Background: Currently, bariatric surgery is the most effective treatment for severe obesity and its metabolic complications; however, 15-35% of the patients that undergo bariatric surgery do not reach their goal for weight loss. The aim of this study was to determine the proportion of patients that didn't reach the goal of an excess weight loss of 50% or more during the first 12 months and determine the factors associated to this failure. Methods: We obtained the demographic, anthropometric and biochemical information from 130 patients with severe obesity who underwent bariatric surgery in our institution between 2012 and 2017. We used self-reports of physical activity, caloric intake and diet composition. An unsuccessful weight loss was considered when the patient lost < 50% or more of the excess weight 12 months after surgery. We compared the characteristics between the successful and unsuccessful groups in order to find the factors associated with success. Results: We included 130 patients (mean age 48 ± 9 years, 81.5% were women). One year after surgery, 26 (20%) had loss < 50% EBW. Unsuccessful surgery was associated with an older age, previous history of hypertension, abdominal surgery or depression/anxiety, also the number of comorbidities and unemployment affected the results. These patients loss enough weight to improve some of their comorbidities, but they are more prone to regain weight 2 years after surgery. Conclusions: A fifth of the patients undergoing bariatric surgery may not lose enough weight to be considered successful by current standards. Some patients may benefit from the surgery in the short term, but they are more likely to regain weight after 2 years. The factors influencing this result are still controversial but may be populationspecific. Early detection of the patients that are more likely to fail is imperative to establish additional therapeutic strategies, without denying them the opportunity of surgery or waiting for weight regain to occur.

Obesity, type 2 diabetes, arterial hypertension, decrease in immune response, cytokine storm, endothelial dysfunction, and arrhythmias, which are frequent in COVID-19 patients, are associated with hypomagnesemia. Given that cellular influx and efflux of magnesium and calcium involve the same transporters, we aimed to evaluate the association of serum magnesium-to-calcium ratio with mortality from severe COVID-19. The clinical and laboratory data of 1064 patients, aged 60.3 ± 15.7 years, and hospitalized by COVID-19 from March 2020 to July 2021 were analyzed. The data of 554 (52%) patients discharged per death were compared with the data of 510 (48%) patients discharged per recovery. The ROC curve showed that the best cut-off point of the magnesium-to-calcium ratio for identifying individuals at high risk of mortality from COVID-19 was 0.20. The sensitivity and specificity were 83% and 24%. The adjusted multivariate regression model showed that the odds ratio between the magnesium-to-calcium ratio ≤0.20 and discharge per death from COVID-19 was 6.93 (95%CI 1.6–29.1) in the whole population, 4.93 (95%CI 1.4–19.1, p = 0.003) in men, and 3.93 (95%CI 1.6–9.3) in women. In conclusion, our results show that a magnesium-to-calcium ratio ≤0.20 is strongly associated with mortality in patients with severe COVID-19.