Metabolism and nutrition

From Iusmphysiology

  • started here on 02/25/11 at 11AM.

Contents

[edit] Metabolism and Nutrition

[edit] Metabolism

  • In a young, healthy person, you need 30 kcal per kg of body mass.
  • The BMR is measured under standardizied conditions; this is a clinical definition of resting medabilic rate.
    • A little higher for males than for females.

[edit] Energy balance

  • First law of thermodyn:
    • Energy neighter created or destroyed
    • So we take in energy (diet: carbs, fats, prots, vitameins, etc.)
    • And it must equal energy output (detox, movement, etc) + energy we store
    • POstive energy balance = put on weight.
    • Negative energy...
  • Second law:
    • Chemical transformations always result in a loss of free energy
    • E = gibbs free energy +
    • As you eat glucose, you have an increase in your internal energy.
    • T*delta-S can never be zero, so if we add no E to the system, deltaG must decline.
    • So if we burn a mole of glucose
    • So we burn some and we store some
    • Storage goes into high energy phosphate bonds.

[edit] Glucose metabolism

  • Body stores energy as glycogen and TAGs
  • Carbs = 4.1 kcal / g
    • Body has 120 g of glycogen in liver, and 600 g in muscle
    • ABout 3000 kcal which is over your BMR so you can live on your storage for 1.5 days.
  • Lipids = 9.4 kcal / g
    • Body has 14 kg of fat = 130K kcal!
    • Can live on his fat for about 63 days.
  • Protein = 4.3 kcal / g
    • Serves structural and functional role
    • 14% protein = 20K kcal in protein but only half can be mobilized as energy b/c the other half has impt function
    • Less than 5% of protein catabolism is used for BMR.

[edit] Interconversions

  • We can convert between carbs and lipids (lipiogenesis), etc.
  • AA can be converted to TAGS or glycogen
  • Lipid can only be stored, though, not converted.

[edit] Energy liberation

  • Muscle and liver:
    • Epi binds, activates adenylate cyclase, PKA activated, Glycogen phosphorylase activated to break down glycogen.
    • Glucagon has same effect
  • Adipocytes
    • Leads to activate ion of lipase to release Fatty acids

[edit] Nutrition

  • Water, vitamins, minerals are important to maintain function (hence we can't live wihtout food for 63 days).
  • Requirements:
    • Carbs: none, shouldn't differ with activity, age, etc. though.
      • Typically 55-60%
  • Lipids: will differ by individual
    • about 25-30% is appropriate, 60% is typical.
  • Activity level is impt determinant of changes in caloric intake.


[edit] Atkin's diet

  • Not true that wasting occurs
  • What really happens is that carbs are low, ketone bodies are high, and glucogenogensis is on b/c glycogen is being broken down.
  • In diabetes, ketones are so high you can smell the fruity breath.


[edit] CArbs and fats

  • Need palmitic acid, oleic acid in order to make linoleate and linolate.
  • Make arachidonic acid (for lots of other things)
  • Get these from fish
  • Lipoprotein lipase can easily break fats of cis monounsaturated but not trans.
    • So trans stays around longer and causes problems; increases LDL levesl and decreases HDL levels.

[edit] Proteins

  • 9 essential aas
  • Vegetarians at risk for not getting essential aas.
  • Use a scoring system to judge how well a food provides these essential aas:
    • Egg is the standard at 100
    • Each food is scored by it's lowest scoring essential aa relative to the 100 of the egg.
  • There is a second scoring system from the WHO
    • BAsed on aa requirements of humans
    • Score of 1 means it meets all the aa needs of the human.
    • Eggs and beans are 1
  • Other systems, too:
    • Biological value (BV) looks at how much of the material is actually retained in the body
    • Efficiency ratio (PER) looks at how well the material is converted to body mass
    • Net protein utilization (NPU) looks at how much of the protein is reatined....?


  • Need about 0.6g of protein / kg / day
  • Recommended at 1.0g for kids and 2.0 g for first 6 months
    • For establishing growing body
  • Higher requirements for:
    • Athletes
    • Pregos
    • Burn victims
    • Aids pts (muscle wasting)

[edit] Vitamins and minerals

  • Not going to be tested.
  • Chromium has a unique way in lowering chol.
  • Cr in drinking water inhibitns insulin resistance.
  • May be that increase in chol causes an initial impairment of glucose movement.
    • Can initially be fixed with cr.
    • Then later cannot be fixed with cr.

[edit] Regulation of food intake

  • Hypothalamus controls sensation of hunger.
  • Anorexics inhibit feeding:
    • CRH corticotropic releasing hormone
    • alpha-melanocyte stimulating hormone
    • Cocaine
    • GLP1
  • Orexigenics increase feeding:
    • NPY stimulates feeding
    • NE
    • couple others

[edit] Loops

  • Short term regulation:
    • GI hormones affect short term regulation; think CCK
    • Insulin released after a meal, decreases feeding
    • Glucose after a meal is high, decreases feeding
    • Glucose is low before a meal, increases feeding
    • CCK works at the ventral medial nucleus
  • Long term
    • Leptin released from fat, inhibits feeding center and stimulates the satiety center.
    • Leptin levels correlate well with adiposity.
    • OBOB mice are HUGE and have high levels of leptin and mutated leptin receptors.
  • Majority of obese have high leptin levels which means they are partially resistant

[edit] Obesity

  • Obesity is a chronic excess of caloric intake.
  • 1 kg of fat is 9400 kcal
  • Adipocytes can hyperplasia and hypertrophy
    • Plastic increases only in the first few years of life
      • Means later in life more adipocytes can hyperplasia
    • HYperplasia is how older peep get bigger
  • Skinny kids less likely to become obese because fewer cells to hypertrophy
  • Fat goes to skeletal muscle and liver when adipocytes cannot hyperotrophy any more.
    • Causes lots of metabolic problems.

[edit] Starvation

  • Conscientious objectors starved themselves.
  • Univ. of Minn wanted to work on starvation
    • So instead of war, people volunteered for starvation study.
  • Starvation is a depletion of carbs
  • Ulstimately you die for lack of minerals and vitamins.
  • First thing to happen is depression and hysterics.
  • Slowly took away food over 12 weeks.
  • One pt chopped off all of his fingers.
    • Didn't know if he wanted to or if it was an accident.
  • So, eat.


  • stopped here on 02/25/11 at 12PM.
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