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FNH 350 > Energy Metabolism > Flashcards

Energy Metabolism Flashcards

1
Q

Energy Balance

A

Energy input = Energy output
Energy intake = energy expenditure

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2
Q

Negative Energy Balance

A

the body does not meet its energy requirements through diet

energy intake < energy expenditure for basal function
- loss of adipose tissue
- loss of muscle
- weight loss

Causes:
- insufficient food availability
- anorexia nervosa
- bulima nervosa
- cancer

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3
Q

Anorexia

A
  • highest -> psychiatric disorder
  • onset -> pre- or postpuberty; possible at any age
  • more females
  • preoccupation with food, refusal to healthy body weight
  • weight loss -> excessive dieting and exercising
  • damage occurred in various tissues and organs, loss of hairs, change in skin colour, teeth/bine degradation, organ failure
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4
Q

Bulimia Nervosa

A
  • life-threatening eating disorder
  • binging and purging; forced vomiting or excessive exercise
  • preoccupation with body shape and weight; fear of gaining weight; feeling of uncontrolled eating behaviour; eating until the point of discomfort or pain
  • risk: female, young age, family history, psychological and emotional issues, performance pressure in sports
  • health problems: dehydration, heart failure, amenorrhoea, anxiety
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5
Q

Female Athlete Triad

A

A syndrome of 3 interrelated conditions:
- disordered eating
- irregular menstruation
- low bone density

How does it develop:
- excessive exercise combined with eating disorder -> irregular menstruation -> associated w/ low estrogen levels and results in low bonded density

Manage the disorder:
- reduce preoccupation w/ foods, weight, body fat
- inc. meals and snacks to the appropriate amount
- achieve weight for height
- dec. training time and/or intensity by 10-20%

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6
Q

What is Relative Energy Deficit in Sport?

A

a syndrome of poor health and declining athletic performance that happens when athletes do not get enough fuel through food to support the energy demands of their daily lives and training

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7
Q

Positive energy balance

A

Energy input > energy output
- gain of adipose tissue
- gain of muscle and bone tissue
- weight gain
- overweight, obesity

Causes:
- excessive caloric intake
- too little energy output for the amount of caloric consumed
- genetic/biochemical mechanisms

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8
Q

What are the potential mechanisms for regulating body weight and composition?

A
  1. Dietary composition
  2. Portion size and frequency of meal consumption
  3. food intake regulation/satiety
  4. Genetic influences
  5. Exercise
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9
Q

Dietary composition

A
  • high-fat food products
  • sweetened beverages
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10
Q

Portion size and frequency of meal consumption

A

Obesity-related to larger portion sizes of main meals
- omitting meals -> gain weight

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11
Q

food intake regulation/satiety

A

Hormones => hypothalamus -> connecting nervous system and endocrine system
Two groups of neurotransmitters:
1. melanocyte-stimulating hormone (MSH) => dec. hunger -> cholecystokinin, insulin, leptin -> stimulate the release
2. neuropeptides Y (NPY) and agouti-related protein (ARP): inhibits MSH -> inc. hunger -> Ghrelin -> stimulate the release of them

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12
Q

Leptin

A
  • secreted by adipose tissue
  • stimulates MSH; dec. hunger
  • leptin receptors “defective” in obese people
    -> No suppression of hunger by elevated leptin levels
  • weight loss -> dec. leptin -> response to starvation
  • weight gain -> inc. leptin -> response to obesity
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13
Q

Genetic influences

A

Melanocortin receptor (MSH = a melanocortin) => defect leads to loss of regulation for hunger -> obesity

Fat mass and obesity-associated gene (FTO) => polygenic effect on obesity: variation in FTP strongly contributes to early onset

Heritability: body weight and composition

Leptin receptor

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14
Q

Exercise

A
  • can lead to a negative energy balance
  • beneficial for obese/overweight individuals; detrimental for individuals with eating disorders
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15
Q

Methods for measuring body composition focus on two compartments

A
  1. Fat mass => triacylglycerols, other lipids, little water, electrolyte
  2. Fat-free body mass => water, muscle, bone, connective tissue, organs
    - lean-body mass => fat-free plus essential fats
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16
Q

what are the compartments:

A
  • Density
  • Ability to conduct an electrical current
  • Electrolytes content
  • X-ray density
17
Q

Methods to measure fat-free mass

A
  • Total body water
  • bioelectrical impedance analysis
  • dual-energy x-ray absorptiometry
18
Q

Methods to measure fat mass

A
  • Anthropometry
  • densitometry
  • dual-energy x-ray absorptiometry
19
Q

Anthropometry

A
  • **caliper to measure skin fold thickness **
  • direct relationship between total body fat and fat deposited beneath the skin
  • higher potential error
    waist circumference and waist/hip ratio
  • both correlate with visceral fat
  • both associated w/ CVD risk
  • waist/hip less accurate
  • waist circumference => predictor for risk of heart disease, stroke, high blood pressure, high blood cholesterol, type 2 diabetes
20
Q

Densitometry

A

underwater weighing = measurement of body fat
Advantage:
- non-invasive
- precise

Challenging:
- high equipment cost
- extreme cooperation and time required of subjects
- not suitable for young children, older adults, unhealthy people

calculation based on the assumption
- fat mass has no constant density; consists of different components that have different densities (bone, muscle, organs, etc)
- leads to errors in calculating body fats

