Nutritional Deficiencies in Patients with Severe Obesity before Bariatric Surgery: What Should Be the Focus During the Preoperative Assessment?

Background: Nutritional deficiencies are a well-recognized long-term complication following bariatric surgery. The presence of preoperative deficiencies has been shown to be predictive of postoperative deficiencies. Objective: The aim of the study was to investigate the prevalence of micronutrient deficiency in a large sample of patients with severe obesity preoperatively, and to determine whether such deficiencies may be related to patient's sex, body mass index, or ethnic subgroup. Design: A cross-sectional study of data collected at the time of the preoperative evaluation. Participants/setting: Data were collected during the preoperative evaluation of 872 bariatric surgery candidates in a university hospital in Israel between 2011 and 2018. The patients were 72.9% women, with a mean age of 37.9±12.1 years and mean body mass index of 42.4±4.7 Main outcome measures: Nutritional deficiencies according to blood assays. Data on anthropometrics, comorbidities, and demographic characteristics was also collected. Statistical analyses: Baseline differences between patient subgroups were analyzed using independent-samples t test, analysis of variance, or χ² test. Results: Deficiencies of vitamin D, iron, folate, vitamin B-12, elevated parathyroid hormone and low transferrin saturation were present in 75.2%, 42.6%, 28.5%, 8.5%, 35.5%, and 70% of patients, respectively. Nutritional deficiencies were significantly more common among women compared with men for iron (45.9% vs 33.5%; P=0.002), low transferrin saturation (77.7% vs 44.6%; P<0.001), vitamin D (77.5% vs 69.2%; P=0.019) and elevated parathyroid hormone level (39.5% vs 22.9%; P=0.002). Iron, transferrin saturation, and vitamin D deficiencies were more prevalent in Arab patients compared with Jewish patients: 59.6% vs 36%; P<0.001, 80.2% vs 62.8%; P=0.003, and 85.1% vs 71.6%; P<0.001, respectively. Vitamin D and iron deficiency were more common among higher body mass index subgroups (P=0.004 and P=0.040, respectively). Conclusions: The results indicate a high prevalence of nutritional deficiencies, mainly of iron and vitamin D in bariatric surgery candidates. Patients at higher risk for nutritional deficiencies include those with higher body mass index, women, and Arabs.