Most of the fatty acids come from triglycerides or phospholipids. Fatty acids are important sources of fuel in the body because they produce large quantities of ATP when metabolized in the body. Though most cell types can use either glucose or fatty acids for energy generation, while long chain fatty acids can’t transport the blood-brain barrier (BBB) and can’t be used as energy source for central nervous system. However, short-chain fatty acids and medium-chain fatty acids can transport across the blood-brain barrier (BBB) and enter the brain and act as an alternative energy source to ketone bodies.