Background: Type 2 diabetes mellitus is associated with changes in body composition and muscle function. However, the relationship between body-composition parameters and deep core-muscle performance in younger and middle-aged adults with type 2 diabetes remains insufficiently explored.

Objective: To determine the association between body composition and core-muscle performance in adults aged 25–45 years with type 2 diabetes mellitus.

Methods: An observational cross-sectional study was conducted among 45 participants recruited through convenience sampling. Body composition was assessed using waist-to-hip ratio and a Karada bioelectrical impedance analyzer. Transversus abdominis and multifidus performance was assessed using a pressure biofeedback unit. Descriptive statistics and Spearman’s rank-order correlation were used.

Results: BMI was negatively associated with transversus abdominis endurance (ρ = −0.304, p = 0.042). Skeletal muscle mass (ρ = −0.425, p = 0.004) and subcutaneous fat percentage (ρ = −0.316, p = 0.034) were negatively associated with transversus abdominis strength. No statistically significant associations were observed between the other body-composition variables and transversus abdominis or multifidus outcomes.

Conclusion: Selected body-composition measures were associated with transversus abdominis performance, whereas no significant associations were found with multifidus performance. The findings should be interpreted cautiously because the study was cross-sectional and the pressure biofeedback unit provides an indirect pressure-based measure.