Final answer:
The nurse's most appropriate response would be that the patient's body has consumed his fat deposits for fuel because his calorie intake is lower than normal.
Step-by-step explanation:
The most appropriate response for the nurse to give to the family member is option B) His body has consumed his fat deposits for fuel because his calorie intake is lower than normal.
During the intermediate phase of recovery for burn patients, they may experience weight loss due to a decrease in calorie intake. The body will compensate for this by metabolizing stored fat as a source of energy. This is a natural process that occurs when the body's energy expenditure exceeds its calorie intake.
It's important to note that weight loss in burn patients is expected and can be a normal part of the recovery process. The nurse should reassure the family member that this weight loss is temporary and will improve as the patient's calorie intake increases.