Substrate Metabolism and Energy Balance - Is a Calorie really a Calorie Flashcards
state the 3 components of energy expenditure (EE), and the relative percentages of EE that they take up
1) PAEE: 10-15%
2) DIT: 10%
3) RMR: 65-75%
can we store more fat or carbs in the human body?
the human body can store far more fats than it can carbs
state 2 facts about fat storage in the human body
1) 4.4g circulating the blood, 1200g stored in adipocytes, and 300g stored in muscles
2) fat stores equate to over 100,000 calories - enough energy to survive off for days and days
how much carbohydrates are stored in the body?
1) 5g circulating the blood, 350-700g stored in the muscles, and 100g stored in the liver
2) carb stores add upto less that 3200 calories (a real small amount compared to fat stores)
what does carb storage in the muscles depend upon?
depends on dreary intake, and endurance training status - more endurance training, for the same amount of carbs in the diet, you will store more muscle glycogen
do liver stores seem to be affected by endurance training status too ?
no, the liver doesn’t seem to be affected by endurance training status like the muscles do
state 1 fact about an obese person’s ability to store fat
someone who is classified as obese has a much higher capacity to store fats than other individuals
what is leptin ? (2 points)
1) a hormone secreted by the adipocytes which surpasses appetite
2) helps control BW in a negative feedback loop - more adipocytes = more leptin, less adipocytes = less leptin
state 2 facts about people with leptin deficiency
- completely lack the production of leptin, meaning their appetite is huge
- 98% of people are not affected by this
what gene is linked to leptin deficiency ?
the FTO gene - it works by appetite
what do we know about the FTO gene ?
we know that the FTO gene works by appetite. people who have this gene have a much larger appetite than those who don’t, and struggle enormously with weight control
explain the study design by (Stubbs et al., 2014) about how measuring energy intake is not easy
- got volunteers who agrees to be locked in a room for a couple of days and studied them under different conditions
- under some conditions, the participants were told the they were being observed, under others occasions they tried to blind that from them
what does the blue bar represent in the results figure published by (Stubbs et al., 2014) in his study on measuring food consumption?
represents the actual amounts that were eaten as determined by the researcher who was giving them food (AKA - most accurate).
done covertly, participants unaware that they were being observed
what does the red bar represent in the results figure published by (Stubbs et al., 2014) in his study on measuring food consumption?
shows overt one where researchers still weighed the food, but participants changed their behaviour and started to eat approx. 5% less calories on average
what does the green bar represent in the results figure published by (Stubbs et al., 2014) in his study on measuring food consumption?
shows when the participants weighed their own food, they reported 10% less than the most accurate value
what does the purple bar represent in the results figure published by (Stubbs et al., 2014) in his study on measuring food consumption?
shows if you recall participants what they ate the day prior, it leads to about 15% less calories being recalled
what does the orange bar represent in the results figure published by (Stubbs et al., 2014) in his study on measuring food consumption?
shows the use of a food frequency questionnaire (FFQ) and is about 20% different to from the true values
what is the issue with overt measures ?
when you do an overt measurement, you get an observation bias - the participants change their behaviour
what is the take home message from (Stubbs et al., 2014) ?
the method you use to track energy consumption is very important due to the inaccuracies of some methods used
explain a study done by (Shai et al., 2008) on changing body composition (4 points)
1) low fat vs low carb diet
2) 24hr recall to estimate EE
3) both groups reported 1000 kcal deficit (and a year later)
4) FFQ showed 600 kcal, and 200 kcal 6 months later
explain the results found by (Shai et al., 2008) on changing body composition (4 points)
- if data true, should equal 30kg weight loss, but was only 0.7kg in low-fat diet group
- re-analysed data and found deficits get smaller over time
- if believed self-reported data, we should start to worry whether a calorie is a calorie
- issue was with the method of measurement, and not in the underlying physiology
what are the calories found in 1 gram of the following:
1) carbohydrates
2) proteins
3) fats
4) ethanol
1) carbohydrates = 4 kcal/gram
2) proteins = 4 kcal/gram
3) fats = 9 kcal/gram
4) ethanol = 7 kcal/gram
explain a study design done by (Stubbs et al., 1995) at Cambridge university
- locked students in a room
- put on wither low, mod, or high fat diets
- measured EI and EE
- measured the carb and fat balance of both the groups too (diff between amount of nutrient ingested vs amount of nutrient expended)
what were the results from the study done by (Stubbs et al., 1995) at Cambridge university
