Final answer:
During pregnancy, a 25-year-old female can expect to see an increased energy requirement, starting with no additional caloric needs in the first trimester, to an additional 300 calories per day during the second and third trimesters to support the growing fetus.
Step-by-step explanation:
The amount of energy used by a 25-year-old female during pregnancy can be expected to increase as the body adapts to support the growing fetus. Initially, during the first trimester, the caloric needs may not significantly increase, and a weight gain of about 0.45 kg (1 lb) per month is normal. During the second and third trimesters, there is an increase in appetite, but only an additional 300 calories per day are necessary to support fetal growth. This results in an average weight gain of 0.45 kg (1 lb) per week.
Besides caloric intake, overall weight gain during pregnancy is not solely from fat storage (approximately 2.3 kg or 5 lbs), but also includes the weight of the fetus, enlarged uterus, amniotic fluid, and placenta, as well as increased blood volume and breast tissue. It is important for expectant mothers to understand that doubling their caloric intake is likely to lead to excessive weight gain which can have negative implications for both mother and child, including the risk of developing diabetes and obesity later in life.