Chemical changes in body in starvation

Starvation usually implies complete deprivation of food, water only being supplied. The causes can be manyfold, e.g. famine, political protests, lesions of esophagus and stomach etc. Total lack of food can even result death if body is deprived of food for few months. A person who is thin will suffer issues much earlier than fatty person. Women tolerate starvation better than men because of more fat in their bodies.
The following changes are found to take place during starvation:
Weight Changes
If a person does not ingest any calories, still his caloric expenditure continues, he will be in a condition of a negative energy balance and will gradually lose weight.
If a body is deprived of food, first the adipose tissue is utilized for energy for the body and then the other organs if the body is starved for long time. The extent to which different organ lose weight in starvation varies markedly. The adipose tissue may completely disappear while the liver, muscles and gastrointestinal tract may lose about one-third of their mass. The heart size is also diminished. But the central nervous system loses only 5% of its mass.

Carbohydrate Metabolism

Following alterations in carbohydrate metabolism are seen in starvation:

  1. The liver glycogen falls very rapidly to a very low value. Later this lowered liver glycogen level might show some recovery due to gluconeogenesis. The muscle glycogen also shows fall but to a lesser extent than liver glycogen.
  2. Blood glucose level remains normal for the first two days but then falls to a level as low as 50 mg%. Blood glucose may again show a rise due to an increased gluconeogenesis.

Fat Metabolism

After carbohydrate reserves have been utilized, the fatty acids are mobilized from the fat depots. An excessive production of ketone bodies results in ketosis. Fatty liver results due to deposition of neutral fat. The liver phospholipids are decreased.

Protein Metabolism

A negative nitrogen balance occurs because the subject continues to catabolize body proteins in the absence of protein intake. The deamination of amino acids continues and the resulting NH3 is converted to urea while the non-nitrogenous residue is converted to either glucose of acetyl-S-CoA.

The metabolism of proteins in starvation is shown by a study of the urinary N in the fasting person. The excretion of 1 gram of N in the urine represents the breakdown of 6.25 grams of tissue proteins. In the fast ending in death there are five stages associated with different amounts of N excretion in the urine.

These stages are given below:

  1. For the first 1 or 2 days, a low urinary N is seen because the body derives most of the energy from its carbohydrates reserves.
  2. Later the urinary N rises reaching a maximum on the third or fourth day. This is due to the utilization of the reserve protein present mostly in the liver, alimentary tract, thymus, pancreas, kidneys and spleen.
  3. After the stage of an increased urinary N there occurs a progressive fall in urinary N which may fall to about 6 grams per day, representing the breakdown of 6 x 6.25= 37.5 grams of tissue protein per day. During this stage the body is utilizing fats for deriving calories. The respiratory quotient (R.Q) in this stage may fall to near 0.70.
  4. After the fat reserves are exhausted, urinary N again show rise showing an increased breakdown of tissue proteins.
  5. Finally renal failure sets in and the urinary N may again fall. This occurs just before death. However, it must be realized that a fasting person does not necessarily pass through all these above mentioned stages before he dies.

Urinary Excretion of Non-proteins Nitrogenous Products During Starvation

  1. Urea: There is an initial increase in urea excretion; later urea excretion falls and remains below the normal.
  2. Ammonia: As ketosis develops, the NH3 excretion rises. Ammonia production in the general tubules helps in regulating blood pH and also conserves Na.
  3. Creatinine and creatine: There is a fall in creatinine excretion but creatine excretion increases. The creatinine-creatine excretion remains nearly unchanged.


Under-nutrition or semi-starvation occurs much more frequently than total starvation and is found whenever there are famines, wars and extremely poverty. It may also occur in certain diseases, e.g. diseases of the gastrointestinal tract, anorexia nervosa, cancer and prolonged infections. The diet is low in calories but is also usually deficient in vitamins and essential minerals; multiple deficiencies are therefore present. The clinical picture may vary markedly.
Pure under-nutrition (a decreased intake of calories only) results in the following clinical pictures:

  1. The body weight is low. The weight loss involves chiefly body fat but some loss of tissue proteins may also be present. The condition called emaciation is observed. There is atrophy of the musculature. The individual show prominent ribs, winged scapulae, spindly arms and legs and flat buttocks. The skin is dry and inelastic. The loss of body weight may be masked by water retention and in some cases gross edema may also be present.
  2. There is a decrease in all metabolic activities. There is a reduction in the cardiac work, a low blood pressure and subnormal body temperature. All these factors contribute to the fall in the subject’s Basal metabolic rate (BMR).
  3. Easy fatigability is present and the person avoids all types of exertion.
  4. The subject feels constant hunger. He suffers from spells of dizziness.
  5. Resistance to tuberculosis is decreased and there is a greater incidence of this disease in uder-nourished populations. However, there is a decreased incidence of hypertension and diabetes mellitus.
  6. Typical psychological changes such as moral deterioration, mental apathy and depression are usual. The intellectual capacity and work productivity are decreased. The person feels and looks older than his actual age.