Effect of Nutritional Intervention and Olive Oil in Severe Obesity

After enrollment, patients undergo a diagnostic phase (baseline) with nutritional, anthropometric and body composition assessment (multifrequency bioelectrical impedance analysis and dual X-ray absorptiometry); investigation of clinical history; collecting blood samples; carotid artery intima-media thickness, heart rate variability and accelerometry assessments; and application of validated questionnaires to evaluate secondary outcomes. Patients will be randomized into three different treatment groups. Randomization will be stratified according to Body Mass Index (BMI) (BMI between 35 and 39,99 kg/m2 and BMI ≥ 40 kg/m2), allocation ratio 1:1:1 and parallel intervention. Then, trained nutritionists will deliver the intervention according to the patient group and they will be followed-up for 12 weeks, with visits each 4 weeks. Interventions will be provided as follow: Olive oil group: in order to evaluate the effect of only the extra virgin olive oil on primary and secondary outcomes, patients will be instructed to maintain habitual food consumption and consume 52 mL of extra virgin olive oil daily (4 sachets per day, 2 at lunch and 2 at dinner). Nutritional intervention group: patients assigned to this group will receive nutritional intervention consisting of prescription of individualized food plan to reduce 5 to 10% of initial body weight, nutritional counseling for comorbidities and promoting healthy eating habits and physical activity. Resting Energy Expenditure (REE) will be calculated according to Horie-Waitzberg \& Gonzalez equation developed for severe obese individual using current weight and lean body mass (Horie et al., 2011). Total energy expenditure (TEE) will be calculated multiplying REE by activity factor recommended by Institute of Medicine (Trumbo et al., 2005) and thermic effect of food (Hill, Wyat, Peters, 2012). Total energy value (TEV) of diet will be determined reducing 550 to 1100 kcal from TEE to reach 0.5 to 1.0 weekly weight reduction according to the patient's individual goal. Distribution of macronutrients will follow Dietary Reference Intake (DRI) recommendation: 45-65% of carbohydrates, 10-35% of proteins and 20-35% of lipids (Trumbo et al., 2002). Fat acids (FA) will be distributed as recommended by Sociedade Brasileira de Cardiologia (Sposito et al., 2007): ≤ 7% saturated FA, ≤ 20% monounsaturated FA and ≤ 7% polyunsaturated FA. Food plan prescription will distribute TEV in 4-6 meals. Motivation will be held to changing eating and lifestyle habits. Nutritional intervention plus olive oil: this group will receive conventional intervention plus supplementation of 52 mL of extra virgin olive oil daily (4 sachets per day, 2 at lunch and 2 at dinner). At the end of follow-up the same assessments performed at diagnostic phase will be held. To detect a reduction of 10 kg, with standard deviation of 30, which is in agreement with the study of Rodrigues e Silveira (2011), with a two-sided 5% significance level and a power of 80%, a sample size of 50 patients per group will be necessary, given an anticipated dropout rate of 42,9%. This research will be conducted at a capital of center Brazil, at Unidade de Pesquisa Clínica of Hospital das Clínica/UFG, Faculty of Medicine/UFG.