Energy Flashcards
what is EAR?
estimated average requirement
-the average daily amount of nutrient to maintain body functions in half of a specific healthy population
what is RDA?
Recommended dietary allowances
- average daily amount of nutrient that is adequate to meet the nutrient requirements of almost all healthy people in a particular group
why is RDA set above EAR?
to prevent nutrient deficiencies
what is AI? How does it differ from RDA?
Adequate intakes
-the average daily amount of a nutrient that is estimated to be sufficient to maintain a specific criterion or normal bodily function
AI is used when there isn’t enough information for RDA- the approximation of needed nutrients when RDA doesn’t exist
what is UL?
tolerable upper intake levels
-maximum daily amount of a nutrient likely to pose no risk of adverse health effects for most of the healthy population
what DRI is used when RDA is unavailable?
AI is used as a goal for usual intake by an individual
what 3 things is energy needed for?
1) basal metabolism
- growth / maintenance
2) Thermic effect of food (TEF)
3) Physical activity (EEPA)
Where is ATP stored?
ATP is not stored, the balance between ADP/AMP is tightly regulated
how are the 2 sources of heat production classified?
1) obligatory ( essential)
2) regulatory
what are obligatory sources of heat production?
-anabolic and catabolic rxns
-fundamental molecular transport processes (absorption, digestion and storage of nutrients)
what are regulatory sources of heat production?
reactions involved in homeostasis of body T and maintenance
-shaking and uncoupling
what is the rate limiting step in oxidative phosphorylation?
the availability of ADP
what does uncoupling cause?
increased heat production as a result of increased O2, NADH and FADH consumption and decreased ATP production
what percentage of energy is lost as heat during energy conversions?
60%
what makes FA yield more energy as a macro?
the high number of carbon bonds
what are the major functions of GI tract?
Digestion and absorption
what is the purpose of propulsion, grinding and retropolsion?
aids in the breakdown of food in order to increase SA and gives enzymes contact to the food
why is the stomach so acidic?
in order to activate zymogens, denature proteins and kill bacteria
how long is the small intestine?
10 ft
what is the major role of the small intestine? how does its structure increase the ability to achieve this?
absorption
- vili and microvilli allow for increased SA which increases absorption
what part of the small intestine is attributed to majority of absorption?
the jejunum
- due to its high number of enterocytes
what is the life span of enterocytes? why is it this long?
72 hours
- they are very metabolically active which helps to facilitate minimization of toxicity
How are water soluble nutrients transported?
directly into capillaries in the liver
how are fat soluble nutrients transported?
via chylomicrons into lymphatics
-CMs are too large to enter blood capillaries
what are the 2 primary bile acids?
cholic acid and chenodeoxycholic acid
what are the 2 secondary bile acids?
deoxy cholate and lithocholate
what percentage of bile acids are lost a day?
1%
-very efficient, they metabolize 10-50g per day
what nutrients does the stomach absorb?
water, alcohol and some minerals
what nutrients does the small intestine absorb?
most vitamins and minerals to varying degrees in each part of the SI
what nutrients does the jejunum absorb?
lipids, monosaccharides, amino acids and small peptides
what nutrients does the ileum absorb?
bile salts and acids
what nutrients does the large intestine absorb?
water, electrolytes, vit K, biotin and SCFAs from bacteria
what is gastrin? where is it released from?
released from G cells, it increased HCL secretion, motility and pepsinogen release
what is secretin? where is it released from?
secreted by S cells, responds to increased acidity
-stimulates HCO3- release and enzymes
what is CCk? where is it released from?
secreted by I cells
-stimulates release of pancreatic enzymes and bile
what is somatostatin? where is it released from?
secreted from D cells
- inhibits HCL, motility, pancreatic and gall bladder secretions
what is BEE? how does it differ from RMR?
basal energy expenditure
- energy expended at complete rest
-RMR measures resting metabolic rate which is typically higher due to individual not being completely sedentary
what is TEF?
Thermic effect of food
- energy expenditure as a result of digestion, absorption and storage of food
What is EEPA?
energy expenditure from physical activity
- from physical movement or work whether planned or not
what can be considered adaptive thermogenesis?
cold adaptation, medications and emotion
what percent of total daily expenditure does BEE account for?
60%
what percent of total daily expenditure does TEF account for?
5 - 15%
what is NEAT and EAT?
NEAT - Non-excercise activity thermogenesis
-jittering, shopping, talking
EAT- exercise activity thermogenesis
how is energy expenditure directly measured? what are the pros and cons?
changes in body temperature are measured through heat production
pros: accurate
cons: difficult, expensive, impractical for day-to-day, short term measurements
how is energy expenditure typically indirectly measured? what are the pros and cons?
