In this article, the effects of food starvation will be discussed. Starvation induces a number of metabolic changes, some occurring within a few days. There is a progressive fall in B.M.R, body temperature, pulse rate and blood pressure. Ketosis develops and some retention of salt and water occurs.
Total starvation includes complete deprivation of water, salts and food. It results death of the animal in the shortest possible time. Deprivation of water only follows death of the animal in about a week, that of salts in two weeks, whereas food starvation in about 3—4 weeks or longer. The length of time, a man can survive, depends upon the fat stores. The longest period of survival never exceeds 9 to 10 weeks.
Experimental Observations:
The effects of food starvation have been mostly observed in animals. But some direct observations on human beings have been carried out upon professional fasting men.
The following effects are seen:
General Condition:
During the first two days there is a craving for food, particularly at meal times. But later on this craving subsides, provided water and salts are freely allowed. Gradually the desire for food vanishes; weakness increases and a strong dislike undertaking any physical or mental effort develops.
At about this time the subject falls into a state of semi-consciousness. The pulse rate and the body temperature remain almost normal till before death. The sleep increases and respiration becomes slower. Temperature falls before death. The amount of urine as well as its urea content falls. Stool is formed and may be passed during or at the close of the starvation period.
Body Weight:
The body weight is steadily lost. The daily loss in man during the first ten days, amounts to between 1 — 1.5% of the original body weight. At the onset of the fast the fat depots and subcutaneous tissue bear the brunt. The extracellular fluid in large quantity is also lost. Dissolution of the muscular tissue and protoplasmic structure occurs later. The muscle fibres are much reduced in size and many of the fibres are degenerated.
The muscles lose about 35% of its weight. The brain and heart lose about 3% of their weight. Kidney loses about 20%, the liver loses about 55%, and the spleen loses about 70% of their weight. Thyroid, adrenal and gonads lose about 2—6% of their weight. The organs and the tissues of the body are not affected alike. The more vital organs lose the least weight, whereas the less vital ones lose the most.
Metabolism of Carbohydrate, Fat and Protein:
During starvation, the body has to depend upon its own tissue materials. Of the three food stuffs—glycogen, fat and protein—the liver glycogen store is first mobilised. The protein, mobilised from stored protein in the tissue, is transformed into glucose (neoglucogenesis). This initial stage will last for not more than two days. In the next stage, 80—90% of the energy requirement will be derived from fats and the remainder (10—20%) from the proteins.
Since adipose tissue represents the largest amount of stored food, the second stage will last for the longest period—over two weeks. In the third stage, when the fat-store is almost exhausted, an energy requirement is derived from the breakdown of the body proteins. The cell substance will break up with a consequent dislocation of cell metabolism and cell life. This state of affairs, if continued, it will lead to death. The third stage lasts for less than one week.
Thus from the metabolic point of view, the whole period of inanition can be divided into three stages—the first stage is the stage of carbohydrate depletion, the second stage is that of fat depletion and the third stage is that of breakdown of body proteins. The determination of total R.Q. and of non-protein R.Q. will indicate the extent to which these three foodstuffs are burning at the three stages. The R.Q. is highest at the first stage and diminishes later on.
A brief description of the different metabolic changes is given below:
1. Carbohydrate Metabolism:
Carbohydrate store becomes almost depleted in the first two days. The blood sugar is maintained at a steady level even up to the end. This steady level is believed to be due to neoglucogenesis in the liver.
2. Fat Metabolism:
Fat which remains in adipose tissue (element variable) is utilised first. It goes into the liver where it is completely oxidised and an increased amount of acetyl coenzyme A is produced, resulting formation of ketone bodies whereas due to absence of carbohydrates, fat oxidation usually remains incomplete producing ketosis and acidosis.
Thus alkali reserve is diminished and various ill-effects of ketosis are produced. Ketones from the liver pass in to the blood and ketone bodies appear in the urine. The acidosis is compensated by bicarbonate of blood, increased pulmonary ventilation and increased elimination of CO2 from the alveoli, and increased ammonia formation in the kidney and excretion of ammonium salt in the urine.
3. Protein Metabolism:
Tissue protein is broken down and amino acids formed after hydrolysis constitute the ammo acid pool. The amino acids from this pool is utilised for the maintenance of the structural and functional efficiency of the vital organs. The amino acids also undergo deamination in the liver and the non-nitrogenous part helps in the maintenance of the blood sugar level.
The amount of nitrogen excretion during the first few days is directly proportional to the amount of protein intake before starvation. The average daily excretion in the first week is about 10 gm. During the second and third weeks the values are very low. But just before death (when proteins are rapidly breaking down) the urinary nitrogen rises (premortal rise). The end products of endogenous protein metabolism, i.e., creatinine, creatine, neutral sulphur compounds and uric acid are the main nitrogenous products.
Creatine excretion gradually falls as the weight of muscles diminishes. On the fifth day of starvation a man excretes 11.4 gm of nitrogen and the energy output is about 2,000 calories. 6.25 gm of protein when broken down eliminates 1 gm of nitrogen. The urinary nitrogen indicates 6.25 × 11.24 = 71.5 gm of protein catabolism. Thus the energy liberated at that amount of protein catabolism is 71.5 × 4.1 Cal = 300 calories. The rest of the calories are derived from fat, i.e., 190 gm of fat.
4. Mineral Metabolism:
Phosphorus and sulphur excretion in urine at first rises and then falls. The excretion of calcium is elevated and that of chloride, sodium, potassium and magnesium is reduced during starvation.
Changes in Blood and Urine during Starvation:
Blood Changes:
(a) Acidosis with diminished alkali reserve,
(b) Low blood sugar,
(c) Increased blood fats,
(d) Presence of ketone bodies, and
(e) Raised potassium (showing breakdown of tissue cells).
Urine Changes:
(a) Volume becomes less,
(b) Nitrogen content steadily falls,
(c) Presence of abnormal constituents like creatine, ketones, etc.
(d) Ammonia excretion increases as also the ammonia coefficient,
(e) Rise of acidity, and
(f) Fall of potassium that causes chlorine retention (Index of breakdown of tissues).
Premortal Changes:
The following changes indicate impending death:
(a) 50% loss of body weight,
(b) Rise of nitrogen excretion, and
(c) Fall of body temperature.