Causes
The causes of the experience of body load are unknown. However, one proposed mechanism is the stimulation of serotonergic 5-HT receptors, particularly those involved in tactile sensation and, equally importantly in many cases where nausea is experienced, those located along the lining of the digestive tract. Serotonin is heavily involved in appetite control, and over-stimulation of serotonergic receptors has been shown to cause nausea in overdoses of SSRIs or MDMA. Many psychedelics which can cause body load are partial serotonin agonists, which work by mimicking the structure of serotonin to varying degrees.
Read more about this topic: Body Load