Avaliação da composição corporal e do gasto energético em pacientes com anorexia nervosa acompanhadas em um serviço universitário de referência do estado de Minas Gerais

Abstract

Anorexia Nervosa (AN) is a complex eating disorder that combines mental and nutritional state abnormalities and results in severe weight loss and risk of malnutrition due to intense dietary restriction. The methods used to assess body composition in AN include anthropometry and electrical bioimpedance, and indirect calorimetry to estimate energy expenditure. During the weight restoration process, the body compartments in AN recover in different proportions and the isolated assessment of the body mass index is not able to assess the changes that occur in body composition. Objective: The aim of this thesis was to evaluate body composition and energy expenditure in AN patients in the active phase and in the recovery phase, comparing them to control group and seeking to verify, in greater depth, what happens to patients in recovery. Methods: This is an observational and cross-sectional study, with 34 female participants, 18 anorexics and 16 control subjects (CTR). Participants underwent anthropometric and electrical bioimpedance (BIA) assessments. Weight, height, body mass index (BMI), fat-free mass index (FFMI), fat mass index (FMI), appendicular muscle mass (AMM), fat-free mass (FFM), mass fat (MF), total body water (TBW), resistance (R), reactance (Xc) and phase angle (PA) were performed. To estimate resting metabolic rate (RMR) the predictive equations of Harris and Benedict (1918), Shebendach (1995), FAO/WHO (1985) and Buchholz (2003), and indirect calorimetry (CI) were used, as a reference method. Patients with AN were separated into two groups, according to the following criteria: patients with active- phase anorexia nervosa (APAN) - those with BMI < 18.5 kg/m2 and/or weight adequacy < 85% of ideal weight and presence of key symptoms (intense fear of gaining weight and body image disturbance); patients with anorexia nervosa in the recovered phase (ANrec) – those with previous AN, BMI value ≥ 18.5 kg/m2 and/or weight adequacy ≥ 85% of ideal weight maintained for a sustainable period, in partial or total remission of the key symptoms cited above. The key symptom was defined according to the Diagnostic and Statistical Manual of Mental Disorders, 5th edition, according to the assessment of the multidisciplinary team (psychologists and psychiatrists) of the institution. The differences of variables between the ANat x ANrec x CTR groups were analyzed with the Statistical Package for Social Science (SPSS) software version 25. For the analysis of body composition comparison, comparison of means and medians between groups was performed and ROC (receiver operating characteristic) curves were constructed. with the variables BMI, FFMI, FMI R, Xc, PA, FM, AMM, and ACT, with ANat x CTR and ANrec x CTR as comparison groups. Ordinal regressions were performed to establish correlations between the independent variables related to body composition and the allocation of patients in each of the 3 study groups (ANat, ANrec or CTR), according to previously defined criteria, as a dependent variable. Linear regression models were built to assess the correlation between independent variables of body composition and RMR, preceded by adjustment by FFM. To evaluate the use of predictive equations in estimating the RMR, using indirect calorimetry as a reference, means and medians of the 4 equations were compared, and the agreement between the predictive equations was evaluated using Bland-Altman graphs. and indirect calorimetry. Finally, we analyzed through Analysis of Variance (ANOVA) the distributions of percentage differences and their correlation with the means to verify the proportionality bias. At the end, single-sample t tests were applied for the percentage differences obtained, for each equation and for each clinical condition, to verify to what extent, mean differences were different from zero. Results: From the descriptive characteristics, there was no significant age difference between ANat, ANrec and controls (25.0 ± 8.6 years, 22.1 ± 6.9 years, 25.8 + 5.1 years P= 0.335), of the time of diagnosis between ANat and ANrec (85.0 ± 89.0 x 44.6 ± 48.5 months, P= 0.470). BMI, considered the main anthropometric measure of diagnosis and nutritional monitoring in AN, was different between ANat x ANrec and (15.9 ± 2.6 kg/m2 x 20.3 ± 2.2 kg/m2, P= 0.000 after Bonferroni correction), but there was no statistical difference between ANrec and controls (20.3 ± 2.2 kg/m2 x 22.28 ± 1.75 kg/m2). The FFM means (kg) (31.01 + 4.56 kg in ANt; 37.59 + 1.89 kg in ANrec and 44.56 + 4.64 kg CTR showed significant differences between the two phases of AN and controls. Among the main findings, after the ordinal regression analysis, the ability of the PA to distinguish ANrec and healthy controls stands out (estimate B = 0.123, P= 0.004 or 0.091, P= 0.008 in 2 different models). ACT and R resistance (kg) proved to be able to distinguish the study groups. FFMI did not remain in the final regression models. The phase angle (Beta = 141.28; CI: 99.99 - 182.56; P< 0.001) and the BMI (Beta = 48.55; CI = 32.60 - 64.51; P< 0.001) showed important correlation with the MRL corrected by FLM (R2= 0.699). TMR measurements were significantly lower in anorexics with low body mass and low FFM. In the evaluation of energy expenditure, the RMR calculated by the Shedenbach equation in the ANrec group was significantly different from that obtained by the CI (CI: 1337.55+352.66; RMRShedenbach 1025.08+95.21; P= 0.003), that is, it led to underestimation of the TMR of patients with anorexia nervosa in the recovery phase. However, it proved to be adequate for the calculation of RMR in ANat patients. (RMR - CI = 978±133 kcal x RMRShedenbach = 781.98 + 46.80 kcal; P= 0.513). In general, there was a difference in the RMR estimated by the predictive equations between indirect calorimetry in AN patients. Conclusion: These results show the importance of not considering only weight and BMI as the only parameters for assessing the nutritional status of anorexic patients. Important changes in body composition were observed in recovered anorexic patients despite the normalization of BMI The evidence in the literature and the results mentioned in this research reinforce that PA can be a good marker of the alterations involved in this disease.