Undefatted meat causes a drop in blood levels of testosterone, the main androgenic (male) hormone, and therefore lowers rather than stimulates libido.
First of all, it promotes weight gain, and we know that heavier men have lower testosterone levels than leaner men. Secondly, it seems that a diet too rich in fats can, over time, interfere with the erection. This seems logical since it is known that too much lipid in the blood contributes to the obstruction of blood vessels, both those that irrigate the penis and make erections possible and those that do not. Arterial blockages are, more often than not, the primary cause of impotence.
First, rule out psychological causes, but then make sure your diet is rich enough in iodine, manganese, selenium or zinc.