Energy Balance Flashcards
Describe the thermodynamic principles of energy balance:
- 1st law = energy can be transferred from one system to another but cannot be created or destroyed
- Thermodynamics apply to the human body
- EI = EE = +/- energy stored(pro, CHO& fat)
How can Energy intake be measured?
- weighed food recordings
- Food frequency questionnaire
- 24-hr recall
What are the 3 factors which make up EE?
RMR - energy needed for basic physiological functions e.g.: breathing, circulation& maintaining body temperature 60-80% of TEE
DIT - increase in energy expenditure above the basal fasting level after food consumption. It contributes to 10-15% TEE
PAEE - enery expenditure from all skeletal muscle contraction 20-25% of TEE (made up of NEAT & Exercise)
Explain the set point theory:
- Biased system - body does not like restricted energy intake, causing us to eat more and crave more food, metabolic rate decreases with low energy intake
- Upper and lower boundaries of physiological regulation, with passive control in-between
- Weak upper boundary
- People tend to gravitate to their natural setpoint
- Leptin tells the brain the amount of energy stored in adipose tissue. Regulates changes in fat mass, by exciting/inhibiting arcuate nucleus in hypothalamus regulates food intake and reduces metabolic response to increase leptin & food intake
- Individuals with less ability to put on weight have narrower zones, so their body initiates responses more sensitively
how many KJ are in:
- CHO
- Fat
- Protein
per L of O2
- CHO: 20.8KJ per L O2
- Fat: 19.6KJ per LO2
- Protein: 19.4KJ per L02
What is an energy flux?
Energy flux
Healthier is the PA person, as energy comes into the body and is expended quickly
- Stagnant of lipids in muscle is linked to type 2 diabetes in obesity as stored as ectopic fat
- Low energy flux = low EI & low EE
What is the oxidative priority of these substrates?
- protein
- fat
- Alcohol
- CHO
Alcohol –> Protein –> CHO –> Fat
fat stores are unlimited, compared to alcohol which is a toxin so is not stored at all
How is indirect calorimetry measured?
double-labelled water technique:
- people ingest isotopes of hydrogen & O2.
- Blood, urine & saliva measured for: CO2 production to O2 consumption when food is combusted
What are the metabolic adaptations associated to energy balance/protecting against neg EB?
Increasing perceptions of hunger
* Hormones
* Reward
* Resting energy expenditure
* Exercise energy expenditure
How does the brain react to increased a negative energy balance?
- increased ghrelin, decreased GLP-1, PYY, CKK (increase hunger)
- decreased leptin(decrease EE)
calculation for kcal per mile:
- walking
- running
- o.36(weight in lbs) for walking
- 0.69(weight in lbs) for running
What is meant by a dynamic equilibrium?
Idea of slow dynamic response, when restricting energy intake will cause the person to find an energy balance at a lower level of energy intake
how does energy expenditure change over a person’s life course?
- Subjects aged 8 days to 90 years
- Described total energy expenditure (absolute) & energy expenditure adjusted for fat-free mass and fat mass
DLW(doubly labeled water) allows experimenters to see an accurate measurement of free living o2 expenditure - At 60 yrs is when the total daily energy expenditure decreases causing weight gain
- BMR is very closely related to the amount of non-fat tissue in the body, the fat-free mass (FFM) or lean body mass. The larger someone’s FFM, the larger (in general) their BMR - BMR is regulated by the thyroid hormone
How can mechanical efficiency influence EE?
- The EE per mile is not influenced by speed when running
- Walking speed influences the EE per mile - because the mechanics are less efficient
- Swimming speed drastically influences the EE per mile
Walking kcal / mile = 0.36 x weight (lbs)
Running kcal/mile = 0.69 x weight (lbs)
- During a 30 min walk (3 mph) a 91 kg person expends 159 kcal
30 min jog (4 mph) = 210 kcal
71 min jogging to expend 500 kcal
Why does EE reduce with weight loss?
- mechanically more effective
- moving a lighter mass
Substrates that contribute to metabolism during exercise:
M-GLY = muscle glycogen
GLU - glucose
IMTG - intramuscular triglycerides
NEFA - Non-esterified fatty acids
fats at lower intensity, M-GLY in high intensity
How does exercise impact appetite short-long term?
- Single bout transiently suppress appetite & delays eating (reduced ghrelin, increased PYY and GLP-1
- Over several days, compensation for the EE of exercise by increasing EI by 1/3
- Over a longer period, EB will be re-established
What is NEAT?
What are its short-term effects on exercise
- Non-exercise activity thermogenesis
- NEAT is energy expenditure of all PA other than voluntary exercise
- measured by accelerometers/ from measures of TDEE
- In young and healthy individuals, single bouts of exercise does not influence NEAT or seem to induce a compensatory decline in NEAT.
- High volumes of exercise training may stimulate a compensatory decline in NEAT in older adults
- NEAT can be increased through fidgeting, weight gain mainly for those with high sedentary time
Describe EPOC:
Explain DIT:
Post-exercise energy expenditure(EPOC):
- post-exercise increase in metabolic rate
* Not affected by exercise as EE did not increase sig after exercise
- The increase in energy expenditure above basal fasting level directly related to food ingestion –> intestinal absorption & initial metabolism & storage of nutrients
- DIT represents about 10% of the total amount of energy ingested over 24 h
- 0-3% for fat, 5-10% for carbohydrate, 20-30% for protein, and 10-30% for alcohol
—> fat is broken down very efficiently - not affected by exercise
What is the association between exercise and weight loss?
Being active & resistance training reduces the amount of lean mass that is lost during weight loss interventions. This is because restricted EI can lead to lean mass loss as well as adipose tissue
- Especially important to diabetics
What are 2 metabolic strategies of TEE?
- Additive TEE - increasing EE without it impacting RMR
○ Increases in PA, increases TEE leading to a negative energy balance - Constrained TEE - increased TDEE plateaus off because is associated with a lower RMR
- Increased TDEE decreases reproductive activity, growth & repair of cells
- Plataeus off to keep TEE & RMR in a dynamic narrow range
○ Reduces energy requirements and mortality risk for individuals in an energy surplus
Both cases long-term mean TEE is equal to mean food energy intake
