This interventional study aims to evaluate the efficacy of a probiotics supplementation (Bifidobacterium longum subsp. longum Dipro-O and Bifidobacterium longum subsp. longum Dipro-X; dipro Gracfor PROBIOTICS FAST MELT) in treating childhood obesity and its impact on gut microbiota. The study will enroll 60 overweight or obese children aged 3 to 14 years. Participants will be randomly assigned to either a treatment group receiving lifestyle intervention combined with an oral Bifidobacterium preparations for 8 weeks, or a control group receiving lifestyle intervention alone. The primary outcome is the change in sex-specific BMI-for-age percentiles. Secondary outcomes include changes in height, weight, waist circumference, quality of life satisfaction, and alterations in gut microbiota composition analyzed via 16S rRNA gene sequencing.

Childhood obesity has emerged as one of the most serious public health challenges of the 21st century, with prevalence rates increasing dramatically worldwide. In China, the combined prevalence of overweight and obesity among children and adolescents has risen sharply over the past two decades, affecting approximately one in five school-aged children. This condition is associated with a range of adverse health outcomes, including metabolic disturbances, cardiovascular risk factors, and psychosocial complications, many of which can track into adulthood. Early intervention is widely recognized as critical for improving long-term health outcomes, underscoring the need for effective and sustainable therapeutic strategies. Growing evidence indicates that intestinal microbiota dysbiosis plays a key role in the pathogenesis of obesity. Studies have consistently reported alterations in the gut microbial composition of obese individuals compared to normal-weight controls, characterized by reduced microbial diversity and changes in the relative abundances of specific bacterial phyla. Specifically, a decreased proportion of beneficial bacteria such as Bifidobacterium and an increased ratio of Firmicutes to Bacteroidetes have been frequently observed in obese populations. These findings have spurred interest in microbiota-targeted interventions, particularly the use of probiotics, for weight management. Among probiotic strains, Bifidobacterium species have attracted considerable attention due to their potential to modulate host energy metabolism, reduce adiposity, and improve metabolic parameters. Preclinical studies in murine models have demonstrated that Bifidobacterium supplementation can attenuate diet-induced obesity by enhancing gut barrier function, reducing systemic inflammation, and regulating appetite-related hormones. However, despite promising preclinical evidence, clinical data in pediatric populations remain relatively limited, and the optimal strains, dosages, and treatment durations have yet to be definitively established. To address this gap, the present study is designed as a randomized, parallel-group, controlled clinical trial. It aims to evaluate the efficacy of a Bifidobacterium probiotics combination in overweight and obese children aged 3 to 14 years. The study specifically assesses the intervention's effects on anthropometric parameters, including body mass index (BMI) percentile and height, weight and waist circumference, and explores correlations between gut microbiota changes and clinical improvements. Participants will be randomly assigned to receive either lifestyle intervention combined with oral Bifidobacterium probiotics or lifestyle intervention alone for a duration of 8 weeks. The primary outcome is the change in BMI percentile from baseline to the end of the intervention period. Secondary outcomes include changes in height, weight, waist circumference, parental-reported quality of life satisfaction, and alterations in gut microbiota composition as assessed by 16S rRNA gene sequencing of fecal samples. By investigating both the clinical efficacy and the underlying microbiological mechanisms, this study is intended to support the development of evidence-based, targeted microbial interventions for childhood obesity.

Inclusion Criteria:

• Diagnostic Criteria (Refer to the "Expert Consensus on Diagnosis and Management of Childhood Obesity in China"): For children aged 2-5 years, refer to the "Growth Curve for Chinese Children and Adolescents Aged 0-18 Years" to determine the BMI cutoff points for overweight and obesity in Chinese children aged 2-5 years. For children aged 6-18 years, refer to the "Screening for Overweight and Obesity in School-Age Children and Adolescents" to determine the BMI cutoff points for overweight and obesity by age and gender in children aged 6-18 years.
• Age: 3-14 years.
• Fully informed consent: Parents or guardians have been fully informed of the clinical trial procedures, and both have signed the written informed consent form.

Exclusion Criteria:

• The child has chronic or severe systemic diseases.
• The child has a family history of obesity-related metabolic or endocrine diseases.
• The child has been diagnosed with psychological disorders or psychiatric diseases.
• The child has used antibiotics or probiotic preparations within 4 weeks prior to enrollment.
• The child was enrolled in other clinical studies 4 weeks prior to enrollment.