23. Partial starvation, accelerated forms of energetic insufficiency - anorexia nervosa. Refeeding | Quizlet

Partial starvation?

The process of starvation is repeatedly interrupted by small food intake

= Is NOT sufficient to provide normal number of calories

Body weight can still be stabilized, as the metabolic rate can continue at a lower level to allow survival

Vitamin and mineral deficiencies in partial starvation?

They have time to develop in partial starvation, compared to in complete starvation

When can partial starvation occur?

Is an everyday phenomenon in 3rd world countries:

- Homeless people

- Poverty

- Concentration camps

Can occur in several pathological states:

- Anorexia nevrosa

- GI diseases

- Hyperthyroidism

- Chronic inflammation

- Cancer

Biochemical changes in partial starvation?

They are similar to those of complete starvation, except that the repeated nutrient intake delays utilization of body stores of calories

Intake of carbs and proteins prevents deadly breakdown of proteins in the late, adapted phase

In what phase are the partial starved patients?

They are "locked" in the late, adapted phase chronically

- BMR decreases by up to 30%, due to decreased T3 and T4

- Resting body temperature may be lower than normal

Etiology - partial starvation?

- Decreased feeding in 3rd world countries & anorexia nervosa

- Diabetic glycosuria - large amounts of calorie-rich glucose is lost

-Cancer/hyperthyroidism - metabolic rate is very high

- Elderly - problems with dentures, low appetite, decreased sense of taste

- Congestive heart failure

- COPD

Partial starvation in congestive heart failure?

Multiple mechanisms:

- Backward congestion affects the liver & GI tract (malabsorption, maldigestion & anorexia)

- Forward failure cause periodic low CO -> fatigue -> may decrease food intake

- Low CO also promotes anaerobic glycolysis - is less efficient than aerobic glycolysis

Partial starvation also causes protein breakdown of the myocardium -> further worsens the HF

COPD - how can it cause partial starvation?

Work of breathing is increased - increases energy requirement of respiratory muscles

- Dyspnoea -> causes issues with feeding

- Breakdown of respiratory muscles (to get protein) -> worsens the respiratory failure => increases work of breathing

Consequences of partial starvation?

- Muscle, fat and visceral organ mass decrease

- BMR, physical working capacity & body temp. decrease

- Cold tolerance is poor

- Mental performance is impaired

- HR, BP and CO decrease

- Breathing is shallower -> alveolar ventilation decrease

- Fat content of the liver increases -> may impair liver function

How are the abdominal organs affected by partial starvation?

GI tract: atrophy of villi develops -> malabsorption

Exocrine pancreas: Is deficient -> maldigestion

Starvation-induced edema develops by unknown mechanisms

Endocrinology in partial starvation?

Endocrine dysfunction occurs

- FSH and LH are low

- Osteoporosis occurs

- Resistance against infection decreases

= Predisposing to respiratory and GI tract infections

Reefeding after partial starvation?

After starvation, it is important to refeed correctly

- Failure to do this will cause refeeding syndrome

Refeeding syndrome?

Occurs when starved people are re-fed with carbohydrates too quickly

- Starved people switch from carbohydrate metabolism to fat- and protein metabolism

= The amount of minerals inside cells will be much lower than normal, despite normal serum conc. of these minerals

What happens during refeeding in starved people?

The elevated blood sugar lead to

- Increased insulin

- Decreased glucagon

= Stimulates glycogen, fat and protein synthesis

These processes require minerals such as phosphate and magnesium, as well as vitamins like thiamine

Insulin stimulates uptake of potassium into the cells, and phosphate and magnesium also enters the cells

= This rapidly decreases serum levels of these minerals

Hypophosphatemia

Hypokalemia

Hypomagnesaemia

- Predispose to potentially deadly effects like HF, arrhythmia, muscle spasm and coma

How to prevent refeeding syndrome?

Starved patients should start with a low level of energy replacement

- Vitamin supplementation should be given

- Electrolyte and fluid imbalances should be corrected during refeeding

In what conditions can the starvation be accelerated beyond the normal rate?

- Trauma

- Tumors

- Postoperative states

Can cause accelerated starvation because they both cause low food intake & high metabolic rate

Pregnancy - accelerated starvation?

Fetus functions as a parasite - takes everything it needs from the maternal circulation - even though mother is starving

IF mother is starving, will ketone bodies and hypoglycemia cause damage to foetal brain

Alcohol intoxication - accelerated starvation?

Patients affected usually vomit and are undernourished

- Alcohol inhibits gluconeogenesis -> which is essenital for maintenance of body functions during starvation