Acquisition of reproductive maturity involves one of the most important series of developmental events in an organism's life. The beginning of adolescence is marked by the onset of puberty. Puberty is the continuum of physical changes through which an infantile body matures into an adult capable of reproduction. This is a period of increased brain plasticity, where processes of re-wiring, neuronal proliferation, and pruning are enhanced. The initiation of mammalian puberty requires an increased pulsatile release of gonadotropin-releasing hormone from the hypothalamus. Puberty is regulated by neuroendocrine, genetic, and epigenetic factors. The maturation and function of the reproductive axis are highly sensitive to the energy status of the organism and sophisticated mechanisms exist to inhibit the axis in unfavorable energetic or metabolic conditions.In this review, we will focus on the impact of alcohol and obesity on reproductive outcomes, with emphasis on their effects on the timing of puberty. In the case of obesity, conflictive data are found, and while in females the association of overnutrition with advanced onset of puberty is consistent, in males, discrepant results have been reported. Concerning alcohol exposure, compelling evidence has documented a delay in the onset of puberty. We will present here data from both clinical studies and research involving preclinical models, which do not only delineate the impact of these conditions on the timing of puberty and potential underlying mechanisms, but that may help to define better strategies for the rational management of puberty disorders, especially of metabolic origin.