Nutrition / Energy Balance Flashcards
causes of malnutrition
- impaired access (poverty, immobility, disasters, famine, war; cultural / ethnic / traditional food preferences; poor dentition, eating disorders, anorexia)
- impaired ingestion, digestion, absorption
- impaired utilization
essential macronutrients
*glucose
*amino acids (10 essential amino acids)
*fatty acids (linoleic and linolenic acid)
sources of glucose
from sugars, starches, and complex carbs
sources of amino acids
*protein
*10 essential amino acids: cannot be synthesized by must; must be acquired from the diet
*non-essential amino acid nitrogen
sources of fatty acids
*from fats
*2 essential fatty acids: cannot be synthesized by body; must be acquired from diet:
-linoleic acid
-alpha-linolenic acid
caloric contents of carbohydrates
4 kcal/gram
caloric contents of protein
4 kcal/gram
caloric contents of fat
9 kcal/gram
caloric contents of alcohol
7 kcal/gram
storage of glucose
*liver glycogen
*muscle glycogen
storage of fat
*adipose tissue
storage of protein
*muscle protein
how are the macronutrients interconverted?
*all 3 macronutrients (glucose, amino acids, fatty acids) can be inter-converted by the LIVER
post-prandial energy flux
*after eating a meal
*“storage mode” or anabolic mode
*anything leftover is stored as glycogen, adipose tissue, and muscle protein
inter-prandial energy flux
- mobilization of glycogen stores to support metabolism
- minor release of fatty acids from adipose via lipolysis
energy flux during an overnight fast
- glycogen stores are gone
- mobilization of fatty acids and amino acids; gluconeogenesis in liver
energy balance =
*energy balance = caloric intake - total energy expenditure
*in disease states, we want energy balance to be NEUTRAL or POSITIVE (esp in acute illness)
total energy expenditure (TEE)
30%: activity energy expenditure (AEE)
+
10%: thermic effect of food (TEF)
+
60%: resting energy expenditure (REE)
resting energy expenditure
*the sum of basal metabolic energy expenditure and sedentary activities
*organ contribution to REE (LIVER 29%, brain 19%, muscle 18%, heart 10%, kidney 7%, fat < 1%)
*REE is proportional to Fat Free Mass (because fat is metabolically inert)
*REE is modified by many factors: age, gender, growth, hormones, smoking, disease, pregnancy
physiologic factors affecting resting energy expenditure
*increase REE: growth, pregnancy, lactation, lean body mass
*decrease REE: aging, fasting
pathological factors affecting resting energy expenditure
*increase REE: trauma/burns, inflammation, fever, sepsis, hyperthyroidism
*decrease REE: hypothermia, hypothyroidism
thermic effect of food
*energy cost of absorption, digestion, and transport
*dietary fat requires 60 cal to convert to body fat
*dietary glucose requires 140 cal to convert to liver glycogen
*dietary protein requires 480 cal to convert ot muscle protein
AVERAGE TEE of a mixed meal = 200 cal
measuring energy expenditure
*double labeled water
*direct calorimetry
*indirect calorimetry
rule of thumb estimation of total energy expenditure
*based on:
1) BMI
2) level of activity
average = 30 kcal/kg of energy expenditure
positive nitrogen balance
*requires sufficient intake of essential amino acids
AND
*requires sufficient TOTAL caloric intake (regardless of dietary protein intake)
*cannot be “forced” by intake of large amounts of protein or amino acids alone
negative nitrogen balance
*negative nitrogen balance in catabolic stress can be mitigated (“protein sparing”) by giving:
-enough glucose to turn off gluconeogenesis
-enough amino acids to spare muscle protein
clinical impact of protein/calorie malnutrition
*delayed post-surgical wound healing
*delayed recovery from severe trauma
*increased mortality in severe burns
*impaired immune response to infection
*increased toxicity of chemotherapy
*growth failure in pediatric patients
