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Flashcards in Week 1 Deck (54)
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1
Q

positive energy balance

A

following meal ingestion when nutrients are being distributed between tissues and stored for later use (nutrient excess; the fed state)

2
Q

negative energy balance

A

(the fasted state, illness or exercise) during which previously stored nutrients are mobilized to provide energy and substrates for metabolic processes.

3
Q

weight stability

A

When energy intake (kcal/day) equals energy expenditure (kcal/day) over long periods of time, weight is stable

4
Q

A typical adult consumes roughly ______ kcal per year with minimal weight gain. Over the next 35 years of your life an average adult will consume roughly ______ lbs of food and gain about __ lb per year.

A

1 million kcal/year

11,000 lbs of food

gain 1 lb/yr

5
Q

When does weight gain occur?

What is it due to?

A

When energy intake exceeds energy expenditure over a prolonged period

gain in weight is predominantly due to an increase in body fat which in turn predisposes to diseases such as hypertension, type 2 diabetes, some forms of cancer, coronary artery disease, degenerative joint disease, depression and other diseases.

6
Q

three components/parts of Total Energy Expenditure (TEE)

A

Resting Metabolic Rate (RMR)
Thermic Effect of Food (TEF)
Energy Expended in Physical Activity (EEPA)

7
Q

Resting Metabolic Rate (RMR)

A

-accounts for ~ 75% of total energy expenditure in sedentary people. -energy cost of Na+/K+ pumps, heart, keeping body temperature constant and other basic bodily functions.

8
Q

Primary determinant of Resting Metabolic Rate

A

The primary determinant of RMR is fat free mass (lean body mass). This is because organs such as the liver, heart, kidney, brain and skeletal muscle are the most metabolically active (energy and nutrient consuming).

9
Q

For 2 people with the same lean body madd/fat free mass, will their RMR be the exact same?

A

even for 2 people with the same lean body mass/fat free mass there is some variability in RMR. The cause of this variation is not known.

10
Q

How can resting metabolic rate be measured?

A

RMR can be measured by indirect calorimetry.
This is done with a device that measures respiratory gas composition and flow rates to estimate O2 consumption and CO2 production. Since cellular energy comes primarily from the oxidation of nutrients, the rate at which oxygen is consumed by a person at rest is an indirect measure of energy expenditure.

11
Q

How can Resting Metabolic Rate (RMR) be estimated?

A

RMR can be estimated from formulae using age, sex, height and weight. If lean body mass/fat free mass is known, this value can be added to the formulae for a more accurately estimate of RMR.

12
Q

Thermic Effect of Food (TEF)

A
  • accounts for ~ 8% of total energy expenditure.

- energy cost of digesting and distributing nutrients from the diet to tissues of the body.

13
Q

Do all nutrients have the same TEF?

A

No. Different types of nutrients vary in their TEF.

14
Q

Which has a higher TEF- fat, protein or carbohydrates?

A

Protein -highest energy cost of digestion
carbohydrate
fat- lowest TEF

15
Q

How can TEF be measured?

A

TEF can be measured by indirect calorimetry by determining the increment of energy expenditure above RMR following ingestion of a defined test meal.

16
Q

Components of Energy Expended in Physical Activity (EEPA)

A
  1. non- exercise activity thermogenesis (NEAT)

2. voluntary activity either in activities of daily living or in bouts of planned exercise

17
Q

What is the most variable component of energy exposure?

A

Energy Expended in Physical Activity (EEPA)

18
Q

How has EEPA changed over the last thousand years?

A

EEPA has dramatically declined for most humans through improvements in technology resulting in a decline in moderate intensity activities at work and at home.

19
Q

exercise/work efficiency

A

The ratio of work to total energy expended during physical activity

20
Q

How can total energy expenditure be measured most accurately?

A

method called “doubly labeled water” which measures oxygen consumption in free living individuals over a period of weeks. By subtracting RMR and TEF from TEE, EEPA can be estimated.

21
Q

Most people under-report food intake by:

A

20% to 40%, and is a bigger problem in people who are overweight or obese

22
Q

What do you know about a person if a person’s weight is stable and EI=TEE?

A

This means that a measure of total energy expenditure (such as doubly labeled water) accurately predicts energy intake if weight is stable.

23
Q

in a normal weight individual, what macronutrient store contains the greatest amount of stored energy?

A

Fat stores contain the greatest amount of stored energy, roughly 120,000 kcal (9 kcal/g, 13 kg fat in a 70 kg person) in a normal weight individual.

24
Q

How much carbohydrate is stored in the body?

A

Carbohydrate stores are roughly 2,000 kcal (4 kcal/g, 500g). These stores are mostly in the form of glycogen in muscle (400g) and liver (100g)

25
Q

What happens when a person is in persistently negative energy balance?

A

They will break down muscle protein to amino acids that can be converted by the liver to glucose to meet the fuel needs of the brain.

26
Q

What percent loss of body protein is associated with severe malnutrition?

