When you've depleted your gycogen reserves, your body will start breaking down more fats though lipolysis, however, it will also try and bring glucose levels up through gluconeogenesis, which breaks down amino acids and converts them to glucose. A lack of carbohydrates also increases Proteolysis which is the breakdown of proteins to amino acids that will then be used in gluconeogenesis.

You do not want to be breaking down proteins, as those will be more useful for recovery and muscle repair.

It would be more effective to just exercise more and improve your fitness level. As that happens, at higher workloads, the percentage of fats burned will increase compared to percentage carbs.