Background <p>Stapler line reinforcement during sleeve gastrectomy (LSG) was assessed thoroughly in the context of postoperative complications focusing on leakage and bleeding. However, the effect of stapler line reinforcement techniques on the short- and long-term weight loss is still unclear and lacking. We hypothesize that inverting of the stapler line by Lembert suturing could lead to further additional reduction of the remnant gastric volume and accordingly a more significant weight reduction.</p> Methods <p>Retrospective analysis of patients that underwent LSG (2012–2018) from the two university hospitals. The first hospital routinely performed oversewing with inversion of the stapler line (first group, Lembert suture), while the second university hospital performed LSG without stapler line oversewing and inversion, but routinely used VeraSeal glue (second group, non-Lembert); both groups were compared in terms of weight loss and complications.</p> Results <p>Four hundred eighty and 550 patients underwent LSG in the first and second hospital, consequently. The mean BMI change and EBWL at 1, 3, and 5 years were better in the first group than in second group. The mean last follow-up BMI was significantly lower in Lembert group (29.8 ± 5.2kg/m²) than in non-Lembert group (32.9 ± 6.7 kg/m²), <i>P</i> = 0.001. The mean EBWL at last follow-up point was significantly better for the Lembert group as compared to non-Lembert group (73.7 ± 26.59 versus 57.12 ± 27.71, <i>P</i> = 0.001).</p> Conclusions <p>Lembert suture line oversewing and inversion in LSG is associated with noticeable improvement in weight loss outcomes at 1, 3, and 5 years and last follow-up compared to LSG with VeraSeal gluing.</p>