Week 6 readings summary Flashcards
what is TEE?
total energy expenditure
represents the summed daily metabolic activity of all organ systems
what is the most variable component of TEE?
PA
what is additive TEE?
Energy spent each day on non-PA physiological activity is fixed and doesn’t change, regardless of variation of PA
what is constrained TEE?
non PA EE adapts dynamically to variation in PA to maintain TEE within some narrow physiological range
what happens in the additive TEE model?
EE increases with PA in a linear dose-dependent manner. Non-PA metabolic activity (which includes basal metabolic rate) is not affected by variation in PA.
what happens in the constrained TEE model?
TEE is homeostatically maintained within a narrow range. Increasing PA has a limited effect on TEE and instead leads to a reduction in non-PA metabolic activity to keep TEE near its set point
How does natural selection favour constrained TEE?
For organisms with high PA during food-poor periods, an additive TEE strategy would maximize energy requirements precisely when the risk of starvation was most severe, whereas a constrained TEE strategy would reduce energy requirements and mortality risk
For organisms that work hardest when stockpiling food energy during food-rich periods, a Constrained TEE strategy would lower energy requirements and thereby maximize surplus energy gain.
A Constrained TEE also could reduce the risk of predation while foraging by reducing the amount of time needed to obtain food during high-PA periods.
what is the evolutionary cost of a constrained TEE strategy?
the reduction in energy allocation to non-PA activity, particularly reproduction, during high PA periods
why is a constrained TEE strategy beneficial?
A Constrained TEE strategy keeps energy requirements in check while allowing the organism to prioritize and allocate energy among various organ systems in a dynamic manner that is responsive to current conditions and maximizes lifetime reproductive fitness.
disadvantage of additive TEE model
an animal will lose somatic capital (body weight) rather than increasing EE in high PA conditions to compensate for the high PA
Conclusions of PA, TEE and body size?
In populations where PA and food availability are both high, developing individuals may target a higher TEE and smaller body size, reducing non-PA metabolic requirements while maintaining a higher TEE ceiling
when do effects of increased PA diminish?
as the body adapts to higher levels of PA to maintain TEE
static approach of energy balance
This approach states that a ‘change in energy stores = energy intake − energy expenditure’ and assumes that by simply changing either side of the energy balance equation weight is gained or lost.
disadvantages of static approach of energy balance model?
doesn’t consider individual differences
doesn’t take into account increase in EE that would occur as body weight is gained
what is a dynamic process of energy balance?
This means that altering one component of the energy balance equation (i.e., reducing energy intake or increasing energy expenditure) can affect numerous biological and behavioural factors on both sides of the equation in unpredictable and unintended ways
what factors regulating and influence energy balance?
genetics environment psychological metabolic energy intake/expenditure
effect of health related fitness on metabolic rate
The amount of PA needed to change fitness level depends on the overall energy cost of PA and the type, frequency, duration and intensity of the activity relative to body weigh
High fitness levels = high RMR
Thus, as health-related fitness increases the body becomes better at utilizing fat as a fuel compared to a sedentary individual at the same intensity of PA or exercise
effect of PA on muscle and bone
If muscle mass is lost, strength and RMR will decrease, resulting in an overall reduction in total energy expenditure
Muscle mass is gained or maintained through PA and helps prevent the typical decline in RMR seen during periods of energy restriction (e.g., dieting) because muscle mass is more metabolically active than fat mass
what happens when energy restriction alone is used to produce weight loss?
muscle tissue is lost
when body weight is lose due to energy restriction alone, what happens to RMR?
RMR declines, causing total daily energy expenditure to drop below predicted levels based on weight loss alone
when body weight is gained what happens to energy efficiency?
decreases because movement can be difficult and requires more energy
what has a recent review of studies found evaluating exercise and weight loss in dieters?
only lost 1/3rd as much weight as expected due to compensatory behaviours e.g. increased hunger due to exercise
More common in women
what does higher-intensity exercise do?
suppress hunger or food intake during post exercise period
what activities suppress appetite?
running
skipping
high exercise interval
what stimulates appetite?
swimming
walking
How does the environment affect hunger?
Cold promotes
Heat blunts
what is energy flux?
energy flux refers to the rate of energy conversion for either energy expenditure or transformation to storage - , energy flux represents the amount of energy moving through the body each day
what does high flux do?
Maintains overall higher EE
Heightened sensitivity to appetite control
Allows for more appropriate energy intake or volume of food consumed
