Hidden Adiposity Beyond BMI: Body Composition and Lifestyle Profiles Among Sport Sciences Students at Universidad Técnica del Norte, Ecuador

Background/Objectives: Body mass index (BMI) is widely used to assess weight status but does not directly characterize body composition. Lifestyle assessment may provide complementary behavioral information. This study examined BMI–body-fat classification discordance and compared body-composition and lifestyle profiles across operational adiposity phenotypes among sport sciences students at Universidad Técnica del Norte, Ecuador. Methods: An analytical cross-sectional study was conducted in a non-probability convenience sample of 303 students enrolled in two sport sciences degree programs. Body composition was estimated by bioelectrical impedance analysis using the InBody 270, and health-promoting lifestyle behaviors were assessed using a 52-item Spanish-language adaptation of the Health-Promoting Lifestyle Profile II (HPLP-II). Elevated body fat was defined using sex-specific operational criteria (>20% in men and >28% in women). BMI classification performance and differences in body-composition and lifestyle characteristics across phenotypes were analyzed. Results: Elevated body fat was identified in 53.5% of participants, and 19.5% met the operational criterion for hidden adiposity. Among participants with normal BMI, 32.1% had elevated body fat. Relative to the operational BIA-based criterion, BMI showed 63.6% classification agreement for elevated body fat and a 36.4% false-negative rate. Participants with hidden adiposity showed lower muscle-related indicators and lower scores in physical activity, health responsibility, and stress management, although lifestyle-related effect sizes were generally small. Conclusions: Combining BMI with BIA-derived body-composition estimates revealed classification discordance not captured by BMI alone. Selected HPLP-II domains also differed between phenotypes, although effect sizes were small. These findings describe an operational body-composition phenotype and should not be interpreted as evidence of clinical obesity or metabolic disease.