MS, from the Diabetes Division at the University of Texas at San Antonio and the Bartter Research Unit at Audie Murphy Hospital. Diagnosis of hypoglycemia after gastric bypass is complex and requires a detailed review of the patient’s medical history and confirmation of Whipple’s triad—presence of symptoms when glucose is low (plasma glucose <55 mg/dl) and relief of symptoms when glucose is normalized.
“Hypoglycemia after gastric bypass is exclusively postprandial and associated with larger circulatory insulin and glucagon-like peptide 1 (GLP-1) concentrations,” Dr. Salehi. “To date, dietary modification and medical and surgical interventions that reduce the post-meal glycemic spikes and insulin secretion are most effective therapeutic strategies.”
Anne Schafer, MD, Associate Professor of Medicine and of Epidemiology & Biostatistics at the University of California, San Francisco, and Chief of Endocrinology and Metabolism at the San Francisco VA Health Care System, said bariatric surgery can also affect bone density and strength. Since bariatric surgery patients often experience dramatic weight loss, it can make their skeleton more fragile and put them at risk for fractures. Dr. Schafer recommended checking 25-hydroxyvitamin D levels in all patients undergoing bariatric surgery.
“Postoperatively, patients should take a high-potency bariatric multivitamin, even gastric band patients,” she said. “Calcium and vitamin D supplements are recommended universally. Labs every six months for two years and then annually thereafter.”
Lab tests should include calcium, albumin, 25-hydroxyvitamin D, and parathyroid hormone. Protein intake is important following bariatric surgery, as is exercise and resistance training, Dr. Schafer added.
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