Kidney transplantation is the greater renal replacement therapy and, compared with dialysis,is associated with better quality of life and reduced costs over time. However, it is well known that significant weight gain and obesity are very common after kidney transplantation, mainly during the first year after transplant. Besides, obesity is a risk factor for the development of cardiovascular complications, new-onset diabetes after transplantation and it is associated with graft loss. The use of immunosuppressive medications, the break of dietary restrictions associated with dialysis period and improvements in appetite are acceptable causes for weight gain. However, there is a lack of evidence for effective nutritional interventions to prevent weight gain after kidney transplant.

In this context, it is well known that high-protein and low glycemic index diets are effective for body weight loss and subsequent weight maintenance. Moreover, protein generally exerts a better satiety effect than carbohydrates and lipids. So that, considering that there is a need to develop effective interventions to minimize the negative impact of weight gain and obesity on kidney transplant outcomes, a randomized clinical trial, that evaluate the effect of a high protein and low glycemic index diet (as a nutritional intervention) is likely to be effective in preventing weight gain after kidney transplantation.

This study is a randomized clinical trial, which will follow and evaluate kidney transplant recipients during one year after transplantation. There will be two groups: a control group (60 patients) and the intervention group (60 patients). The dietitian visits will happen monthly at the first six months and twice in the last six months. The study assessments (weight, anthropometry, body composition and biochemistry) will be performed during these visits. Potential participants will be identified during their initial two months following transplantation. Eligible transplant recipients will be invited to participate, given detailed information about the trial and, if agreeable, will be asked to provide written informed consent. Participants will be randomized to receive either nutrition intervention with a high-protein and low glycemic index diet or an standard nutrition protocol. This randomization will be performed by a statistical consultant using randomization.com site. The length of the study will be 1 year for each patient, so that the assessment of anthropometry, including measures of weight (monthly) and body composition (every three months) will be performed by one specialist renal dietitian. Laboratory staff will perform all laboratories testing, including serum and urine creatinine (monthly), glycemia, cholesterol, HDL-cholesterol, triglycerides, glycated hemoglobin and uric acid (each three months), high-sensitivity C- reactive protein (baseline and 6th month) and 24-h urine test with albumin, protein, creatinine and urea excretion (every three months for intervention group and at baseline, 3rd, 6th and 12th month for control group). Demographic and clinical data will be assessed at the first dietitian visit. Body weight and height of patients will be obtained and body mass index (BMI) (kg/m2) will be calculated. Waist circumference will be measured midway between the lowest rib margin and the iliac crest, with flexible, nonstretched fiberglass tape. This evaluation will be made every visit (monthly in the first 6 months and twice in the last 6 months). Body fat percentage (assessed each three months) will be measured by using tetrapolar bioimpedance and basal metabolic rate will be evaluated by indirect calorimetry at baseline and 6 months later. All the anthropometric assessment will be performed with the patient fasting, wearing light clothing, without contact with metals and without shoes. The prescription of the diet will be calculated by using nutritional table by software version. It will be considered 1,3g /kg/day of protein and the glycemic index will be estimated with glucose as standard food. Energy intake will be assessed by a 24-h recall on the day of each dietitian visit by the research dietitian. Diet composition also will be analyzed by using nutritional table by software and will be made in every visit. Satiety levels will be assessed each three months for intervention group and only at baseline for control group by using a visual analogue scale of appetite.