Week 6 obesity 2

Question 1

What are the principles of human energy balance?

Answer 1

The 1st law of thermodynamics - energy can be transferred from one system to another but cannot be created or destroyed

Thermodynamic laws apply to the body as per any isolated item

Chemical EN in must equal the output of heat, mechanical work and chemical EN used in biosynthetic reactions; any chemical energy remaining will be stored.

Question 2

What is energy balance?

Answer 2

Energy intake = energy expended + energy stored

Question 3

What has evolutionary biology ensured about the energy balance?

Answer 3

The system is biased because the body will much more rigorously defend against negative energy balance to protect from starvation.

Question 4

Why is it easier to control energy balance through energy input than output?

Answer 4

Only approx. 20% of energy is through movement/physical output so easier to control energy balance by altering food intake.

Question 5

What is the body’s response to negative energy balance?

Answer 5

Hungry

Thoughts/consciousness of food around you increases

Heightened sense of smell

Stresses/anxious

Question 6

What is meant by setpoints?

Answer 6

Somewhere within our body/brain there is a setpoint - monitors energy balance

If we go into negative energy balance it will elicit responses to try and make you move back into a positive energy balance.

however this is based on circumstantial evidence, not tangible

Question 7

What is leptin?

Answer 7

Secreted from subcutaneous fat in proportion to how much fat we have stored - tells the brain about energy resources.

If you go into negative energy balance, levels of leptin will drop - solicits responses to try and put you back into positive energy balance.

Question 8

What is adaptive thermogenesis?

Answer 8

If in a negative energy balance, basal metabolic rate will plummet - goes down further than what would be proportional to the amount of tissue lost (another evolutionary mechanism to survive famine).

Question 9

3500Kcal is thought to equate to around how much fat?

Answer 9

1 pound

Question 10

What is dynamic equilibrium?

Answer 10

Energy deficits trigger compensatory changes;
- decreased basal metabolic rate
- decreased diet induced thermogenesis because eating less food
- become more lethargic
Therefore not feeling as good so less likely to be active so energy deficit narrows and eventually weight loss will plateau

Question 11

What is meant by substrate metabolism hierarchy?

Answer 11

The body will metabolise different macronutrients in a different order because of the differences in storage capacity of the different macronutrients and also the effect of macronutrients on dietary induced thermogenesis.

Question 12

Why does the body deal with alcohol before anything else?

Answer 12

Alcohol is a toxin

We have no storage capacity for alcohol so the body burns it before it even looks at the food consumed (alcohol is 7Kcal per gram)

Energy used to burn alcohol is quite considerable

Question 13

What is the ranking of oxidative priority?

Answer 13

1) Alcohol - no storage space
2) Protein - limited storage space (plasma/tissue)
3) Carbohydrate - blood (glucose) glycogen storage
4) adipose storage

Question 14

Summarise 4-6hr DIT for alcohol, protein, carbohydrate and fat

Answer 14

Alcohol - 15%
Protein - 25%
CHO - 8%
Fat - 3%

Question 15

How much carbohydrate do we typically store?

Answer 15

Approx 500g across liver/muscle (but can change with training)

Question 16

Summarise energy and substrate metabolism during exercise

Answer 16

As intensity increases, energy expenditure rate increases

As body weight increases, energy expenditure in PA increases because it costs more energy to move a larger mass (not to the same extent in non weight bearing activities).

Question 17

What is the approximation for calculating EE in running?

Answer 17

1Kcal / Kg / Km

e.g. 90Kg individual running 5k = 450Kcal (gross)

Question 18

Summarise the relative contribution of substrates to metabolism during exercise in healthy humans

Answer 18

Different intensities / durations will effect the substrate that is metabolised

At low intensity fat predominates

This decreases as CHO metabolism increases as intensity increases

Question 19

What is suggested to be the maximum rate of fat metabolism?

Answer 19

64-65% VO2 max

Question 20

What is the impact of feeding vs fasting on substrate metabolism?

Answer 20

Exercising in a fasted state will increase the amount of fat metabolised because insulin levels are low which allows lipolysis to proceed

Consuming a carbohydrate meal up to 3hrs before exercising will suppress fat oxidation

Question 21

What did Lee et al (2005) say about exercising without losing body mass?

Answer 21

It is still an effective strategy for obesity reduction in obese individuals with and without T11 diabetes. There are quite often still reductions in body fat.

Question 22

Neuro-humoral appetite control system (homeostatic) - what are episodic signals?

Answer 22

Function on a meal to meal basis to try to help us regulate what we eat.

E.g. hormones such as grenin which increase throughout the day to tell us we’re hungry, we eat, grehlin levels go down (GLP does the opposite).

Question 23

Neuro-humoral appetite control system (homeostatic) - what are tonic signals?

Answer 23

Tell the brain about stored energy

E.g. leptin tells the brain about how much stored energy is in the body

Question 24

How do tonic and episodic signals travel around the body?

Answer 24

These signals travel via the circulation and the vagus nerve and they interact within the hypothalamus (acute nucleus)

Question 25

Summarise exercise, appetite and gut hormones

Answer 25

Moderate to high intensity exercise transiently suppresses appetite

Associated with alterations to circulating hormones (e.g. grehlin, PYY, GPL-1)

Does not automatically stimulate appetite, even if hunger is high

Question 26

What were the key findings in the study by Stubbs et al (2002) which involved 6 young lean women undertaking moderate and high volume exercise over 7 days with a very low calorie intake?

Answer 26

Increase in appetite and cravings

Partial increase in energy intake

Energy balance still negative

Initial compensatory adjustments

If continued, energy balance will be re-established at a lower body weight.

Question 27

What is non exercise activity thermogenesis?

Answer 27

Defined as the energy expenditure of all physical activities other than volitional exercise, such as the activities of daily living, small muscle movements, spontaneous muscle contraction and postural maintenance.

Question 28

What are some conclusions that have been drawn about NEAT?

Answer 28

NEAT makes a significant contribution to total daily EE

Can be measured using accelerometers or derived from measures of total daily EE

In young, healthy individuals exercise training does not seem to induce a compensatory decline in NEAT.

High volume of exercise training may stimulate a compensatory decline in NEAT in older adults.

Question 29

What is EPOC?

Answer 29

Excess post exercise oxygen consumption

Question 30

What have recent studies suggested about EPOC?

Answer 30

The amount of energy you burn in the hours after exercise is actually minimal (equates to about no more than 20Kcal)

If consumed more food, DIT may explain the augmented EPOC

Question 31

Summarise Diet induced thermogenesis

Answer 31

The increase in energy expenditure above basal fasting level divided by the energy content of the food ingested and is commonly expressed as a percentage

The intestinal absorption of nutrients, the initial steps of their metabolism and the storage of the absorbed but not immediately oxidised nutrients.

Represents about 10% of the total amount of energy ingested over 24hrs

Not affected by exercise

Question 32

What is the problem with weight loss medication and how can this problem be attenuated?

Answer 32

When you lose weight through dieting about one third of the mass you lose is mean skeletal muscle mass.

Studies have shown that exercise attenuates lean mass loss during weight reduction (particularly resistance training).

Question 33

What have animal studies shown high level of PA to be associated with?

Answer 33

Inhibited growth and repair

Decreased reproductive activity

TDEE no different between primates in the wild vs primates in captivity