Mostly an issue with TPN, risk of death.
When a severely malnourished patient is given glucose, the following cascade of events takes place:
Insulin is released
this stimulates drive to produce ATP
As ATP is produced, phosphorus is depleted
As ATP is produced, the cellular Na/K ATPase is activated, leading to transcellular movement of potassium and eventually other electrolytes, including magnesium, phosphorus and calcium into the cell.
this leads to hypokalemia, hypomagnesemia, and hypophosphatemia.
Metabolic acidosis also develops.
Electrolyte abnormalities can cause prolonged QTc
Rapid phosphorus depletion can lead to hemolysis, hypotension, altered mental status.
this stimulates drive to produce ATP
As ATP is produced, phosphorus is depleted
As ATP is produced, the cellular Na/K ATPase is activated, leading to transcellular movement of potassium and eventually other electrolytes, including magnesium, phosphorus and calcium into the cell.
this leads to hypokalemia, hypomagnesemia, and hypophosphatemia.
Metabolic acidosis also develops.
Refeeding syndrome
Fluid overload
Starvation ketoacidosis
Insulin secretion
Diabetic ketoacidosis 
Loss of myocardium
Diabetic ketoacidosis
Na absorption