Answer:
First of all the glycogen stores of the body are slowly depleted (glycogen is a highly branched form of glucose and it is found mainly in the liver and the muscles). As the glycogen stores are used the body begins to break down fats (found in adipose tissue). The fats are converted to something called ketone bodies; these ketone bodies are used as energy for most tissues. This helps to conserve glucose for the liver and the brain. When the glycogen stores run out the body begins breaking down protein from the muscles of the body, it converts the carbon skeleton of each amino acid into glucose (which provides energy for the brain and liver only). This breaking down of muscle protein is what makes someone who is starving look emaciated. Of course if re-feeding does not occur then starvation ultimately results in death when there is no more sources of energy that the body can utilise.
Re-feeding is a complicated process; the patient must be fed little and often and given a diet high in fat and low in carbohydrates. As the days go on the meal frequency can be reduced and the amount at each meal can be slowly increased. Re-feeding syndrome is potentially fatal and so must be monitored. (Re-feeding syndrome is caused when the patient is given plentiful carbohydrates. It occurs when insulin causes cells to take up potassium and phosphates, this in turn causes swelling of the cells and therefore cell death)