Introduction: An increase in childhood body mass index is a strong predictor of adult obesity. A key risk factor for childhood overweight is a lack of breastfeeding.
Objective: This study was conducted with the aim of investigating the relationship between breastfeeding pattern and body mass index of children in military families.
Materials and Methods: In this descriptive-analytical study, 279 children aged 2 to 5 years were examined using the full number method. The study took place at armyaffiliated kindergartens in Tehran in 2021. Data was gathered through a researcherdesigned questionnaire, along with height and weight measurements to calculate body mass index. Analysis was carried out using SPSS software version 22 and relevant statistical tests.
Results: The children had an average age of 4.63±1.12 years and an average body mass index (BMI) of 15.45±2.06. While most children (70.9%) were exclusively breastfed, there was no significant correlation observed between BMI and feeding method. However, children exclusively breastfed had lower BMI on average compared to those on formula or mixed nutrition. 
Conclusion: The relationship between obesity and various factors, such as environmental and genetic traits, is complex. Factors from early life, like nutritional patterns, birth weight, and exclusive breastfeeding duration, alone may not reliably predict childhood or postnatal obesity incidence. Therefore, further research on childhood obesity and related factors, especially within the first year of life, is recommended.