Eating disorders

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Biochemistry

Basics

Mechanisms of eating behaviour

Homeostatic (set-point) mechanism

  • Assume that our bodies sense a set-point, which is defended through neurological and biochemical mechanisms
  • e.g.,
    • low glucose causes hunger
    • high glucose causes satiety
  • One obvious problem with this theory is that it doesn't seem to account for population-wide gorging (a la americans)
  • This system works best in older models in which food is not plentiful

Non-homeostatic (behavioural) mechanism

  • Has (as predicted by the name) a behavioural slant
  • Basically supposes that there are conditioned and unconditioned responses, and that we associate the two (e.g., hunger and eating) through behavioural conditioning
  • think Skinner..
  • An advantage of this model is that it is better equipped to address various eating disorders (e.g., overeating) in society today

Role of the hypothalamus

  • The hypothalamus' role is directly tied to its involvement in leptin
  • Plays a critical role in maintaining energy homeostasis by integrating and coordinating metabolic, neuroendocrine, and behavioural responses and arousal states.

Energy stores in the body

Carbohydrates

  • In the short term, carbohydrates are the principal energy source
  • Contains 4kcal/gram of energy (dry)
  • Stored in glycogen in the liver and muscle

Fat

  • In the long term, fat is the principal energy source
  • Contains 9kcal/gram of energy
  • Stored in adipose tissue

Proteins

  • Last resort energy source
  • Contains 4kcal/gram of energy (dry)
  • Proteins always account for some circulating glucose.
  • Proteins as sole energy source cannot continue for any length of time as it is incompatible with life.

Nutritional assessment

There are three important areas to analyze for a proper nutritional assessment:

  1. Food quantity and quality
  2. Intestinal absorption is intact (not diseased or damaged)
  3. Body metabolism is unimpaired

Starvation and malnutrition crisis

  • Several metabolic changes in starvation result in malnutrition crisis:
  1. Inability to gain weight due to net caloric deficit
  2. micronutrient or trace mineral deficiencies due to lack of variety of food.