The Science of Carnitine: How It Works and Why It Matters The Role of l Carnitine in Mitochondria, Prevention of Metabolic Inflexibility and Disease Initiation If you're putting in the work but the scale isn't moving, your body might just need a little help tapping into its fat stores. That's where L Carnitine comes in. It's not a Are L Carnitine and L Carnosine the Same? Anti Aging Systems L carnitine is a naturally occurring amino acid structure that is made in the human brain, liver, and kidneys. L carnitine plays a critical role in energy production, as it converts fat into energy.