Energy Flashcards
What can energy balance effect?
Aesthetics
Health
Performance
What medical condition occurs with sustained chronic positive energy balance?
Obesity
What medical condition occurs with sustained chronic negative energy balance?
Anorexia
The principles of energy balance
The 1st law of thermodynamics
Chemical energy intake (food and drink) must equal the output of heat, mechanical work and chemical energy used in biosynthesis reactions
What is the 1st law of thermodynamics?
Energy can be transferred from one system to another but cannot be created or destroyed
How to calculate energy intake?
energy expended (heat, work (movement and metabolism) +/- energy stored (TAG, glycogen and protein)
How are humans evolved in terms of energy balance?
Humans have evolved to defend against negative energy balance
Negative energy balance is more resisted than positive energy balance
Genes are selected that favour energy accumulation and conservation
How many calories are in protein?
4kcal/g
How many calories are in fat?
9kcal/g
How many calories are in carbohydrates?
4kcal/g
How many calories are in alcohol?
7kcal/g
What determines energy input?
Behaviour
What determines energy output?
Thermic effect of feeding
Physical activity
Resting metabolic rate
What % of energy output is determined by the thermic effect of feeding?
5-15%
What % of energy output is determined by physical activity?
20-35%
Highly variable
What % of energy output is determined by metabolic rate?
60-70%
How is weight change determined?
Total energy intake - total energy expenditure
Theoretical options to understand how genes and are environments combine to regulate body adiposity? (Speakman et al. 2011)
6.7kg weight increase over 10yrs Thermo analogy - the deviation in body weight elicits reactions that work to bring back energy balance to its set point Adipose tissue (leptin) as a critical regulator
What is the role of leptin?
Leptin is produced in proportion to the amount of adipose tissue
It circulates in the body, which is monitored by the brain
The set-point model - theoretical strengths and weaknesses? (Speakman et al. 2011)
Strengths
- favoured by biologists/physiologists
- supported by calculations revealing precise EI-EE matching
- supported by robust adaptive responses to imbalance
Weaknesses
- can’t explain the current obesity crisis
- can’t explain why obesity differs by education and social status
- little focus on social, environmental and psychological factors affecting energy balance
Dual intervention point model? (Speakmen et al. 2011)
Upper and lower boundaries of physiological regulation
Passive control in-between influence by environment and psychology
Boundaries imposed by starvation and predation pressures
Genetic influences after the zone of passive control where there is no regulation to prevent change
Weak upper boundary
Constrained model of TDEE? (Pontzer 2015)
Total daily energy expenditure as a ‘constrained model’ rather than ‘additive’
Energy requirement kept in check by prioritisation of resources across physiological function
- reproduction
- immunity
- growth
- repair
Neuro-hormonal appetite control systems? (Field et al. 2008)
There’s a hormonal and endocrine system in place to help regulate food intake on an acute and chronic basis
Cross talk between peripheral tissue and the brain (hypothalamus and arcuate nucleus)
Tonic (chronic) signals - leptin, insulin
Episodic signals - coordinate food intake on an acute basis (PYY, GLP-1, CCK, ghrelin)
Circulation in the blood
Vagus nerve - gut to brain stem
What is the role of ghrelin?
The hormone that rises before meals and stimulates meal initiation and promotes food intake
What is the role of PYY, GLP-1 and CCK?
These hormones rise after meals and promote satiation and satiety
What is the episodic regulation of food intake?
Coordination of food intake on a meal-to-meal basis
Eating is metabolically stressful for the body
Hunger -> satiation -> satiety
Define satiation?
The process that occurs to bring a meal to an end
Define satiety?
