L Carnitine is Underrated. New Meta Review Reminds Us Why. Carnitine Deficiency: What You Need to Know The Medical Biochemistry Page Carnitine has a central role in fat metabolism. During the overnight fasted state and in exercise performed at low to moderate intensity, long chain fatty acids serve as the primary energy source for Meet L Carnitine a naturally occurring amino acid that plays a key role in helping the body convert fat into usable energy. It works by transporting fatty acids into your cells to