Overweight and obesity, particularly increased total and/or abdominal fat mass (FM), are strongly linked to the development of cardiovascular diseases. Managing obesity effectively requires lifestyle and dietary modifications, including increased physical activity. Among the various exercise strategies, Moderate-Intensity Continuous Training (MICT) and High-Intensity Interval Training (HIIT) are widely recommended for reducing FM. Compared to MICT, HIIT is a time-efficient approach, often perceived as more enjoyable, and has been shown to promote greater total and abdominal fat loss in a shorter period. However, the precise mechanisms underlying this enhanced fat loss remain unclear. This study aims to compare the acute effects of two isoenergetic exercise sessions - MICE (Moderate-Intensity Continuous Exercise) and HIIE (High-Intensity Interval Exercise) - on key physiological responses involved in fat mass loss. Specifically, we will assess plasma catecholamine levels during exercise and recovery, as well as oxygen consumption, substrate oxidation, and appetite over the 2-hour post-exercise period in young females with overweight or obesity. By elucidating the role of catecholaminergic stimulation as a potential regulator of fat mass loss, this research could provide valuable insights for optimizing exercise strategies in weight management and metabolic health.