The feeling of fullness between meals, that delay the choice to voluntarily eat
Pre-prandial metabolism - How are meals anticipated? (Begg & Woods 2013)
Parasympathetic signalling
Smell and sight of food
Time of day
Environmental cues
Pre-prandial metabolism - Effect on circulating levels of insulin, ghrelin and GLP-1? (Begg & Woods 2013)
Circulating levels of these hormones change dramatically leading up to a meal in order to prepare the body to receive food in order to buffer some of the metabolic stress associated with eating
Insulin increases -> buffer the increase in glucose from food
GLP-1 increases before insulin -> facilitate insulin productions from the pancreas
Circulating ghrelin increases
- hunger-stimulating hormone
- correlates with meal initiation
- increases the secretion of gastric juices and gut motility
What is meal quality linked to? (Blundell et al. 2010)
Sensory and cognitive satiety
- expectations
- rewards/pleasure
- recognition
- association
What is meal quantity linked to? (Blundell et al. 2010)
Early post-ingestion satiety
- stretching of the stomach
- osmotic lead
- increasing levels of CCK, GLP-1 and PYY
- decreasing levels of ghrelin
What is nutritional status linked to? (Blundell et al. 2010)
Post-absorptive satiety
- increasing in circulating ghrelin, glucose and amino acids
- oxidation
Define leptin and it’s effect on appetite? (Rosenbaum & Leibel 2014)
Released from adipocytes in proportion to adiposity Increases energy expenditure Mediator of the acute acting appetite hormone Starvation signal - immune function - reproduction function - thyroid function Disproportional changes Leptin resistance in obesity
What are the leptin responses? (Friedman 2002)
Leptin responses to weight loss and weight gain that led to either an increase or decrease in energy expenditure
Hedonic/Reward based influences? (Berthoud et al. 2011)
Humans do not simply eat to replace ‘fuel’ (metabolic need
Eating is pleasurable and rewarding
Evolutionary development backfiring
Hedonic systems in discrete brain areas
Moderated by homeostatic signals
Characters high higher cognitive and affective processes
- emotional state, social environment, past experience
The effect of lean mass on the drive to eat? (Blundell 2015)
Lean mass correlated to the amount we eat daily
Explains why men and muscle people eat more
The effect of resistance exercise on basal/resting metabolic rate?
Lean mass account for 2/3 of resting metabolic rate
There no effect of aerobic training
Resistance exercise increases muscle
What is the thermic effect of feeding?
Relates to energy expended during intestinal absorption, metabolism and storage
What is the thermic effect of fat?
2%
What is the thermic effect of protein?
20-30%
What is the thermic effect of alcohol?
20-30%
What is the thermic effect of carbohydrates?
5-10%
What percent of body mass is the liver?
2%
What percent of body mass is the brain?
3%
What perception of body mass is skeletal muscle?
50%
PAL level for highly inactive people?
1.4 PAL
PAL level for moderately active people?
1.7-1.99 PAL
PAL level for extremely active people?
> 2.4 PAL
How can physical activity be measured?
PAL levels
METS/hr/wk
How is physical acitivty measured?
Objective monitoring
Self-report
What makes up physical activity?
NEAT
Formal activity
What does NEAT stand for?
Non-exercise activity thermogenesis
What is the estimated energy expenditure during running? (kcal/kg/km)
1kcal/kg/km
What is the relationship between exercise intensity and energy expenditure?
There is a linear relationship between exercise intensity and energy expenditure
Energy cost is determined by distance covered and body mass
What causes a negative energy balance?
Reduce energy intake below requirements Maintain energy intake and increase energy expenditure Decrease energy intake and maintain energy expenditure Stern defence (adaptive thermogenesis/body mass)
What causes a positive energy balance?
Increase energy intake above requirements
Decrease energy expenditure and maintain energy intake
Maintain energy expenditure and increase energy intake
Little resistance - passive occurrence
The effect of a supportive environment on weight loss? (The Look Ahead Research Group 2014)
Weight decreases initially due to a highly supportive environment and motivation
Overtime weight increases
The effect of a supportive environment on weight loss and the body’s homeostasis defence? (Wadden 1993)
Weight decreases initially due to a highly supportive environment
The body initiates an adaptive response to promote weight gain after a period of weight loss
What is the effect of a supportive environment on weight change?
You are able to lose a significant amount of weight in a supportive environment
2/3 subjects gained weight in the follow-up
Define the dynamic equilibrium of weight loss?
