Final answer:
During lactation, a mother's estimated energy requirement increases to meet the demands of producing milk. Additional calories are needed to ensure sufficient energy is available for milk production. Fat reserves accumulated during pregnancy can also contribute to meeting this increased energy requirement.
Step-by-step explanation:
During lactation, a mother's estimated energy requirement increases to meet the energy cost of producing milk. The efficiency of milk production is about 80%, meaning that for every 80 Kcal of milk produced, the mother needs to expend 100 Kcal. If a healthy baby needs 850 ml of milk daily, which is equivalent to 578 Kcal, the lactating mother will require an extra diet of approximately 720 Kcal per day to meet the demands of lactation. However, the fat reserves accumulated during pregnancy also contribute to meeting this energy requirement.