Editing Acute malnutrition


== '''Metabolic response to starvation:''' ==

* After 12 hours
** Insulin levels fall and glucagon rises
** Liver glycogen converted to glucose
** Muscle glycogen broken down into lactate, which is converted to glucose in the liver
* After 24 hours
** De novo glucose production from non-carbohydrate precursors, predominately in the liver (breakdown of amino acids as a result of catabolism of skeletal muscle, up to 75g per day)
** '''Protein catabolism is readily reversed with administration of glucose'''
* More prolonged fasting
** Reliance on fat oxidation to meet energy requirements (glycerol converted to glucose)
** Hepatic production of ketones from fatty acids, which is facilitated by low insulin levels
** After 48-72 hours, CNS may adapt to using ketone bodies as primary fuel source (keto-adaptation). This does not occur in sepsis and trauma, so protein is catabolised to provide gluconeogenic precursors.
** Once the body switches to using 'fat economy', the protein catabolism is reduced significantly
** Resting energy expenditure will also decrease, maybe mediated by a decline in conversion of T4 to T3
** Reduction in resting energy expenditure from about 25-30kcal/kg/day to 15-20kcal/kg/day

== '''Metabolic response to trauma/sepsis/surgery:''' ==

* Development of a hypermetabolic state and increased protein breakdown
* Increased counter-regulatory hormones (adrenaline, norad, cortisol, glucagon, growth hormone)
** Within a few minutes of beginning an operation, these hormones start rising
* Increased energy requirement
* Increased nitrogen requirement
* Insulin resistance and glucose tolerance
* Preferential oxidation of lipids
* Increased gluconeogenesis and protein catabolism
* Loss of adaptive ketogenesis
** Contrast this with simple starvation
* Fluid retention with associated hypoalbuminaemia
* No evidence that provision of high-energy intake would actually be helpful in this setting

[[Category:Nutrition]]