RESUMEN
BACKGROUND: Clinical trials to treat childhood obesity show modest results, weight regain and high dropout rates. Children with obesity often live in families with habits that contribute to unhealthy weight gain. This study will test whether a family intervention with a Brazilian-adapted Planetary Healthy Diet (PHD) and reduced portion sizes, along with increased physical activity and reduced sedentary behavior, can reduce excessive weight gain. The protocol promotes the intake of in natura products and water and reduces ultra-processed foods, sugar, and sodium. It encourages family lifestyle changes and physical activities, with randomized allocation to experimental and control groups. The responsible family member will be evaluated during follow-up. The control group will receive a print of the Brazilian dietary guideline. METHODS: A factorial crossover design will also allocate families to receive reduced sodium salt plus anti-inflammatory herbs and a placebo salt. Both the control and intervention groups will be randomly assigned to the sequence of both salts. The approach aims to reduce body weight expectations and evaluate salt's impact on blood pressure. It includes a 1-month intervention, 1-month washout, and 1-month intervention with monthly clinic visits and teleservice by health professionals. The primary outcomes will be the variation in the Body Mass Index (BMI) of the children. BMI and the variation in the blood pressure of the pair (child/mother or father) as well as waist circumference (WC) and waist-to-height ratio (WHtR) will also be measured. DISCUSSION: The project will test the effectiveness of the use of the recommendations of the PHD, physical activity and a salt-reduced sodium. The results of the present study will allow the refinement of interventions aimed at the treatment of childhood obesity and may help develop guidelines for the treatment of obesity in Brazilian children. TRIAL REGISTRATION: The study is registered in the Brazilian Registry of Clinical Trials (RBR-10 mm62vs). Registered 10 February 2023.