Salmonids and more particularly rainbow trout are carnivorous species, and thus usually consider as glucose-intolerant (GI) species and poor user of dietary carbohydrates displaying a decrease in growth and a persistent postprandial hyperglycaemia when fish meal is substituted at more than 20% by digestible carbohydrates in the diet. Nevertheless, these findings were mainly deduced from experiments conducted on immature juvenile trout and only scarce data are available in sexually mature males and females. In this regard, we investigated the impact of a high carbohydrate diet (HC diet) on gametogenesis and reproductive performances of 2 year-old broodstocks fed with such a diet a whole year. Our results showed that both males and females ate and growth well when fed the HC diet even if, at the end of the trial, males, but not females, displayed growth retardation compared to control males. The glycaemia of fish fed the HC diet was higher than fish fed the control diet independently of the sex but these fish were not hyperglycaemic. Surprisingly, both sex displayed a precocious maturation. Whole body and gonads biochemical composition of fish did not differ during the whole year from one treatment to the other whereas liver of fish fed the HC diet retained more glycogen but less proteins compared to the control fish. We also monitored glucose metabolism modifications at the molecular level in both livers and gonads at different gametogenesis time points. Our results demonstrated that glucose metabolism strongly varied in female liver during gametogenesis independently of the diet whereas in male no significant difference where found. By contrast in both ovaries and testis, glucose metabolism related genes were found differentially expressed during gametogenesis but independently again of the diet. At spawning period, we performed cross-fertilization between groups. For the 4 groups, both fertilization and early developmental rate were equivalent from one group to the other. In overall, our results highlight strong but sex-dependent effects of a high carbohydrate diet on both oogenesis and spermatogenesis and a variation of glucose metabolism in both liver and gonads. However, these effects do not seem to affect reproductive performances.