Effect of Metabolic and Bariatric Surgery Associated with Changes in Weight Loss, Free Leptin Index, and Soluble Leptin Receptor

<b>Objective:</b> To compare the clinical and metabolic impact of the relationship between leptin, serum soluble leptin receptor (sOB-R), free leptin index (FLI), and ghrelin among different metabolic and bariatric surgeries (MBSs) in patients with severe obesity. <b>Method:</b> Cohort study including 194 patients >18 years old diagnosed with obesity (body mass index (BMI) ≥ 30 kg/m²) undergoing bariatric surgery at the General Hospital of Mexico. Participants were distributed into three surgical groups: Roux-en-Y gastric bypass (RYGB) (n = 36), one anastomosis gastric bypass (OAGB) (n = 86), and sleeve gastrectomy (SG) (n = 72); all operations were performed laparoscopically. Pre- and post-surgical measurements were taken, including anthropometric measurements, lipid profile, glycated hemoglobin (HbA1c), leptin, sOB-R, ghrelin, and FLI. Protocol registration: DI/16/304/04/090. <b>Results:</b> A total of 194 patients with obesity were analyzed, the average weight was 114.9 ± 24 kg, and the preoperative BMI was 43.1 ± 8.0 kg/m². Three types of MBSs were compared. Post-surgery, all groups showed a significant percentage of excess weight loss (%EWL), for example, in OAGB 65.6 ± 12.2%EWL at 12 months (<i>p</i> < 0.0001). In addition, ghrelin levels decreased significantly, especially in a short time compared with pre-surgery levels (from 4 ± 2.5 to 1.6 ± 1 ng/mL per first week (<i>p</i> < 0.0001)). Similarly, leptin diminished in a short time (<i>p</i> < 0.01). Soluble leptin receptor showed differences in the biochemical behavior of leptin, with FLI decreasing significantly (<i>p</i> < 0.003) after one year (<i>p</i> = 0.001). <b>Conclusions:</b> All techniques were effective in reducing body weight, %EWL, and hormonal modulation during the first three months. In addition, ghrelin and FLI levels partially increased as a physiological adaptation to weight loss and resumption of food intake, without reaching initial values.