Comparing High-Intensity Functional Training and Resistance Training for Cardiometabolic Health in Overweight Adults: A 12-Week Randomized Trial

Physical inactivity and excess body fat remain major public health challenges, contributing to hormonal dysregulation and elevated cardiometabolic risk. High-intensity functional training (HIFT), widely popularized through CrossFit®, has been promoted as an efficient modality capable of eliciting broad physiological adaptations, yet its comparative health effects relative to structured resistance training (RT) are insufficiently understood. This randomized controlled trial compared 12 weeks of HIFT with periodized RT in 24 physically active but untrained adults to examine differential adaptations in endocrine markers, cardiovascular function, and body composition.Participants completed supervised HIFT or RT five times weekly. Pre- and post-intervention assessments included fasting hormonal biomarkers (growth hormone, insulin-like growth factor-1 [IGF-1], thyroid-stimulating hormone, leptin), blood pressure, plasma volume variation, and body composition. Both training modalities increased IGF-1 concentrations, whereas HIFT uniquely reduced leptin levels (−18.4%) and body fat percentage (−6.6%). HIFT also produced meaningful cardiovascular benefits, including lower diastolic blood pressure (−7.2%) and enhanced post-exercise plasma volume expansion (+88%), changes not observed in RT. Correlation analyses indicated that reductions in leptin were associated with decreased body fat following HIFT, while increases in IGF-1 correlated with reductions in diastolic blood pressure in the RT group.These findings demonstrate that, although RT effectively stimulates anabolic signaling, HIFT elicits broader and more integrated adaptations across endocrine, cardiovascular, and metabolic systems. For previously untrained adults, HIFT may therefore represent an efficient, multifaceted strategy for improving cardiometabolic health, with implications for scalable, community-based exercise interventions aimed at reducing chronic disease risk.