going straight to the point, 5-HTP (5-hydroxytryptophan) is a precursor of the neurotransmitter serotonin. The amino acid tryptophan is converted to 5-HTP which in turn gives rise to serotonin. 5-HTP is found in the seeds of the African plant Griffonia Simplicifolia.
Serotonin is a neurotransmitter that exhibits several functions such as: control of the release of some hormones and regulation of circadian rhythm, sleep and appetite. Serotonin also produces an inhibitory effect that soothes and promotes a feeling of contentment and satiety. That is to say, it ends up in a way by removing the hunger of those who can not stop eating and ends up gaining weight because of it.