Final answer:
The dietitian should use the patient's adjusted body weight to calculate the estimated calorie needs of a significantly underweight patient.
Step-by-step explanation:
The dietitian should use the patient's adjusted body weight to calculate the estimated calorie needs of a significantly underweight patient.
The adjusted body weight takes into account the patient's current weight and their desirable body weight. It may be calculated using the following formula:
Adjusted Body Weight = (Actual Weight - Desirable Weight) x 0.25 + Desirable Weight
Using the adjusted body weight provides a more accurate estimate of calorie needs for underweight patients, as it considers their current weight and the weight they should ideally be.