A

A loss of 30% of body protein is associated with severe malnutrition at a point where death often results.

27
Q

The bulk of energy stores exist as ___ stores

A

fat

28
Q

Ways of estimating body fat stores

A

body mass index (weight in kg/height2 in meters)
skin fold thickness
bioelectrical impedance
body density measurements (by under water weighing or air displacement)
dual energy x-ray absorptiometry (DEXA).

29
Q

What is the most accurate way to measure body composition?

A

DEXA is the most accurate way to measure body composition.

30
Q

Is there a storage site for excess protein?

A

No. Protein that is provided in excess on the diet is oxidized in preference to carbohydrate or fat

31
Q

What will happen to a person in protein balance that is overfed in carbs and fat?

A

carbohydrate will be preferentially oxidized and fat will be stored. This occurs because of the smaller capacity for storing excess carbohydrate as glycogen. In addition, excess carbohydrate can be converted into fat providing more efficient long-term storage.

32
Q

What is the hierarchy of nutrient oxidation?

A

individuals in positive energy balance will tend to accumulate body fat. Protein preferentially oxidized first, then carbohydrate, then fat

33
Q

What is the most important thing to maintain in times of fasting?

A

if a person is in negative energy balance, the most important organ to sustain is the brain which requires an ongoing supply of glucose.

34
Q

When the body is in positive energy balance following the consumption of a meal, what is the primary task for the metabolic pathways?

A

To assimilate the ingested nutrients and fill storage pools such as triglyceride in adipose tissue or glycogen in muscle. This process of assimilation may involve the re-synthesis of polymers from the basic building blocks of each class.

35
Q

counter regulatory hormones

A

glucagon, cortisol, catecholamines, growth hormone

36
Q

Describe the energy state of the body between meals?

A

state of negative energy balance during which oxidizing tissues such as the liver, skeletal muscle, brain and kidneys must rely on stored nutrients for energy. During this period, stored nutrients are broken down into their component building blocks (glucose, fatty acids and amino acids) and these building blocks are then moved to these energy requiring tissues to meet their energy needs.

37
Q

In the fed state ____ is high, ____ is low and the task of the body is: ?

A

insulin

glucagon

ssimilate ingested nutrients.

38
Q

In a fasted state, ____ is low, ____ is high and the body is relying on what?

A

insulin

glucagon

previously stored nutrients.

39
Q

Anabolic

A

processes of building polymers from monomers

40
Q

Catabolic

A

pathways that break down complex molecules into their constituent parts.

41
Q

The process of gluconeogensis uses a range of carbon skeletons from other tissues including and the carbon skeletons from:

A
  • lactate (produced from glycolysis)

- amino acids that come from muscle

42
Q

Where is most glycogen stored?

A

Liver (400kcal) AND skeletal muscle (1600kcal)

43
Q

When the body enters a state of negative energy balance,_____ can provide an important, immediately available source of glucose for the brain and exercising muscle.

A

glycogen

44
Q

When is the pentose phosphate pathway (Hexose monophosphate shunt) activated?

A

when glucose is present in excess or there is a need for the molecules that the pathway produces. This pathway generates NADPH and ribose (5 carbon) sugars.

45
Q

What form is fat stored in the adipocyte?

A

triglyceride

46
Q

How can you make a fatty acid from AcetylCoA?

A

These two carbon building blocks can be put together to make fatty acids derived from glucose for storage in a process known as de novo lipogensis. These fatty acids can then be put together 3 at a time with the 3 carbon alcohol glycerol to make triglyceride,

47
Q

Why might the body utilize stored fat during negative energy balance?

A

adipose tissue can provide energy to oxidizing tissues such as skeletal muscle and liver as an alternative to glucose. This allows circulating glucose to be preferentially available to the brain which cannot oxidize fat directly.

48
Q

alternative source of fuel for the brain present following prolonged fasting and in the setting of uncontrolled type 1 diabetes.

A

ketone bodies (produced when insulin is very low and counter-regulatory hormones are very high)

49
Q

The important functions of amino acids:

A
  1. As structural components within proteins.
  2. As precursors for other important molecules such as neurotransmitters and hormones.
  3. As substrates that can be used for gluconeogensis.
  4. As nitrogen carriers.
50
Q

Urea Cycle

A

disposal of nitrogen derived from the metabolism of amino acids is the urea cycle. This is a multi-enzyme linked pathway that produces urea which enters the blood as “blood urea nitrogen” or BUN. This blood urea nitrogen is then excreted by the kidneys in the form of urine urea nitrogen.

51
Q

What is a normal Total energy expenditure?

A

25-35 kcal/kg/day

52
Q

Km of an enzyme

A

The substrate concentration at which the reaction is half maximal is the Km.

53
Q

What does a low Km indicate?

A

The substrate has strong affinity for the enzyme and the reaction will go at low substrate concentrations.

54
Q

What does a high Vmax indicate?

A

reaction that can produce a lot of product over a short period of time.