Resumen de Effect of bariatric surgery on the prevalence of micronutrient deficiencies and protein status
Background: Bariatric surgery (BS) is the most effective long-term therapy for the treatment of severe obesity. Benefits of BS include a reduction of overall and cardiovascular mortality, incidence of first occurrence of fatal- or nonfatal-cardiovascular events, prevention and remission of type 2 diabetes mellitus, and improved quality of life. Nonetheless, BS is associated with potential complications amongst which micronutrient deficiencies are relevant. Aim: Against this background, the overall aim of this PhD project was to better understand the increased risk for nutritional deficiencies and protein status in subjects undergoing BS. Methods: We prospectively evaluated the nutritional status of obese individuals prior to BS, and following the drastic reduction of daily energy intake, anatomical changes, and massive weight loss associated with the two currently most commonly performed surgical techniques [gastric bypass (GBP) and sleeve gastrectomy (SG)]. Additionally, to gain insight specifically on how to address the high prevalence of vitamin D (VD) deficiency, we performed two open-label, prospective studies aiming at evaluating the efficacy and safety of achieving 25-hydroxy VD (25(OH)D) levels ≥75 nmol/L with two different supplementation algorithms. Similarly, we gained insight on the reported high prevalence of iron deficiency by characterizing iron status with the evaluation of indices of systemic inflammation. Finally, we performed two observational prospective studies to evaluate the effects of dietary protein intake (PI) on fat free mass (FFM, as assessed from bioelectrical impedance or DEXA) and protein status changes after BS-induced weight loss. As further step in this research path, a randomized control trial proposal has been designed to determine the effect of two levels of PI (standard versus high) after BS on the nitrogen balance, body composition, energy expenditure, perceived satiety, and plasma levels of branched chain amino acids (BCAA) and insulin sensitivity, as well as the feasibility of protein supplementation up to one year after BS. This translational research protocol integrates mechanistic, metabolic, and energy homeostasis outcomes. Preliminary results of a pilot study of that trial are presented as part of this thesis project to demonstrate feasibility of the protocol. Results: Nutritional deficiencies are commonly found in a Mediterranean severely obese population undergoing BS, with those deficiencies being more prevalent than in normal weight individuals. Of note, SG- and GBP-patients experience similar long-term changes in dietary intake. Indeed, when micronutrient intake from supplements was not taken into account, mean daily dietary intake of all evaluated micronutrients was below current dietary reference intakes (DRIs). Interestingly, SG and GBP carry comparable post-surgical nutritional risk. Low VD and elevated PTH levels were the most prevalent nutritional abnormalities after BS. In clinical practice, a single fixed high dose (2,000 IU) of VD supplementation is as effective and safe as an individualized daily dose of cholecalciferol to achieve 25(OH)D levels ≥75 nmol/L after BS. When considering hs-CRP as inflammatory marker, impaired iron status could be identified in two thirds of BS candidates. Protein supplements are helpful in achieving the PI goal after BS, with PI thresholds of >60 g/d or 1.1 g/kg Ideal Body Weight/day being associated with better FFM retention. The results of our pilot study support feasibility for a larger Randomized Control Trial with to address the association between PI and NB, BCAA, body compositions changes, REE, glucose homeostasis, and satiety after BS. Conclusion: Our data underscores the need for the evaluation of nutritional parameters prior to- and following-BS. We deem results of this PhD project significantly contribute to improve knowledge in the area of nutrition and body composition after BS.
