**Acknowledgements**

The authors are grateful to the Bariatric Surgery Unit of the Hospital Ramón y Cajal, and to the patients. we would like to thank all the people who have contributed to this work, especially Marta Cobo and Yolanda Gutiérrez.

This work was supported by the Spanish Ministry of Science and Innovation, Instituto de Salud Carlos III (ICI21/00012), and co-funded by the NextGenerationEU and PRTR. MPA was supported by a Rio Hortega contract (CM19/00069) and JA by a Sara Borrell contract (CD21/00059), both from the Instituto de Salud Carlos III and co-funded by the European Social Fund (ESF, "Investing in your future").
