lol @ benz and Lori if you really think supplements don't work then you may not be taking good quality supplements.
In an average Americans diet many deficiencies exist...yes if we ate more raw foods, truly organic foods that haven't been sprayed with pesticides and handled poorly, got enough good vegetables, grains and meats we may not need supplements but that really never happens. Most people are deficient in their B vitamins...this group of vitamins is essential and when missing can lead to a number of problems: headaches, migraines, dermatitis, lack of energy, high blood pressure, anemia, auto immune diseases, the list goes on and on...another major deficiency is Omega 3 (6 and ) as well but primarily 3, when we cook our foods the good fats break down so even eating fish, if cooked, may not be reap the benefits you think it does...this deficiency leads to another list of problems...so supplementing for even clean good eaters is normally a safe and smart thing to do.
Now onto Carnitine-carnitine helps your body transport and break up long chain fatty acids and burn them for energy. One my diet I do not eat a lot of red meat and no dairy products which are the most abundant sources of carnitine...there is a very limited amount or no carnitine at all in white meats and many vegetables. So to cover this potential deficiency in my mind is quite important, especially considering what carnitine does in the body. So could I personally be low in carnitine which is why when I take it I feel more energy? Probably so.
BTW I have no idea why you think there is a difference in the way it works between males and females.