Obesity is one of the greatest pandemics of the 21st century with 30 million new cases each year. In France each year, 60,000 bariatric surgery procedures are performed.

Many preoperative diets have been proposed in the literature with some studies giving positive results. But these diets are often strict and can have adverse effects on metabolism. Very few studies have described the PSMF diet. The hypothesis would be that this diet is associated with a reduction in liver volume with a reduction in steatosis.

Inclusion criteria:

• Adult patient (≥18 years old)
• Man and woman
• Patient operated on at the HUS between 2010 and 2021 for bariatric surgery
• Patient not objecting to the reuse of their data for scientific research purposes.

Exclusion criteria:

- Patient who has expressed his opposition to the reuse of his data for scientific research purposes.

Adult patients (≥18 years old) operated on at the HUS between 2010 and 2021 for bariatric surgery