Body composition changes after bariatric surgery in adults with obesity and hepatic steatosis

doi:10.4240/wjgs.v18.i7.118280

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Publication Name

World Journal of Gastrointestinal Surgery

ISSN

1948-9366

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Baishideng Publishing Group Inc, 7041 Koll Center Parkway, Suite 160, Pleasanton, CA 94566, USA

Retrospective Cohort Study

Copyright: ©Author(s) 2026. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution-NonCommercial (CC BY-NC 4.0) license. No commercial re-use. See permissions. Published by Baishideng Publishing Group Inc.

World J Gastrointest Surg. Jul 27, 2026; 18(7): 118280
Published online Jul 27, 2026. doi: 10.4240/wjgs.v18.i7.118280

Body composition changes after bariatric surgery in adults with obesity and hepatic steatosis

Lilian Kethelyn Teixeira Schmitt, Luis F Ferreira, Claudio Cora Mottin, Bruna Goularth Lacerda, Paula Rosales Zubiaurre, Joise Munari Teixeira, Claudio A Marroni, Sabrina Alves Fernandes

Lilian Kethelyn Teixeira Schmitt, Bruna Goularth Lacerda, Joise Munari Teixeira, Postgraduate Program in Hepatology, Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre 90050-170, Rio Grande do Sul, Brazil

Luis F Ferreira, Department of Hepatology, Federal University of Health Sciences of Porto Alegre, Porto Alegre 90050-170, Rio Grande do Sul, Brazil

Claudio Cora Mottin, Paula Rosales Zubiaurre, Obesity and Metabolic Syndrome Center, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre 90160-090, Rio Grande do Sul, Brazil

Claudio A Marroni, Department of Hepatology, Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre 90050-170, Rio Grande do Sul, Brazil

Sabrina Alves Fernandes, Santa Casa de Porto Alegre Hospital Complex, Porto Alegre 90020-090, Rio Grande do Sul, Brazil

Author contributions: Schmitt LKT contributed to the conceptualization, data curation, funding acquisition, investigations, methodology, project administration, resources, visualization, and original draft preparation; Ferreira LF contributed to the data curation, formal analysis, funding acquisition, investigations, methodology, project administration, resources, software, supervision, validation, writing, review, and editing; Mottin CC, Lacerda BG, Zubiaurre PR, and Teixeira JM contributed to the conceptualization, data curation, funding acquisition, investigations, methodology, project administration, resources, visualization, and original draft preparation; Marroni CA and Fernandes SA contributed to the conceptualization, methodology, project administration, supervision, validation, visualization, writing, review, and editing.

Institutional review board statement: The study was approved by the Research Ethics Committee of the Pontifical Catholic University of Rio Grande do Sul (CEP-PUCRS), under approval number 1729522, and received the Certificate of Ethical Appreciation (CAAE) number 58388816.3.0000.5336. The research complies with the ethical guidelines established by Resolution No. 196/96 of the Brazilian National Health Council and follows the principles of the Declaration of Helsinki for research involving human subjects. Data management was conducted in accordance with the Brazilian General Data Protection Law (LGPD - Law No. 13,709/2018).

Informed consent statement: Participation in the study required volunteers to read and sign the informed consent form.

Conflict-of-interest statement: The authors have no conflicts of interest to declare.

STROBE statement: The authors have read the STROBE Statement—checklist of items, and the manuscript was prepared and revised according to the STROBE Statement—checklist of items.

Data sharing statement: Access to the final database was restricted exclusively to members of the research team.

Corresponding author: Sabrina Alves Fernandes, PhD, Researcher, Santa Casa de Porto Alegre Hospital Complex, Professor Annes Dias, 295, Porto Alegre 90020-090, Rio Grande do Sul, Brazil. sabrinaafernandes@gmail.com

Received: December 29, 2025
Revised: January 24, 2026
Accepted: March 18, 2026
Published online: July 27, 2026
Processing time: 211 Days and 9.9 Hours

Abstract

BACKGROUND

Obesity drives multiple chronic conditions, including metabolic steatotic liver disease. Bariatric surgery is effective in inducing weight loss and improving metabolic dysfunction, potentially modifying liver-related outcomes. However, short-term effects on body composition and noninvasive liver markers remain incompletely characterized. We hypothesized that bariatric surgery significantly improves body composition and metabolic parameters associated with hepatic steatosis.

AIM

To investigate body composition and liver-related biochemical changes after bariatric surgery in patients with obesity and hepatic steatosis.

METHODS

This retrospective cohort study evaluated 91 adults undergoing Roux-en-Y gastric bypass at a tertiary hospital. Data collected preoperatively and 6 months postoperatively included body composition by bioelectrical impedance analysis, laboratory tests, and noninvasive fibrosis scores. Paired Student’s t-test or Wilcoxon test was applied, with significance set at 5%.

RESULTS

Body mass index decreased significantly (e.g., 42.1 ± 5.8 kg/m² vs 32.6 ± 4.9 kg/m²; P < 0.001). Visceral fat and body fat percentage were markedly reduced (P < 0.001). Alanine aminotransferase, glucose, triglycerides, and creatinine levels declined significantly. Serum vitamin D and vitamin B12 increased (P < 0.01). Muscle and cellular mass decreased (P < 0.05). Platelet count changed modestly, while fibrosis scores remained stable.

CONCLUSION

Bariatric surgery improves body composition and metabolic markers associated with hepatic steatosis, while early fibrosis indices remain unchanged. Loss of muscle mass underscores the need for nutritional strategies and long-term follow-up.

Keywords: Obesity; Steatotic liver disease; Bariatric surgery; Body composition; Hepatic steatosis

Core Tip: Six months after bariatric surgery, a significant reduction in body mass index, visceral fat, and metabolic parameters was observed, associated with an improvement in liver enzymes, especially alanine aminotransferase, suggesting regression of hepatic steatosis. Bioelectrical impedance analysis demonstrated a decrease in body fat, with relative preservation of muscle mass, although there is a risk of lean mass loss. Non-invasive indices of hepatic fibrosis, such as aspartate aminotransferase to platelet ratio index and fibrosis-4 index, did not show early changes, reinforcing the need for prolonged follow-up and individualized nutritional monitoring.