In obese adults undergoing yellow fever immunization, a protein-sparing modified fast supplemented with 100 grams of glucose induces a greater increase in insulin and glucose concentrations and a greater suppression of ketone bodies compared to a protein-sparing modified fast without glucose supplementation.

When glucose is consumed during a protein-only fast, the pancreas releases a large amount of insulin. This insulin stops the body from breaking down fat for energy, which reduces ketone production. At the same time, the infection triggers the pancreas to release more glucagon to keep blood sugar stable, but only when glucose is present. Without glucose, glucagon rises differently, but with glucose, the body uses insulin and glucagon together to manage energy supply during infection.