Final answer:
The patient most at risk for protein-calorie malnutrition is 'C. An adult with a BMI of 17 kg/m2', as they are underweight, which suggests a greater vulnerability to conditions like kwashiorkor, a form of PEM.
Step-by-step explanation:
The patient with the greatest risk for developing protein-calorie malnutrition, also known as protein-energy malnutrition (PEM), would be C. An adult with a BMI of 17 kg/m2. This BMI value indicates that the adult is underweight and potentially has a marginal energy but insufficient protein intake. Underweight individuals, especially in the context of poor dietary diversity and inadequate protein sources, are more vulnerable to PEM, including conditions such as kwashiorkor and marasmus. Kwashiorkor is characterized by adequate calorie intake with insufficient protein consumption, often seen in developing countries among children and symbolized by a swollen abdomen due to edema. People with conditions that affect their ability to eat, such as vegetarians or vegans who may not consume adequate protein, or others avoiding certain food groups, may also be at an increased risk.