Does Vitamin C Increase the Body Heat Generated By The Nervous System?

The goals of this clinical trial are to determine whether or not vitamin C is able to: (1) increase the body heat generated by the sympathetic nervous system; and, (2) increase circulating vitamin D concentration during sympathetic nervous system stimulation in adult humans aged 18-40 years who meet the criteria for overweight based on body mass index. The main question it aims to answer are: 1. By how much does body temperature increase during stimulation of beta-adrenergic receptors when vitamin C is given. 2. By how much does circulating vitamin D concentration increase during stimulation of beta-adrenergic receptors when vitamin C is given. Participants will will be asked to: * undergo measures of body temperature * have blood sampled on two separate occasions: once during stimulation of beta adrenergic receptors, and once during stimulation of beta-adrenergic receptors while also been given vitamin C.