Bariatric Surgery Could Mitigate Risk for Diabetes Complications


A prospective study of more than 120 patients who underwent bariatric surgery sheds additional light on the potential benefits incurred by undergoing weight loss surgery in people with obesity.

Brian C. Callaghan, MD, MS | Credit: Michigan Medicine

Brian C. Callaghan, MD, MS
Credit: Michigan Medicine

A new study from clinicians in the University of Michigan (U-M) Health Department of Neurology suggests undergoing weight loss surgery could attenuate some of the negative risks associated with diabetes among people with obesity.

An analysis of 120 patients who underwent bariatric surgery for obesity, results of the study suggest undergoing bariatric surgery was associated with improvements in peripheral neuropathy as well as all metabolic risk factors associated examined in the study, including fasting glucose and retinopathy, with the exception of blood pressure and total cholesterol levels.1

“Our findings suggest that bariatric surgery likely enables the regeneration of the peripheral nerves and, therefore, may be an effective treatment for millions of individuals with obesity who are at risk of developing diabetes and peripheral neuropathy,” said senior investigator Brian C. Callaghan, MD, MS, a neurologist at U-M Health and the Eva L. Feldman, MD, PhD, Professor of Neurology at U-M Medical School.2

With the rising obesity epidemic placing undue strain on health systems, bariatric surgery has grown in popularity an efficacious option for combatting obesity, with recent endorsement in American Academy of Pediatrics obesity guidelines underlining the growing role of bariatric surgery in obesity management.3 In the current study, Callaghan and team of investigators sought to build on the existing knowledge base surrounding the effects of bariatric surgery on diabetes complications in those with a BMI exceeding 35 kg/m2.1

With this in mind, investigators designed a prospective cohort study of participants with obesity who had undergone bariatric surgery at the University of Michigan bariatric surgery clinic. Of note, all participants were required to be at least 18 years of age, have a BMI exceeding 35 kg/m2 but below 70 kg/m2, and not be using anticoagulants.1

Per study protocol, participants underwent metabolic phenotyping and diabetes complication assessments at baseline and 2 years after bariatric surgery. With enrollment occurring from April 2015-May 2018, investigators enrolled an overall study cohort of 127 patients. The overall study cohort had a mean age at baseline of 44.9 (SD, 12.8) years, 79.5% were female, and 78.7% were White.1

Of the 127 patients enrolled in the trial, 26 withdrew or were lost to follow-up. Of the 101 patients who completed follow-up, 79 completed in-person follow-up. This subgroup had a mean age at baseline of 46.0 (SD, 11.3) years, 73.4% were female, and 79.7% were White.1

Investigators had multiple primary outcomes of interest for the study. The primary outcome of interest for peripheral was a change in intra-epidermal nerve fiber density (IENFD) at the distal leg and proximal thigh, the primary outcome of interest for cardiovascular autonomic neuropathy was a change in the expiration/inspiration (E/I) ratio, and the primary outcome for retinopathy was a change in the mean deviation on frequency doubling technology testing.1

Upon analysis, results of the study indicated participants experienced a mean reduction in body mass of 31 (SD, 18.4) kg at 2 years. Results suggested IENFD of the proximal thigh improved during follow-up (3.4±7.8 fibers/mm; P <.01) while IENFD of the distal leg was stable (0.1±4.1 fibers/mm; P=.92). Further analysis indicated theprimary CAN measure (E/I ratio) was stable (E/I ratio, -0.01±0.1; P=.89) during follow-up, the primary retinopathy outcome was stable (Mean deviation, -0.2±3.0; P=.52) during follow-up, and multiple patient-oriented outcomes improved significantly during follow-up.1

“Given the natural history of peripheral neuropathy decline in patients with obesity, even stability in nerve fiber density may be considered a successful result,” said lead investigator Evan Reynolds, PhD, lead statistician for the NeuroNetwork for Emerging Therapies at Michigan Medicine.2 “Therefore, our findings of stability of nerve fiber density in the leg and improvement in nerve fiber density at the thigh indicate that bariatric surgery may be a successful therapy to improve or reverse peripheral neuropathy for patients with long-term metabolic impairment.”


  1. Reynolds, E.L., Watanabe, M., Banerjee, M. et al. The effect of surgical weight loss on diabetes complications in individuals with class II/III obesity. Diabetologia (2023).
  2. Fromson N. Bariatric surgery may reverse diabetes complications for people with obesity. Michigan Medicine Health Lab. Published April 7, 2023. Accessed April 10, 2023.
  3. Hampl SE, Hassink SG, Skinner AC, et al. Clinical Practice Guideline for the Evaluation and Treatment of Children and Adolescents With Obesity. Pediatrics. 2023;151(2):e2022060640. doi:10.1542/peds.2022-060640
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