- not a large diff in fat carb balance, but large diff in fat
- one reason = when we manipulate carb content of a diet, our metabolism also alters (more carbs = more burning of carbs)
explain a study done by (Astbury., et al 2010) on a ‘pre-load’ technique
- the types of calories we eat affect both our appetite and our metabolism
- study gave participant a protein shake an hour before lunch as a ‘pre-load’
- measured how many calories were ingested at lunch
explain the results found in the study done by (Astbury., et al 2010) on a ‘pre-load’ technique
- as they inc^ protein content in the pre-load, the total calories ingested at lunch decreased
- higher protein intake seems to be liked with lower appetite and lower energy intake
state what it is meant by the key term - ‘direct calorimetry’
measures the heat production of an individual, in calories, when placed in an insulated chamber where the heat is transferred to surrounding water
state 2 issues with direct calorimetry
- inability to measure rapid changes in metabolism
- friction developed by ergometer would contribute to total heat produced during exercise
- not all heat produced during exercise would be immediately liberated from the body
- cannot determine which fuel source is being utilised at one time - only measures metabolic rate
state what it is meant by the key term - ‘indirect calorimetry’
calculates the heat that living organisms produce by measuring either their production of carbon dioxide and nitrogen wastes or from their consumption of oxygen
state 2 minor issues with indirect calorimetry
- expensive
- inconvenient for the athlete
- alters behaviour
- cannot be worn for extended periods
sate, and explain, 3 major issues with indirect calorimetry
1) intensity - intense exercise produces acidosis - our bicarbonate system buffers that - gives off more CO2 as a result - excess CO2 was not from our metabolism
2) conversion/production/oxidation of other substrates (e.g. - gluconeogenesis RQ = 0.13)
3) duration of exercise (steady state) - require at least 3 mins of exercise to get an accurate measure of substrate metabolism
what piece of equipment can be used for indirect calorimetry
‘Douglas bag’
state what it is meant by the key term - ‘Douglas bag’
an inflatable bag used to collect expired air for the determination of oxygen consumption and basal metabolic rate (BMR)
state what it is meant by the key term - ‘Double Labelled Water’ (DLW)
can be used as a method to measure the average daily metabolic rate of an organism over a period
what is the average error of DLW relative to direct calorimetry
DLW has an average 1-5% error relative to direct calorimetry
state how DLW is carried out (4 points)
1) based upon the use of stable isotopes of Hydrogen (H) and Oxygen (O)
2) when Deuterium (2H) and 18 O are introduced into the body, they mix in with the normal H and O
3) the 18 O is lost more rapidly than the 2H as is lost in both CO2 and H2O whereas the 2H is only lost in H2O
4) the difference in those rates is used to calculate CO2 production
state 2 disadvantages over the use of DLW
- high cost of equipment and very specialised staff are required to perform the analysis
- assumed the RER/RQ
- no info on the components of EE
- DLW provides no info on the pattern or intensity of PA
- only get an average EE over the period - cannot understand daily fluctuations
state 4 facts about - ‘activity diaries and recall questionnaires’
- mostly self-reported but can also be experimenter administrated
- usually utilise 10-15 min recording periods throughout the day
- many different recall questions
- used either an activity core of a MET value for recorded activity to estimate EE
who came up with the - ‘Compendium of Physical Activity’
(Ainsworth et al., 1993; 2000; 2011)
what is the ‘Compendium of PA’ (Ainsworth et al., 1993; 2000; 2011)
- compromised from a variety of published and un-published sources
- element of subjectivity required in both internal record of activity by the participant and the condor
- uses average of values for various activities
how does the ‘Compendium of PA work’ ?
1) 1 MET = BMR
2) therefore, the multiplication of a MET by the time will estimate EE
3) e.g. - 1.5 kcal/min (BMR) x 3 MET’s = 3.5 kcal/min/ ANS x 15 mins = 67.5 calories burnt
state 1 benefit and 1 drawback over the use of ‘pedometers’ and ‘accelerometers’
- both very good at predicting EE during ambulatory activities (e.g. - running and walking)
- doesn’t pick up data from non-ambulatory activities (e.g. - cycling)
state 1 benefit and 1 drawback over the use of ‘HR monitors’
- aim to pick up on info accelerometers miss - estimate EE on linear relationship between HR and EE (however, linearity is lost at low intensities)
- HR monitors require individual calibration and other factors can influence their results (e.g. - stress)
state what it is meant by the key term - ‘actiheart’
tech uses a combination of HR and accelerometry data . as sources of error are different for the two methods, it should theoretically become more precise
state what it is meant by the key term - ‘sensewear armbands’
worn on the upper arm; has measures of heat flux, bi-axial accelerometer, skin temp, and much more. the calculation for measuring EE is proprietary