O2 consumption and CO2 production is used as a marker of heat production
pros: accurate for short term measurements, real time data
cons: px must wear lots of gear, not a long term measure
how is energy expenditure indirectly measured with doubly labelled water? what are the pros and cons?
estimates energy expenditure by tracking the elimination of deuterium (²H) and oxygen-18 (¹⁸O) - Deuterium is lost only as water, while oxygen-18 is lost both as water and carbon dioxide.
pros: free living, long term measurements, accurate, non-invasive
cons: expensive, estimation, doesn’t measure specific activity expenditures
what assumptions are made when measuring direct energy expenditure?
1) all energy is expended as heat
2) constant metabolic rate
3) all energy production occurs aerobically
4) energy consumed during measurement is expended and not stored or converted to another form of energy
what assumptions are made when indirectly measuring energy expenditure using RQ?
1) RQ is the ratio of CO2 produced to O2 consumed and reflects the macronutrient metabolized
what assumptions are made when indirectly measuring energy expenditure using doubly labeled water?
1) RQ is the ratio of CO2 produced to O2 consumed and reflects the macronutrient metabolized
2) rate of water turnover is constant throughout measurement period
3) isotope distribution through body is even
4) isotope loss through the body is only through water and not metabolic processes
how much energy is released from protein from the complete oxidation in a bomb calorimeter? what about in the body?
5.4 kcal/g in a bomb calorimeter
4 .2 kcal in the body
why is there such a big difference between energy expenditure of protein from bomb calorimetry to bodily metabolism?
in calorimetry proteins are more efficiently metabolized whereas in the body nitrogen is excreted in urea and does not account for energy expenditure
how much energy is released from carbs from the complete oxidation in a bomb calorimeter? what about in the body?
bomb cal - 4.1 kcal/g
body - 4.1 kcal /g
how much energy is released from fats from the complete oxidation in a bomb calorimeter? what about in the body?
bomb cal - 9.3
body - 9.3
how much energy is released from alcohol from the complete oxidation in a bomb calorimeter? what about in the body?
bomb cal - 7.1
body- 7.1
what is the RQ for carbs?
1.0
what is the RQ for protein?
0.80
what is the RQ for fats?
0.71
what is the RQ for alcohol?
0.62
what is the average RQ value for food metabolism?
0.82
in doubly labelled water, which isotope is only excreted through loss of water?
Deuterium (2H)
in doubly labelled water, which isotope is excreted through loss of water AND Co2?
Oxygen-18 (18O)
how many days of measurement are needed to account for a 3-4 moth block of time?
7 days
what form of energy expenditure has the least change from person to person?
TEF
- 1-2% changes
what type of energy expenditure has the greatest amount of change from person to person? why is this?
BEE (RMR)
- variance of >80% which is due to fat free mass
what could you expect a graph to look like after months of intervention on an extreme diet?
initial quick change followed by a plateau after the body has adapted to create a new baseline
how does higher amounts of lean body mass affect heat production?
leads to slightly higher heat production
why does prior food intake have a larger effect than food just eaten?
the body will turn over older food sources as opposed to using newly ingested sources
what percent of BEE is accounted for body size?
80%
what percent of BEE is accounted for TEF ?
5 - 15%
what is often an explanation for the variance in TEE for people who are the same size given the assumption that TEF has little variance among people and body size accounts for 80% of energy expenditure?
changes in EEPA
-mostly NEAT
what 2 factors account for variability in NEAT?
1) environmental
- egocentric (personal impact) and geocentric (environment)
2) Biological
what is a large factor of NEAT?
occupational activity level
what physical activity level (PAL) would be predicted for someone who is chair bound occupationally?
1.2
what physical activity level (PAL) would be predicted for someone who is does strenuous work occupationally?
2 -2.4
aside from occupation, what is another large environmental factor that has influenced energy expenditure?
increases in convenience
-dishwasher, washing machine, vehicles etc.
what 2 biological factors are involved in NEAT energy expenditure?
1) hypothalamus
- regulates / controls NEAT
2) Opioids
- controls neural control proteins that control wakefulness, arousal and NEAT
when the body is in a positive energy balance what happens to NEAT?
NEAT will increase
-the body predicts fat gain from a positive energy balance and will increase NEAT to decrease risk of fat gain
- opposite for negative balance
what is the estimated positive E balance?
1%
how is change in E body stores calculated?
EI - EE
metabolizable energy - heat
how long does it take for glycogen stores to deplete? what is used next as an energy source?
24 hours
- fat or protein used after longer fasting periods
what energy source does the body most readily store?
fat
- the body sees fat is very valuable so it is more likely to store it rather than break it down for energy
what does nutrient balance rely on the premise of in terms of CHO and protein conversion?
Nutrient balance is based on the premise that when energy is in balance CHO and protein are not converted to fat
when is nutrient and energy balance achived?
when intake = the body’s rate of oxidation of each macronutrient
what is the daily oxidation of carbs when nutrient balance is achieved?
