Objective To explore the difference of body composition in infants under different nutritional status, so as to provide evidence for nutrition and health evaluation of infants.

Methods A total of 2 307 infants who received health examination at Liuzhou Maternity and Child Healthcare Hospital from September 2020 to December 2022 were recruited as study subjects. They were divided into different groups based on various months of age and nutritional status (wasting, normal, overweight, obesity). The indicators of body composition under different gender, age and nutritional status were compared between groups.

Results The body length, body weight and body mass index (BMI), lean meat mass and total water content of boys were higher than those of girls (all P < 0.05), while the fat mass, nutrient index, basal metabolic rate (BMR) and body fat index of girls were lower than those of boys (all P < 0.05). Fat content of girls increased with age (P < 0.05), while there was no age difference of boys (P > 0.05). BMI, predictive index, and body fat index of both boys and girls decreased with age (P < 0.05), while lean meat mass, total water content, and BMR of them increased with age (P < 0.05). There were significant differences in fat content, lean meat mass, total water content, BMR, and BMI between boys and girls under different nutritional states (all P < 0.05). Changes of prediction index and phase angle were not associated with their nutritional status (all P > 0.05).

Conclusion The body composition indexes of infants are different in different gender, age group and nutritional status. The analysis can provide evidence for predicting the occurrence of nutritional diseases such as obesity and malnutrition, and early development of intervention strategies and nutritional guidance.