Effect of bariatric surgery on the prevalence of micronutrient deficiencies and protein status

Abstract

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.

INTRODUCCIÓN: La cirugía bariátrica (CB) es el método más eficaz para el tratamiento de la obesidad grave a largo plazo. Sin embargo, la CB se asocia a déficits de micronutrientes. OBJETIVO: aumentar el conocimiento del riesgo de deficiencias nutricionales y del estado proteico en sujetos candidatos a CB. MÉTODOS: Se evaluó prospectivamente el estado nutricional de los pacientes antes y después de la CB (bypass gástrico (BPG) y gastrectomía tubular (GT)]. Se evaluó, mediante dos estudios prospectivos la eficacia y la seguridad de normalizar los niveles de 25-hydroxy VD (25 (OH) D) mediante dos algoritmos de suplementación distintos. Obtuvimos información sobre la alta prevalencia de deficiencia de hierro al caracterizar el estado de hierro con la evaluación de índices de inflamación sistémica. Finalmente, se realizaron dos estudios observacionales prospectivos para evaluar los efectos de la ingesta proteica (IP) sobre la masa libre de grasa (MLG) y los cambios en el estatus proteico después de la pérdida de peso inducida por BS. Finalmente, se diseñó un estudio aleatorizado y controlado para determinar el efecto de dos niveles de IP (estándar versus alto) después de CB sobre el balance de nitrógeno, la composición corporal, el gasto energético, saciedad y los niveles plasmáticos de aminoácidos de cadena ramificada, así como el efecto de la suplementación proteica a largo plazo. RESULTADOS: Los déficits nutricionales son frecuentes en nuestra población candidata a CB. La GT y BPG conllevan un riesgo nutricional comparable. Una dosis fija (2.000 UI) de suplementos de VD es tan eficaz y segura como una dosis diaria individualizada para normalizar niveles. Al considerar hs-CRP como marcador inflamatorio, el déficit de hierro podría ser identificado en dos tercios de los candidatos a CB. Los suplementos proteicos son útiles para alcanzar el objetivo proteico tras CB. IP de> 60 g / día o 1,1 g / kg de peso ideal / día se asocia con una mejor retención de MLG. Los resultados del estudio piloto apoyan la viabilidad del protocolo propuesto. CONCLUSIÓN: Nuestros datos subrayan la necesidad de la evaluación de parámetros nutricionales antes y después de la CB. Consideramos que los resultados de este proyecto contribuyen significativamente a mejorar el conocimiento en el área de nutrición y composición corporal después de la CB.