Severe early childhood caries (S-ECC) is an acute type of dental caries that has adverse effects on the quality of nutrition and growth of children by causing pain and discomfort. The present study was conducted to investigate the relationship between severe early childhood caries and body mass index (BMI) in children. In this descriptive study, 401 systemically healthy children were randomly selected. After completing the questionnaire, height, weight, and DMFT indices were recorded and examined in terms of the relationship between BMI and S-ECC. The chi-square test and logistic regression were used to analyze the data. In total, there were 188 people with s-ECC and 213 healthy people. In addition, in terms of body mass status, 28.1% were overweight, 38.1% were normal, 13.7% were underweight, and 19.7% were obese. The average DMFT of the statistical population was 3.5 and the average age of the statistical population was 4.7 years. Based on data analysis, the variables of age, consumption of milk at bedtime, BMI status (obesity and underweight), and consumption of snacks had a significant and direct relationship with the occurrence of s-ECC (p < 0.001). According to this study, there is a positive correlation between s-ECC and obesity and underweight based on the Centers for Disease Control's BMI chart.
