Lecture 2 - energy balance and exercise

Question 1

3 main components of energy balance

Answer 1

1) energy intake
2) energy expenditure
3) energy stores

Question 2

Energy balance

Answer 2

Nutrition and activity interact to influence body mass and composition.

Question 3

kcals in 1 kilo of body fat (adipose tissue, protein, water)

Answer 3

7700kcal

*To gain 1 kilo of fat in 1 year you need to overconsume 20kcal a day

Question 4

Negative energy balance

Answer 4

Increase energy expenditure while maintaining intake or reduce intake but maintain expenditure - lose weight

Question 5

Positive energy balance

Answer 5

Increase energy intake and maintain expenditure or decrease expenditure and maintain intake - gain weight

Question 5

Sedentary individual’s EE %

Answer 5

70% = RMR
10% = DIT (dietary induced thermogenesis - energy expenditure required to process food to maintain energy balance)
20% = TEE (thermic effect of exercise - energy expended due to activity, food intake and maintaining bodily functions)

Question 6

how many Kcals in 8MJ and 20MJ

Answer 6

8 MJ = 2000kcal (4.18 Joules in a calorie
20 MJ = 5,000 Kcal

Question 7

EE in a very active person

Answer 7

In a very active person, RMR makes up much less of the total EE, but it is still the same in total as a sedentary individual (the same absolute amount). It won’t change (irrelevant of activity).
- DIT (consuming, digesting, absorbing, assimilating all the nutrients from the diet) makes up the same proportional amount, but absolute amount increases. Requires 2 X more energy to digest 2 x the amount of the food
- DIT is the most malleable component of EE

Question 8

Energy intake

Answer 8

CHO : 4kcal.g-1 / 17 KJ.g-1
Lipid (fat): 9kcal.g-1 / 37 KJ.g-1
Protein: 4kcal.g-1 / 17 KJ.g-1
Alcohol: 7kcal.g-1 / 29 KJ.g-1

*there is no storage form of alcohol - Ethanol is oxidised

Question 9

Energy stores (for 70kilo person with 15% body fat)

Answer 9

Liver glycogen: 0.1kg / 400 kcal
Muscle glycogen: 0.4 kg / 1600kcal
blood glucose: 0.01 kg / 40 kcal
Fat: 10.5 kg / 94,500 kcal
Protein: 12 kg / 48,000 kcal

*CHO reserves in muscle and liver glycogen. Muscle glycogen is available quickly but protein is hard to access

Question 10

how much sugar circulates the blood at any one time

Answer 10

1 Tsp

Question 11

Energy balance (EB) vs energy availability (EA)

Answer 11

• EB = Dietary energy – Total energy expenditure
• Difference between intake and expenditure
• EB is an OUTPUT from the body’s physiological systems
• EA = Dietary energy intake – Exercise energy expenditure
• More of an input than EB
• EA is an INPUT to the body’s physiological systems
• As an athlete the training is going to happen

Question 12

General EA recommendations:

Answer 12

Growth/ CHO loading: >45kcal/ kg lean body mass
Weight maintenance: ~45 kcal/ kg leans body mass
Weight loss: 30-45 kcal/ kg body mass

Question 13

Causes of LEA in athletes:

Answer 13

• Compulsive eating disorders
• Intentional efforts to improve performance by reducing body weight and body fat (purposeful weight loss e.g., meeting a weight category)
• Inadvertent failure to match energy intake to energy expenditure (accidental)

Question 14

Exercise and appetite regulation

Answer 14

• Total PYY (satiating hormone – opposite to ghrelin)– exercise amplifies this satiating signal
• Acylated ghrelin (hunger hormone: high before meals/ low after meals – exercise supressed this hunger hormone
• “Appetite hormones” respond in a manner that should supress hunger/ food intake
• With rest Ghrelin stayed high, but exercise supresses ghrelin – exercise hormonally suggests a reduction in energy requirements

Question 15

Exercise and short term energy intake

Answer 15

• Short term energy intake is unchanged after exercise
• Prolonged exercise lowers short-term energy availability
• Although exercise indues an energy deficit it doesn’t increase the amount of food people voluntarily eat
• Exercise supresses net energy intake on the whole

Question 16

Exercise and energy intake (Barutcu et al 2021)

Answer 16

• Net effect of exercise is still a reduced energy balance
• In advance of exercise, people choose to eat a little bit more (they don’t eat more in response to exercise). They still don’t eat enough to compensate for the exercise
• Exercise could inadvertently lead to individuals not eating enough – in an exercise scenario this is not positive
• Long term leads to LEA

Question 17

Inadvertent energy deficiency (Stubbs et al 2004):

Answer 17

• Made men expend 8,400 kilocalories each day and allowed them to eat as much as they want
• 8 lean men living in a laboratory eating ad-libitum
• Total EE (measured in a lab) decreased every single day.
• If total EE decreases, but EEE stays the same and EI stays the same, it will show that other systems wont use as much energy
• Demonstrates suppression of energy expenditure by bodily systems due to energy deficit e.g., symptoms that maintain body temperature, hormone production, bone health, muscle protein turnover etc
• Negative energy balance – subtracting energy from other systems does not save the total EE
• This is now termed RED-S – the suppression of energy expenditure by bodily systems due to energy deficit.

Question 18

REDs - relative energy deficiency in sport (Mountjoy)

Answer 18

*Impaired reproductive function
*Impaired bone health
*Impaired gastrointestinal function
*Impaired energy metabolism/ regulation
*Impaired haematological function
*Urinary incontinence
*Impaired glucose and lipid metabolism
*Mental health issues
*Impaired neurocognitive function
*Sleep disturbances
*Impaired cardiovascular function
*Reduced skeletal muscle function
*Impaired growth and development
*Reduced immunity

Question 19

Lecture summary:

Answer 19

• EA and EB can be used as guides to facilitate athlete alterations in body mass/ composition and monitor athlete health. EA and EB are the key tools to elicit change in body mass/ composition
• Appropriate EB is required to achieve desired outcome, but must consider EA to optimise health outcomes. If you don’t expend more energy than you consume you will not lose weight (long term).
• To reduce EE, focus on protein post exercise may contribute to this/ increase EE by focus on CHO’s?