Review: nutrition after weight-loss surgery

Overview

Lupoli R et al.. World J Diabetes 2017 · PMID 29204255 · DOI 10.4239/wjd.v8.i11.464

Deficiencies are common but can be prevented with lifelong supplements and monitoring.

Does the study support the specific claim? Partly · Methodological quality: low

Original publication

Plain-language summary

Scientific in-depth review

1. Full reference

Authors

Lupoli R, Lembo E, Saldalamacchia G, Avola CK, Angrisani L, Capaldo B

Journal

World J Diabetes

Year

2017

Identifier

PMID 29204255 DOI 10.4239/wjd.v8.i11.464 · PMC5700383

Verification

verified – PubMed E-utilities efetch, 2026-10-25

Retracted

no

Corrections

none

Extent checked

full text

Conflicts of interest and funding

Authors declare no conflicts of interest; no funding stated (invited manuscript).

2. Research question

Long-term nutritional issues after bariatric surgery

3. Study design and population

Study design

Narrative review – Narrative review (invited manuscript), no systematic search or appraisal methods reported

Population

Bariatric patients

Country

Italy (authors, Federico II University, Naples); literature international

Period

Published November 2017

Sample size

n/a

4. Methods and endpoints

Exposure / intervention

Bariatric procedures (AGB, SG, RYGB, BPD/DS)

Endpoints

Micronutrient and macronutrient deficiencies (anaemia, iron, B12, folate, vitamin D, calcium, fat-soluble vitamins, thiamine, minerals), bone loss/fractures, protein malnutrition, weight regain, pre-operative deficiencies

Statistical methods

Narrative; prevalence ranges from cited studies

5. Actual results

Results

Cited prevalences: anaemia 33-49% within 2 years (about 17% after sleeve, 45-50% after RYGB/BPD); 10-12% anaemic before surgery. Low ferritin in >30% at 5 years (similar after RYGB and SG). B12 deficiency 19-35% at 5 years after BPD/RYGB; purely restrictive procedures usually not associated. Folate deficiency 9-39%. Bone loss 8-13% after surgery vs 1-2% after non-surgical weight loss; one population study: 15-year fracture incidence 58% vs 24% (RR 2.3). Calcium deficiency almost 10%; hypovitaminosis D 25-73% after surgery vs 25-80% before. Thiamine deficiency up to 49%. Protein malnutrition 7-21% after BPD, 13% at 2 years after long-limb RYGB. Pre-operative: vitamin D insufficiency about 90%, deficiency about 60%; B12 deficiency about 18%; iron deficiency 20-47%; zinc 10.2%. Weight regain after SG 5.7% at 2 y to 75.6% at 6 y; RYGB failure 7-50%. Mean surgical mortality 0.3%. Overall: 42% reduction in cardiovascular risk and 30% reduction in all-cause mortality.

Absolute risks

Only prevalence ranges from cited studies (see results); no pooled estimates.

Authors' conclusion

Nutritional deficiencies are a relevant long-term problem; guidelines recommend lifelong monitoring, pre-surgery assessment and correction, and multivitamin plus calcium/vitamin D supplementation for all patients; procedure-specific monitoring schedule provided.

6. Strengths

• Covers the range of deficiencies by procedure type
• Highlights pre-existing deficiencies and guideline-based monitoring

7. Weaknesses

• Non-systematic narrative review; selection of cited studies not described
• Wide prevalence ranges from heterogeneous studies and definitions
• No quality appraisal of primary studies
• Many estimates come from malabsorptive procedures (BPD) that are now rarely used (<2%)

8. Risk of bias

Orienting tool

none (narrative review; no standard tool fits)

Type of assessment

structured assessment based on the full text by a single reviewer (no formal double review)

Full formal assessment

no

Overall risk of bias

not assessable

Rationale

Narrative review; no standard risk-of-bias tool applies. Structured single-reviewer judgement from full text; a formal assessment would require two independent reviewers and a protocol.

Full-text review (25 October 2026): Added procedure-specific prevalence ranges (anaemia, iron, B12, folate, vitamin D, protein), pre-operative deficiency rates, fracture and bone-loss figures, weight regain ranges, monitoring schedule; structured narrative-review judgement (not assessable).

9. Assessment of the statistical interpretation

Prevalence ranges are not comparable across studies and are partly pre-existing (vitamin D, iron). Deficiency risk depends strongly on procedure: highest after BPD/RYGB, lower after sleeve (e.g. anaemia about 17%; B12 deficiency usually not associated with restrictive procedures).

10. Relevance to the specific claim

Supports C-BAR-05.

11. Independent contrary findings

12. Transferability to Germany and Europe

Applicable; European authors and guideline-based recommendations.

13. Overall methodological judgement

Supports that deficiencies are common after bariatric surgery and that lifelong monitoring/supplementation is guideline practice, with important context: many deficits exist before surgery, are procedure-dependent and preventable. It does not support the claim that the sleeve abolishes stomach function; it states the opposite.

14. Open questions

15. Linked fact checks

• Bariatric surgery causes lifelong deficiencies of iron, B12, vitamin D, calcium and protein, requiring lifelong supplements. – Studies supporting the claim
• Sleeve gastrectomy is a physiologically wrong operation and a 'transgression against God's creation', because the stomach is not a bag but an endocrine, muscular and immune organ whose functions are lost. – Studies contradicting or limiting the claim

Use by the Tayebat archive

Note: according to the archive, the studies were compiled by the archive operators. Whether Dr. Elawady himself cited this study is not established.

What the archive says about the study

Listed in the archive bibliography only; the archive gives no specific interpretation.

A. What was actually studied?

Nutrition after surgery

B. What did the authors find?

Deficiencies common, partly pre-existing, preventable

C. What conclusions do the authors themselves draw?

Lifelong monitoring/supplements

D. What does the archive derive from it?

Supports 'lifelong dependence on supplements'.

E. Is this derivation scientifically justified?

Supports the need for supplements; the review also states high pre-operative deficiency rates, procedure-dependence (lower after sleeve), preventability, and a 30% reduction in all-cause mortality, which the archive does not mention.

Adequacy of the interpretation (by the archive)

not applicable