Kwashiorkor

A 2-year-old child from a low-resource setting presents with generalized swelling, lethargy, and hair color changes over 2 months. The child was breastfed until 18 months, then transitioned to a diet predominantly of corn gruel and starchy carbohydrates with minimal protein. On examination, the child shows the clinical picture marked **B** in the diagram: bilateral pitting edema, sparse hair with alternating light and dark bands (flag sign), flaky desquamating skin over pressure areas, hepatomegaly, and apathy. Laboratory studies reveal severe hypoalbuminemia (1.8 g/dL), low transferrin, and low prealbumin. Which of the following best explains the pathophysiology of the edema in this condition?