Endocrine Abstracts

Introduction: Vitamin B1 (VB1) deficiency can occur in patients with obesity and after bariatric surgery (BS). Nevertheless, pre-operative measurements of VB1 are still controversial. The relationship between serum VB1 and weight loss after BS has not been reported previously.

Objectives: To study the association between pre-operative VB1 levels and weight loss after BS.

Methods: Retrospective study of patients submitted to bariatric surgery - laparoscopic Roux-en-y gastric bypass (RyGB) or vertical gastrectomy (VG) with 1 year follow-up and a pre-operative serum VB1 measurement. The primary endpoint was reaching a body mass index (BMI) ≤ 25 Kg/m². Patients with VB1 < 147 nmol/l and with VB1 ≥ 147 nmol/l (mean VB1 value) were compared. Multivariable logistic regression analysis models were built with variables associated with weight loss (age, sex, and type of surgery) along with additional variables added to the model one-at-a-time. The latter were those variables with different distribution between groups and with possible interference with VB1 levels and function.

Results: We analysed 98 patients. Mean VB1 levels were 147 (33) nmol/l. No patients were supplemented for VB1. Patients with VB1 levels ≥ 147 nmol/l had higher haemoglobin (P=0.02), leukocyte counts (P=0.005) and TSH (P=0.05). There were no differences observed between groups regarding age, sex, type of surgery, diabetes status, initial BMI, gamma-glutamyl transpeptidase (GGT), insulin, calcium, magnesium, zinc, folic acid, vitamin B12, albumin, or vitamin D levels. Patients with VB1 levels ≥ 147 nmol/l reached a BMI ≤25 Kg/m² more often 58.3% vs 36.0%, P=0.03, and had lower BMI at 1-year [24.2 (23.0-27.2) vs 25.8 (23.6-27.9) Kg/m², P=0.06] and higher excess BMI loss [100.9% (18.5) vs 94.5% (14.8), P=0.06] although not statistically significant. In the multivariate logistic regression analysis, for each 10 nmol/l increase in VB1 the OR (95% CI) for the association with the primary endpoint was 1.25 (1.07-1.46), P=0.004 adjusted for age, sex, and surgery type. This association was similar after additional one-at-a-time adjustments for: haemoglobin, leukocytes, calcium, magnesium, GGT, insulin, diabetes status, TSH, folic acid, vitamin B12, zinc and hepatic steatosis.

Conclusions: VB1 is associated with weight loss after BS. Per each 10 nmol/l increased the risk of reaching normal BMI 1-year after BS increased by 25%.