BACKGROUND: Since the effects of supplements can be potentially harmful and/or ineffective to obtain desired positive benefits, there is a need to investigate supplementation to understand the responses of physiological systems, to educate consumers, and to provide feedback for businesses creating these supplements. The purpose of the current study was to test hemodynamic responses of a weight loss supplement and determine its effects on hemodynamic variables. METHODS: 31 participants underwent a randomized, double-blind, crossover study design and received a placebo or supplement on two separate days. Baseline measures of all variables were assessed prior to exercise. During exercise, each participant performed treadmill running at 80% VO RESULTS: There was a significant condition∗time interaction with the supplement having a higher PWV for the carotid to femoral segment (p=0.004). There were also significant condition∗time interactions for heart rate (p=0.001). Large arterial elasticity was significantly lower for the supplement (p=0.005). Systolic blood pressure was conditionally higher (p=0.001), as was diastolic blood pressure (p=0.003) and mean arterial pressure (p=0.003). Vascular resistance was conditionally higher for the supplement (p=0.044). CONCLUSIONS: Ingredients in the supplement caused multiple negative effects within hemodynamics and were ineffective at increasing running time.