How do we replace the energy from the sugar we were previously consuming?

By consuming food high in fats and low in carbohydrates we create a state of ketogenisis, this is the process where by our bodies burn the fat from our food and in turn the fat stored in our bodies converting them to the necessary ketones required to keep our bodies at the optimal stasis for burning fat while still maintaining a good level of energy, by consuming foods like:
beef, venison, chicken, tuna, trout, flounder, scallops, eggs, cheese, butter and cream we provide our bodies with the required fats to create that ketogenic state.