Relationship of fat mass index and fat free mass index with body mass index and association with sleeping patterns and physical activity in Saudi young adults women

Aim To analyze the association between Fat Mass Index (FMI), Free Fat Mass Index (FFMI), Free Fat Mass/Fat Mass (FFM/FM), and Body Mass Index (BMI) among young adult Saudi women and to explore how these body composition indices are associated with sleep and physical activity patterns. Methods A total of 1,741 university female students participated in this cross-sectional study. Body composition was measured using the InBody 270 body composition analyzer. FMI, FFMI, and FM/FFM were classified into tertiles (T1, T2, T3), with T1 classified as the lowest and T3 as the highest tertile. Sleep quality and duration were assessed using the Pittsburgh Sleep Quality Index, while physical activity was measured using an exercise vital sign tool. Results BMI increased significantly from Tertile 1 to Tertile 3 across all groups for FMI and FFMI (p < 0.001), while a decrease in FM/FFM was observed across tertiles (p < 0.001). Conversely, FFM was highest in the third tertile of FFMI (p < 0.001). No significant associations were found between sleep duration or quality and body composition indices, even after adjusting for age and BMI. However, significant associations were observed between physical activity frequency and duration and body composition, particularly FFMI and FMI. These associations became more pronounced after adjusting for age and BMI. Conclusion The findings highlight a strong association between physical activity patterns and body composition indices, particularly FFMI and FMI, among young adult Saudi women. While sleep patterns did not show significant relationships with body composition, the results emphasize the importance of regular physical activity in maintaining healthy body composition. These insights underline the need for targeted interventions promoting physical activity to support optimal health and well-being in this population.