A Multicomponent Family Treatment of Childhood Obesity Based on the Planetary Healthy Diet: A Randomized Controlled Trial

The Planetary Health Diet (PHD), recognized as a healthy and environmentally sustainable dietary pattern, has been promoted globally; however, its role in supporting weight change among children within structured weight management interventions remains unclear. A four-month randomized multicomponent family-based trial was conducted with 120 dyads of children with obesity (7-12 years) and their guardians. The intervention group (IG) received counseling on the PHD, portion size reduction, and strategies to increase moderate-to-vigorous physical activity, while the control group (CG) received general guidance based on the Dietary and Physical Activity Guidelines for the Brazilian Population, emphasizing the avoidance of ultra-processed foods. Dietary intake was assessed using a food frequency questionnaire, and anthropometric measurements were taken by trained professionals at baseline and during each consultation. Mixed-effects models were used to estimate BMI change in children and guardians. Most guardians were mothers with low-to-middle income. Attrition was around 40% in both groups, but most participants were followed up for four visits. No significant difference in BMI variation was observed between allocation groups; however, both groups of children reduced BMI (IG = -0.2 and CG = -0.4; <i>p</i> = 0.002), with no change among guardians. PHD adherence scores changed minimally overall, but consumption of nuts and fruits increased in both groups. Although the intervention did not outperform the control in reducing BMI, the overall BMI reduction among children in both groups suggests that participation in a lifestyle-focused trial, regardless of specific content, may promote weight management in children with obesity.