Carbohydrate are essential for the metabolism of Fat.
*For complete oxidation of fatty acids , we need oxaloacetate. Fatty acids are broken down in to Acetyl CoA by beta oxidation. For oxidation to occur it needs oxaloacetate which is derived from carbohydrate metabolism.
* If carbohydrate ids deficient , then oxaloacetate which is generated is diverted to gluconeogenesis. Thus there will be less Oxaloacetate available for TCA cycle, and Acetyl CoA cant be fully oxidized. *Thus there will be accumulation of Acetyl CoA and it will be directed to ketogenesis. *Also carbohydrates provide glycerol-3-phosphate through glycolysis.
*Without carbohydrates, fatty acids cannot be properly stored as triglycerides.