28. Partial starvation, accelerated forms of energetic insufficiency – anorexia nervosa. Refeeding

Introduction

In partial starvation is the process of starvation repeatedly interrupted by small food intake, however this isn’t sufficient to provide the normal number of calories. In the long run is the intake of calories too low, however it may still be enough for stabilization of body weight, as the metabolic rate can continue at a lower level to allow survival. Unlike in complete starvation will vitamin and mineral deficiencies have time to develop during partial starvation.

Partial starvation occurs as an everyday phenomenon in the 3rd world, among homeless people and in poverty. Concentration camps and POW (prisoner-of-war) camps are also good examples, although not as relevant nowadays. Partial starvation can occur in any part of the world in cases of various pathological states like anorexia nervosa, GI diseases, hyperthyroidism, chronic inflammation, cancer etc.

The biochemical changes are similar to those of complete starvation, except that the repeated nutrient intake delays utilization of body stores of calories. Intake of carbohydrates and proteins prevents deadly breakdown of proteins in the late, adapted phase but instead “lock” the patient in this phase chronically. The BMR decreases by up to 30% due to decreased T3 and T4, and the resting body temperature may be lower than normal.

Aetiology

There can be many causes for partial starvation. Decreased feeding can occur in 3rd world countries and anorexia nervosa. In diabetic glycosuria are large amounts of caloric-rich glucose lost. In cancer and hyperthyroidism is the metabolic rate very high. Anorexia occurs as a symptom of diseases like congestive heart failure and COPD. Elderly may have problems with dentures, low appetite, decreased sense of taste and poverty, all of which can lead to partial starvation.

Congestive heart failure leads to partial starvation by multiple mechanisms. The backwards congestion affects the liver and GI tract, causing malabsorption, maldigestion and anorexia. The forward failure periodic low cardiac output causes fatigue, which may decrease food intake. Low CO also promotes anaerobic glycolysis, which is less energy-efficient than aerobic glycolysis. Partial starvation causes protein breakdown of the myocardium, which further worsens the heart failure.

A similar pattern can be seen in COPD. In COPD is the work of breathing increased, which increases the energy requirement of respiratory muscle. There is also dyspnoea, which can cause issues with feeding. Partial starvation causes protein breakdown of the respiratory muscles, which worsens the respiratory failure which further increases work of breathing.

Consequences

Muscle, fat and visceral organ mass decreases. BMR, physical working capacity and body temperature all decrease. The cold tolerance is poor. The mental performance is impaired. Heart rate, blood pressure and cardiac output decrease. Breathing is shallower, so alveolar ventilation is decreased. The fat content of the liver increases, which may impair liver functions.

In the GI tract atrophy of the villi develops, causing malabsorption. The exocrine pancreas is deficient, causing maldigestion. Starvation-induced oedema develops by unknown mechanism.

Endocrine dysfunctions occur. FSH and LH are low. Osteoporosis occurs. The resistance against infection decreases, predisposing to respiratory and GI tract infections.

Refeeding

When refeeding after starvation it’s important to do it correctly. Failure to do so will cause refeeding syndrome, a syndrome of metabolic disturbances. Refeeding syndrome occurs when starved people are re-fed with carbohydrates too quickly.

Starved people switch from predominantly carbohydrate metabolism to fat and protein metabolism. During this period will the amount of minerals inside cells be much lower than normal, despite normal serum concentration of these minerals.

During refeeding will the elevated blood sugar lead to increased insulin and decreased glucagon secretion. This stimulates glycogen, fat and protein synthesis. These processes require minerals such as phosphate and magnesium, as well as vitamins like thiamine. Insulin stimulates the uptake of potassium into cells, and phosphate and magnesium also enter the cells. This rapidly decreases serum levels of these three minerals. Hypophosphataemia, hypokalaemia and hypomagnesaemia predispose to potentially deadly effects like heart failure, arrhythmias, muscle spasms and coma.

To prevent refeeding syndrome should starved patients start with a low level of energy replacement, and vitamin supplementation should be given. Electrolyte and fluid imbalances should be corrected during refeeding.

Accelerated starvation

There are some conditions where the starvation can be accelerated beyond the normal rate. Many medical conditions, like trauma, tumors and postoperative states can cause accelerated starvation simply because they both cause low food intake and high metabolic rate.

In pregnancy will the foetus function as a parasite; it takes everything it needs from the maternal circulation even if the mother is starving. If the mother is starving will ketone bodies and hypoglycaemia cause damage to the foetal brain.

Alcohol intoxication also accelerates starvation. Patients affected by this usually vomit and are undernourished. Alcohol inhibits gluconeogenesis, which is essential for maintenance of body functions during starvation.


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27. Complete starvation. Occurrence and process.

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29. Protein deficiency. Protein-calorie malnutrition. Senile sarcopenia

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