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Effectiveness and Safety of a Very Low-Calorie Ketogenic Diet on Weight Regain Following Bariatric Surgery

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Obesity is one of the major public health problems worldwide and bariatric surgery is considered the gold standard treatment for severe obesity. Although the literature supports the safety and efficacy of the very low-calorie ketogenic diet (VLCKD) in patients with obesity, there is no study analyzing the use in case of failure or weight regain after bariatric surgery. This work has the purpose of assessing the response to a VLCKD (Pnk® method) in this population.


We have conducted an observational, retrospective, and descriptive study with the analysis of medical charts of private offices where patients were examined between 2014 and 2019, totalizing 11 participants who underwent Roux-en-Y gastric bypass (RYGB) without a reduction of 50% in body weight excess or any weight regain after the surgery. The patients followed the first stage of a commercial weight loss program (Pnk® method) which consists of a VLCKD (600–800 kcal/day), low in carbohydrates and lipids.


A significant reduction was observed (p-value < 0.05) in weight, body mass index (BMI), abdominal circumference (AC), and glycated hemoglobin (A1C) post-ketogenic diet. Uric acid, transaminases, urea, and creatinine values did not show differences between pre- and post-ketosis. During the course of the study, no serious adverse events were reported.


This study has shown that the ketogenic diet can be recommended as an effective and safe treatment for patients who progressed with insufficient weight loss or regain after bariatric surgery.

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We thank all of the investigators and patients who took part in this study.

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Correspondence to Livia Lugarinho Correa.

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Ethical Approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

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Informed consent does not apply (Annex A).

Conflict of Interest

The authors Livia Lugarinho Correa, Adriana Moretti, Priscila Alves Medeiros de Sousa, Leticia Dinis, Mariana Fuganti de Souza, Isabel Tostes, Maitane Nuñez-Garcia and Ignacio Sajoux declare that they have no conflict of interest. The Pronokal personnel (Maitane Nuñez-Garcia and Ignacio Sajoux) was involved in the study design and revised the final version of the manuscript, without intervention in the analysis of data, statistical evaluation, and final interpretation of results of this study.

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Key Points

• VLCKD produces significant improvement in weight, BMI, and AC after RYGB.

• VLCKD produces a significant reduction in A1C levels without changes in kidney and liver functions.

• VLCKD is effective and safe in case of insufficient weight loss or regain after bariatric surgery.


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Correa, L.L., Moretti, A., de Sousa, P.A.M. et al. Effectiveness and Safety of a Very Low-Calorie Ketogenic Diet on Weight Regain Following Bariatric Surgery. OBES SURG 31, 5383–5390 (2021).

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