While gonadal axis dysregulation due to energy deficit is well recognised in women, the effects of energy deficit on the male gonadal axis have received much less attention. In this presentation I will cover the effects of energy deficits (both absolute and relative) on the male gonadal axis, highlighting the role of excessive exercise (i.e., Relative Energy Deficit of Spoert (RED-S), from a clinical and mechanistic perspective, provide recommendations for management, and highlight knowledge gaps and opportunities for future research.