Negative energy balance after an initial period of weight loss will begin to plateau very quickly due to compensatory responses
- reduction in basal metabolic rate
- NEAT
- change in diet-induced thermogenesis
Define adaptive thermogenesis (Reviewed by Dulloo et al. 2012)
Auto-regulatory mechanisms defending energy balance
Additional control beyond ‘body mass action’ effect
- basal metabolism - +/- 10% body weight change
- thermic effect of feeding - post obese
- spontaneous activity - NEAT
- muscular movement efficiency - cycling GME
The effect of weight loss on hedonic neural circuits? (Rosenbaum 2008)
Weight loss produces changes in neural circuit activation related to the hedonic regulation of food intake
Changes can be reversed by exogenous leptin
What are the responses to chronic overfeeding?
Increases with increases in lean mass, adipose and skeletal muscle
Diet-induced thermogenesis will increase
The energy cost of movement will increase
An increase in weight might lead to lethargy/fatigue
An increase in weight might lead to lower NEAT
How many kcal does skeletal muscle burn?
13.1kcal/kg/day
How many kcal does adipose burn?
4.5kcal/kg/day
For an obese male (50yrs) weighing 100kg who is 1.67m tall. Calculate how much weight this individual would expect to lose over 6 months (26wk) when restricting their diet by 500kcal/day and using the 3500kcal rule? (3500kcal results in a weight loss of 0.45kg/day)
= 3500kcal = 0.45kg/d weight loss
= 500 / 3500kcal = 14%
= 0.45kg x 0.14 = 0.0647kg/d weight loss
= 0.0647kg x 26wks = 11.7g weight lost
Why is there differences is a calculation of weight loss between different methods?
Some take into account that the rate of weight loss slows over time as metabolic compensation kicks in?
Calculate energy expenditure from 11.8METS and weights 70kg?
= 11.8 x 70kg = 826kcal/hr
= 826kcal / 60min = 13.76kcal/min
= 13.76kcal/min x 4.184kJ = 57.6kJ/min
How many kJ are expended at rest with 1kcal?
4.184kJ
How to calculate resting energy expenditure?
1kcal/kg/hr
What is the oxygen cost of the horizontal component of movement when walking?
0.1ml/kg/min
What is the oxygen cost of the vertical component of movement when walking?
1.8ml/kg/min
What is the oxygen cost of the horizontal component of movement when running?
0.2ml/kg/min
What is the oxygen cost of the vertical component of movement when running?
0.9ml/kg/min
How to convert mph to m/min?
x 26.82
How to convert m/min to mph?
x 0.03728
The equation to predict energy expenditure when exercising on a treadmill?
VO2 = resting component (resting VO2) + horizontal component + vertical component
What’s the value of VO2 at rest?
3.5mL/kg/min
How can 1MET also be expressed?
3.5mL/kg/min
What the calculation for the horizontal component of movement?
speed (m/min) x oxygen cost of the horizontal component
What the calculation for the vertical component of movement?
percent grade x speed (m/min) x oxygen cost of the vertical component
Calculate the energy cost of treadmill walking in VO2? A 90kg individual walk on a treadmill at 4.5km/h up a 4% grade?
VO2
= 3.5 + (75m/min x 0.1) + (0.004 x 75m/min x 1.8)
= 16.4mL/kg/min
What is 16.4mL/kg/min expressed in METS?
= 16.4mL/kg/min / 3.5
= 4.7METS
What is 16.4mL/kg/min expressed in kcal/min for a 90gkg person?
= (16.ml/kg/min x 90kg) / 1000 = 1.48 l/min
= 1.48 l/min x 5kcal/l = 7.4kcal/min
A 55g female runs for 30min at an intensity of 6.0 METS. Calculate the gross energy expenditure for this exercise bout?
55kg x 6 x 0.5h = 165kcal
Liraglutide is a synthetic version of which gut peptide which pharmaceutical companies developed for type 2 diabetes/obesity?
GLP-1