21
Q

Absorptiometry

A

Dual photon absorptiometry and Dual-energy x-ray absorptiometry (DEXA, DXA)
- measures the attenuation of X-rays while passing over the body
- flux of x-ray -> across the fat and fat-free masses
- correlated w/ other body composition methods => estimation of %, fat mass, fat-free mass, bone mineral density

Challenge:
- high equipment cost, trained personnel, inaccurate for patients w/ metal implants

22
Q

Bioelectric Impedance Analysis

A

Measurement of electrical conductivity in the body:
- instrument induces -> electrical current
- measures proportional to electrolytes and water content
- electrolytes are mostly associated w/ lean body mass
Challenges:
- expensive, readings affected by hydration and electrolyte imbalance

23
Q

Total Body Water

A

use of stable isotope labelled water (D2O)
Principle:
- injection/ingestion of labelled water
- distribution of isotope in body water (w/in 2-6hours)
- measurement of labelled water in body fluids

calculation = based on the assumption that water content of lean body mass = 73%

challenge:
- requires trained personnel
- hydration status impacts results
- degree of hydration in lean tissue carried considerably
- adipose tissue contains 15% water by weight

24
Q

BMI

A
  • inexpensive and simple
  • used for the classification of a person’s risk of developing health problems
  • does not directly measure body fat -> indirect parameter for body fat
    methods -> underwater weighing and dual-energy x-ray absorptiometry (DXA)
25
Q

Basal Metabolic Rate (BMR)

A

energy to sustain basic life: respiration, heartbeat, renal function, muscle tone, blood circulation
- organs

26
Q

How is BMR assessed?

A

Measurements of consumed O2 and produced CO2 under standardized conditions:
- postabsorptive state (12-14 hours after last food intake)
- done -> after awakening
- lying down
- relax, motionless awake
- comfortable temperatures
BEE = Basal energy expenditure

27
Q

Resting metabolic Rate (RMR)

A

Measurements under similar conditions as for BMR - no food intake or exercise 4-5 hours before test
- 10% higher than BMR
- 65-80% of daily total energy expenditure
Resting Energy Expenditure (REE)

28
Q

What are the factors influencing BMR/RMR?

A

Age and body composition:
- highest BMR during infancy -> dec., w/ maturation
- REE infant > REE children (inc, bone and muscle tissue)
- adults -> dec. in active tissue and inc. in fat mass during aging

Gender:
- higher for men

Physiological state: pregnancy, fever, hyperthyroidism, fasting, menstrual cycle

29
Q

Thermic effect of food

A
  • inc., heat production following food ingestion
  • inc., energy expenditure associated w/ food processing including digestion, absorption, active transport, metabolism, storage of energy from ingested food
  • 5-30% inc. in energy expenditure
    protein (20-30%) > carbs (5-10%) > fats (0-5%)
30
Q

What is thermoregulation?

A

Regulatory thermogenesis = change in metabolism to maintain or restore the body’s core temperature -> alternation in energy expenditure
- normal body temperature
- diurnal change => lower temp in morning; higher evening
- temp maintained in central core (brain, central nervous system, organs
- temperature varies => skeletal muscle/skin arterioles/sweat glands to relate the core

environmental temperature < thermoneutral/comfort zone
-> heat generation; inc. energy expenditure
-> hypothermia -> metabolic processes are slowed down -> fatigue, disorientation, depression of heart/lung activity

**environmental temperature > thermoneutral/comfort zone **
-> overfeeding, trauma, burns
-> reduced muscle tonus, sweating
-> hyperthermia-> failed thermoregulation

31
Q

physical activity

A

voluntary movement
- variable of all energy expenditure
- 20-40% total energy expenditure
- factors impacting energy expenditure: intensity, duration, frequency of activity
- remain elevated after activity for a short period

32
Q

What are methods to assess energy expenditure?

A

calorimetry: determination of body heat loss
1. direct calorimetry
2. indirect calorimetry

33
Q

Direct calorimetry

A

Measurement of heat dissipation (loss) from the body by isothermal principle
- sensible heat loss (water temp.)
- heat from water vaporization (moisture in chamber air)
- energy loss of urine/feces

Limitation:
1. Expensive ($1 million)
2. Laborious
3. Discomfort for subject

ex. miners
- impacts of mining activities and underground temperatures on body heat
- prevents heat stress; efficient ventilation infrastructure in mines

34
Q

Respiratory quotient

A

measurement of consumption of O2 and expiration of CO2
RQ = CO2/O2
Carbs -> RQ= 1.0
Fat -> RQ = 0.7
Protein -> RQ = 0.8
RQ=0.82 -> metabolism of a mixture of 40% CHO and 60% FAT
RQ > 1 -> hyperventilation and acidosis (excessive exercise)

35
Q

Indirect calorimetry

A
  1. Respiratory quotient
  2. Doubly Labelled water
36
Q

Doubly Labelled water

A

addition of a known amount of a stable isotope labelled substance to the analyzed sample allows measuring the quantity of pool ratio

Participants receive labelled water in the morning -> whole body water pool w/in 5 hours -. disappearance measured in blood and urine

measurements of turnover rate (‘flux’)
- loss of labelled oxygen H218O or C18O2 -> water turnover and loss labelled hydrogen
- loss of labelled hydrogen as 2H2O-> turnover alone
Difference in H218O flux and 2H2O flux = CO2 produced

limitation and sources of error of this method:
- use of food records -> risk of underreporting
- calculation of oxygen consumption from food quotient
- high cost to labelled oxygen, clinical staff, analytical infrastructure
- duration of participant involvement

FNH 350 (6 decks)

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