key visual comparison deficiencies

Comparison of deficiencies up to 3 years after a Gastric Sleeve or a Gastric Bypass

Deficiencies in micronutrients after bariatric operations are frequent. Theoretically, prevalence depends on the kind of surgery and which parts of the gastro-intestinal system are bypassed. In a non-randomized prospective trial, deficiencies after a Gastric Sleeve (50 patients) were measured and compared to Roux-en-Y Gastric Bypass (86 patients), for up to 3 years after surgery. Postoperatively, all patients were prescribed daily multivitamin supplements.

Hemoglobin and ferritin deficiencies after Gastric Sleeve and Gastric Bypass

Two years after surgery, the percentage of excess weight loss was statistically comparable between the two techniques, ranging from 81% (Gastric Sleeve) to 88% (Gastric Bypass). Preoperatively, deficiencies were found for hemoglobin, iron, ferritin, zinc and vitamin B12. Over time, levels of hemoglobin and ferritin further decreased in both groups, resulting in a higher deficiency prevalence. No statistically significant difference was found in deficiencies for Gastric Sleeve or Gastric Bypass patients.

Overall deficiency prevalence before and after surgery

Prior to surgery, more than half of the patients had at least one deficiency of vitamin D (23%), zinc (14%), albumin (6%), vitamin B12 (3%), folate (3%) or iron (3%). These deficiency levels increased after surgery for all nutrients except albumin.

Fewer vitamin B12 and vitamin D deficiencies after SG

In the first two postoperative years, the Gastric Sleeve procedure led to significantly fewer vitamin B12 and vitamin D deficiencies compared to the Gastric Bypass. However, in both groups, nutrient deficiencies often occurred. For a full overview of deficiency prevalence, see figure 1.


Nutrient Preoperatively Postoperatively (overall) Postoperatively (Sleeve) Postoperatively (Bypass)
Vitamin B12 3% 76% 18% 58%
Vitamin D 23% 84% 32% 52%
Secondary hyperparathyroidism 8% 47% 14% 33%
Folate 3% 34% 22% 12%
Iron 3% 46% 18% 28%
Zinc 14% 71% 34% 37%

Most deficiencies occurred during the first postoperative year, and most of them could be treated successfully by adding the lacking nutrient to the patient’s supplementation regime. This indicates that regular assessments of a patient’s nutritional status are required to identify and treat deficiencies at an early stage.

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Gehrer, S., Kern, B., Peters, T. et al. Fewer Nutrient Deficiencies After Laparoscopic Sleeve Gastrectomy (LSG) than After Laparoscopic Roux-Y-Gastric Bypass (LRYGB)—a Prospective Study. OBES SURG 20, 447–453 (2010).

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