Effects of Different Dietary Interventions on Abdominal Fat Components, Quadriceps Muscles and Cardiometabolic Parameters

The study aims to evaluate the impact of different dietary interventions on abdominal fat components, quadriceps musculature and cardiometabolic parameters. This is a randomized clinical trial study conducted in overweight adults, selected by voluntary adherence, in an outpatient clinic of a cardiology hospital. The sample will take place by voluntary adherence, after evaluation of the eligibility criteria and signing of the Free and Informed Consent Form. The sample was calculated based on data from a study with the Brazilian population , with the sample size calculated calculated as a function of a mean difference between the initial visceral adipose tissue (VAT) concentration and after dietary intervention, obtaining a minimum sample of 100 individuals. To correct eventual losses, this number was increased by 20%, totaling a sample n of 120 individuals. Four dietary interventions will be applied: group with calorie restriction and balanced distribution of macronutrients (group 1), considering a progressive reduction of 500 to 1000 calories from the usual food intake or the recommendation of 20 calories/kg of current weight/day and distribution of macronutrients: 5% of carbohydrates, 2% of proteins and 3% of fats; group with calorie restriction and low-carbohydrate diet (group 2), considering a reduction in carbohydrate consumption and an increase in fat and protein intake, with the following proportions: 45% fat, 20% protein and 35% carbohydrate ; group with calorie restriction and low-fat diet (group 3), considering a restriction of fat consumption and an increase in carbohydrate consumption, with the following proportions: 20% fat, 15% protein and 65% carbohydrate and group with collective nutritional guidance (group 4), considering the recommendations of the Food Guide for the Brazilian Population. Patients will be followed up monthly for the first 6 months to assess weight loss, analyze adherence to the diet therapy plan, reinforce nutritional guidelines, and monitor anthropometric measurements, abdominal adipose tissue, quadriceps muscles, and biochemical parameters. A reassessment will be performed at 12 months to analyze weight regain, analysis of anthropometric measurements, abdominal adipose tissue, quadriceps musculature and biochemical parameters. The evaluation of VAT, subcutaneous adipose tissue (SAT) and quadriceps musculature by ultrasound will be performed at baseline and after 3, 6 and 12 months of intervention. The weight loss will be evaluated as a percentage (%), based on the difference between the weight at the outcome and the weight at baseline. The weight regain will be calculated considering the difference between weight at outcome (at 6 months) and weight after six months of completion of the dietary intervention (at 12 months from the start of the study). The following parameters will be monitored: blood pressure, biochemical tests (leptin, adiponectin, fasting glucose, fasting insulin, glycated hemoglobin, triglycerides, total cholesterol and fractions, and C-reactive protein), anthropometric measurements (weight, height, waist circumference, and abdominal circumference), demographic variables (age, gender, schooling) and socioeconomic status. Data will be analyzed using the Statistical Package for Social Sciences - version 13.0 . In the description of the proportions, the binomial distribution will be approximated to the normal distribution by the 95% confidence interval. The proportions will be compared by the Chi-square test. Student's t-tests for paired or Wilcoxon samples will be used to compare VAT, SAT, quadriceps musculature, weight, BMI and biochemical parameters before and after the intervention of each group. To compare the changes in VAT, SAT, quadriceps musculature, anthropometric and biochemical parameters between the intervention groups, the one way or Kruskal Wallis ANOVA test will be used. Statistical significance will be established when a p<0.05 value. The present study is expected to clarify the effects that different dietary interventions produce over 3, 6 and 12 months on weight, abdominal fat deposits, quadriceps muscles and cardiometabolic parameters.

Inclusion criteria

• Individuals of both sexes, aged ≥20 years, Body Mass Index (BMI) ≥25kg/m², attended at the general Nutrition outpatient clinic of a public university hospital reference in cardiology.

Exclusion criteria

• Malnourished and eutrophic individuals;
• Individuals with liver disease and/or splenomegaly, ascites, or with recent abdominal surgery;
• Pregnant women and women who had children up to 6 months prior to the survey screening;
• Individuals with consumptive diseases whose weight loss may be a consequence;
• Individuals with hypothyroidism or hyperthyroidism, on pharmacological therapy for weight loss and/or on hormone therapy;
• Individuals with mental or psychological illnesses that may make it difficult to understand dietary guidelines;
• Individuals with physical limitations that made it impossible to carry out the anthropometric and abdominal adipose tissue evaluations.