Sorry but for SOME people, eating fewer carbs really does lower their libido (for example, my hubby just found this out while doing the Carnivore diet with me which is basically zero carb). I think it isn't necessarily the low carbs but the fact that he's less hungry due to the ketosis and isn't getting as much energy overall and his body thinks he's starving. Reproduction is not a body priority when it thinks times are bad and food is scarce.