71%
what is the daily oxidatioon percentage of stored energy for protein when nutrient balance is achieved?
2%
```
~~~
what is the daily oxidatioon percentage of stored energy for fat when nutrient balance is achieved?
<1 %
how does the changes in daily oxidation differ between macronutrients as a result of overfeeding?
carbs and protein are capable of faster changes in oxidation in comparison to fat which is not as readily oxidized
what is the hierarchy of oxidation? what is largely dependent in the hierachy adhering to this?
alcohol > protein > carbs > fat
-the amount of alcohol consumption; some people don’t drink alcohol so this would not be a factor in oxidation of macros
What is the heirarchy for oxidation of macros based on?
1) storage capacity
2) energy cost of conversion
3) specific fuel needs of tissues
How is fat oxidation calculated?
TEE - other oxidation (protein, CHO and alcohol)
where is alcohol and amino acids stored?
they are not stored
-toxic to the body
what percentage of lean muscle is comprised of protein?
~ 20%
what percentage of adispose tissue is comprised of fat?
~85%
what body system controls “set point”?
The CNS
what structure in the body is resposible for satiety?
Ventromedial hypothalamus
what structure in the body is resposible for hunger (feeding center)?
lateral hypothalamus
what do efferent signals regulate in regards to energy balance?
level of hunger / food-seeking, energy expendeture, energy partitioning, reproduction and growth
what do afferent signals regulate in regards to energy balance?
they control the energy balance through regulation of various signals
What kind of receptors does the gut respond to after eating a meal?
stretch receptors (mechanical) and peptides from GI tract (chemical)
what is the role of ghrelin? what type of neurons does it act on? and what does that stimulate?
Increase food intake by acting on orexigenic neurons in the hypothalamus to release NPY and agouti-related protein
where is ghrelin released from?
the stomach
where is cck released from? what stimulates this?
the intestine
-stimulated by AAs and FA
what do most GI tract peptides result in?
inhibition of eating
Where is leptin secreted from? what does it do?
secreted by adipocytes to reduce food intake and elevate EE
where is insulin secreted from? what does it do?
secreted by beta cells in the pancreas, it reflects fuel availibility
-higher insulin levels = reduction in appetite
what is insulin resistance?
a lack of sensitivity to insulin, more has to be secreted for the same effect
are meal derived signals short term or long term? what system are they collated by?
short term signal collated by the nucleus of the solitary tract (brain stem)
where are both short term and long term signals collated? where is this located?
the paraventricular nucleus (PVN)
-located in the ventrimedial hypothalamus (VMH)
what is the Arcuate Nucleus (Arc) in the hypothalamus responsible for?
converging adiposity signals (ie. insulin and leptin receptors)
what are the 2 adiposity signals?
Leptin and Insulin
what do some neurons in the Arc secrete when in negative E balance? what affect does this have on the body?
secrete NPY and agouti-related peptide which increases food intake
what is secreted by the Arc in order to reduce food intake? what pathway is this done by?
pro-opio-melanocortin (POMC) or cocaine-amphetamine related transcript (CART) which reduce food intake through the melanocorin pathway
when in a negative E balance (energy defecit) which system will be stimulated? which nerve is this done by and what is the result?
the parasympathetic nervous system through the vagus nerve
-results in an increase in energy storage
when the body has excess energy what system will be activated? what does this result in?
sympathetic nervous system and adrenal medulla is activated to promote energy expenditure
what 2 factors play a major role in obesity?
Genetics and Environment
what BMI level would classify someone as obese?
> 29.9
what BMI would classify someone as pre-obese?
25 - 29.9
what 3 classes of obese are categorized by BMI?
Class I: BMI 30 - 34.9
Class II: BMI 35 - 39.9
Class III: BMI > 40
how has the cost of obesity changed over the years? what are the two classifications of obesity costs and which one plays a larger role?
the cost associated with obesity has seen a gradual increase over the years
-indirect costs typically play a larger role
how does BMI play a role in risk of mortality?
BMI > 25 will exponentially increase mortality risks
what are other common health risks associated with obesity?
diabetes, dyslipidemia, high blood pressure and metabolic syndrome
what is metabolic syndrome? what are some factors to determine this?
Insulin resistance syndrome
-describes individuals who are more than just obese and have increased risk of CVD and diabetes
Waist circumfraence, BMI, TAG level, [HDL], blood pressure, glucose level
why is BMI not always a good marker of obesity? what can be used instead?
BMI is not a diagnostic, it doesn’t account for fat vs fat free mass
1) waist to hip ratio / circumference
2) body composition
name some factors associated with weight maintenance vs regain following intetional weight loss?
what are treatments for obesity?
1) increased PAL / lifestyle changes
2) weight loss - 10% loss can improve risk factors
3) Prevention- control / regulation of energy intake
4) surgery
5) anti-obesity drugs
- stimulants to increase EE or satiety
