Anaemia and weight outcomes 5 years after metabolic and bariatric surgery - a prospective cohort study

Metabolic and bariatric surgery (MBS) is an effective long-term treatment for obesity but is also associated with nutritional deficiencies and risk of recurrent weight gain (RWG). Anaemia is a common complication, particularly after Roux-en-Y gastric bypass (RYGB). Long-term comparative data on anaemia and clinical outcomes after MBS are limited. This study aimed to evaluate anaemia, nutritional deficiencies, weight trajectories, and late clinical deterioration (defined as either RWG >30 % from the initial weight loss or exacerbation of an obesity-related comorbidity) five years after RYGB, sleeve gastrectomy (SG), or medical treatment (MT).

This prospective, non-randomized cohort study included 971 adults with obesity (BMI ≥35 kg/m²) from the BASUN study. Participants underwent RYGB (n = 388), SG (n = 201), or MT (n = 382). Hematologic parameters, supplement use, weight outcomes, and obesity-related complications (using medication data as surrogate markers) were assessed at baseline and five years. Follow-up data were available for 538 participants. Anaemia prevalence increased significantly in the RYGB group (3.0 %-12.2 %, p < 0.05), especially among women. No significant differences in anaemia or iron deficiency were found between supplement users and non-users in either surgery group. Late clinical deterioration occurred in 23.5 % of the MT group, 10.0 % of the RYGB group, and 13.5 % of the SG group.

Anaemia and iron deficiency increased five years post-RYGB, regardless of supplement use, suggesting current iron supplementation regimens may be inadequate. Alternative strategies are needed. A substantial proportion of patients experienced late clinical deterioration, highlighting the importance of long-term follow-up after obesity treatment.

March 03, 2015; NCT03152617.