Chapter 6 - Energy Balance and Availability

Question 1

energy balance

Answer 1

balance between energy expenditure and energy intake

For the athlete, even short-term variations in energy balance (and, thus, in body mass) can have a dramatic impact on performance

Question 2

metabolizable energy

Answer 2

differences between the absolute energy of ingested food and any energy lost in feces and urine

The metabolizable energy of each macronutrient is approximately:
* 4 kcal/g for carbohydrate
* 4 kcal/g for protein
* 9 kcal/g for fat
* 7 kcal/g for alcohol

Question 3

thermic effect of alcohol

Answer 3

7 kcal/gram

Question 4

direct vs. indirect calorimetry

Answer 4

direct: necessitates use of a process called direct calorimetry and highly controlled lab conditions

indirect: the type and rate of substrate utilization are measured from gas exchange measurements (carbon dioxide production and oxygen consumption) during both rest and steady state exercise

Question 5

examples of CSNC-available calorimetry estimate equations

Answer 5

1. Harris Benedict
2. Mifflin-St. Jeor
3. Activity Factors (AF) (Multiply BMR x AF to get Estimated Energy Requirements (EER)

Little to no exercise: EER = BMR x 1.2 (for in bed); for out of bed but low activity, use 1.3
**Light exercise **(1–3 days/week): BMR x 1.375
Moderate exercise (3–5 days/week): BMR x 1.55
Heavy exercise (6–7 days/week): BMR x 1.725
Very heavy exercise (e.g., 2 workouts/day; intense workouts or athletic training): EER = BMR x 1.9

Question 6

components of energy expenditure

Answer 6

1. BMR (RMR) (60-70% of TDEE for basic physiological functions)
2. excercise activity thermogenesis (~30% for average athletes)
3. ** thermic effect of food** (~10% of TDEE)

Question 7

component of energy expenditure

resting metabolic rate

Answer 7

1. largest component of energy expenditure (60-70% of TDEE)
2. Different tissues within the body have distinctly different resting energy requirements. For example, organs such as the liver, gut, brain, kidney, and heart have high energy requirements and account for approximately 75% of resting metabolic rate.

Despite skeletal muscle comprising almost 40% of total body weight, muscle has a much lower energy requirement than these vital organs and comprises only 20% of resting metabolic rate

Question 8

component of energy expenditure

activity thermogenesis

Answer 8

1. activity and non-activity thermogenesis
2. by far the most variable component of daily energy expenditure
3. 30% of total daily energy expenditure and, in some cases, can be as high as 70–80%

Question 9

energy availability

Answer 9

Energy availability = (Energy intake – exercise energy expenditure) ÷ fat-free mass

example with a cyclist:

Energy intake (8,000 kcal) – exercise energy expenditure (5,600 kcal) / fat-free mass (70 kg)

Energy availability = (8,000 – 5,600) / 70

Energy availability = 2,400 / 70 = 34.3

EA = 34.3

Question 10

daily energy balance vs daily energy availability

Answer 10

Question 11

optimal energy availability in athletes

Answer 11

Though optimal levels of energy availability in athletes are not currently known, an energy availability of
1. 45 kcal/kg fat free mass (FFM) per day for females
2. 40 kcal/kg FFM per day for males

provides a threshold to maintain normal physiological function

Question 12

low energy availability (LEA)

Answer 12

A state in which insufficient energy is available for normal physiological functions

Question 13

amenorrhea

Answer 13

The absence of menstruation

Question 14

functional hypothalamic amenorrhea (FHA)

Answer 14

A form of amenorrhea and a chronic absence of ovulation

athletes who compete in weight-sensitive sports and/or sports that require high levels of energy expenditure seem to be at higher risk of LEA. In contrast, LEA is less prevalent in athletes who compete in sports where daily energy requirements are significantly lower and there is less importance placed on overall body size and composition

Question 15

consequences of LEA

Answer 15

1. Disruptions to reproductive function and sex hormone production
2. Increased risk of low bone mineral density
3. Alterations in metabolic rate
4. Reduced psychological well-being
5. Reductions in performance

Question 16

menarche

Answer 16

first occurence of menstruation

Question 17

consequences of LEA

reproductive dysfunction

Answer 17

LEA reduces sex hormones associated with fertility in both male and female athletes

females may experience a delayed menarche

Question 18

consequences of LEA

impaired bone health

Answer 18

reduced bone mineral density, decreased estimates of bone strength, and increased risk of bone stress injuries

Question 19

consequences of LEA

alterations to metabolic rate

Answer 19

LEA is also associated with a reduction in RMR in both female and male athletes

For example, a 2019 case study following the weight-making practices of a professional MMA fighter reported a 330 kcal reduction in resting metabolic rate after just 7 weeks of reduced energy availability

Question 20

consequences of LEA

cardiovascular function

Answer 20

Sustained LEA causes changes in circulating hormones that have a direct impact to cardiovascular health

Question 21

consequences of LEA

GI issues

Answer 21

Chronic periods of energy deficiency are thought to cause atrophy of mucosal tissue within the intestine, which manifests into various gastrointestinal issues such as bloating, cramping, and constipation

Question 22

consequences of LEA

immunity

Answer 22

The immune system may also be altered by LEA, which may cause athletes to miss more training days

For example, observational studies of elite athletes presenting with LEA report an increased likelihood of illnesses, body aches, and head-related symptoms

Question 23

consequences of LEA

hematological issues

Answer 23

Poor iron status is often associated with LEA.

Question 24

consequences of LEA

growth and development

Answer 24

Alternations in hormones that play an important role in growth and development, such as growth hormone and insulin-like growth factor (IGF-1), have been observed in amenorrheic athletes

As a result, sustained periods of LEA may potentially impair the maturation of youth athletes

Question 25

# consequences of LEA performance

Answer 25

In addition to the observed health effects of LEA, performance can also be negatively impacted through indirect mechanisms such as **reduced recovery and muscle function impairment.**

Question 26

# consequences of LEA psychological issues

Answer 26

Various aspects of psychological well-being can also be impacted by LEA female athletes who present with FHA have been found to have a **higher incidence of mild depressive traits, social insecurity, and fears of weight gain**

Question 27

calculate energy availability

Answer 27

Energy availability = (Energy intake – exercise energy expenditure) ÷ fat-free mass ## Footnote Using the example of the cyclist above, the following calculates the rider’s energy availability: Energy intake (8,000 kcal) – exercise energy expenditure (5,600 kcal) / fat-free mass (70 kg) Energy availability = (8,000 – 5,600) / 70 Energy availability = 2,400 / 70 = 34.3 EA = 34.3

Question 28

energy availability categories

Answer 28

TABLE: Energy Availability Categories Energy Availability Male/Female **High** Above 40 kcal/kg FFM Above 45 kcal/kg FFM For healthy weight gain or maintenance **Optimal** Above 40 kcal/kg FFM Above 45 kcal/kg FFM For weight maintenance providing adequate energy for all physiological functions **Subclinical** 30–40 kcal/kg FFM 30–45 kcal/kg FFM May be tolerated for short periods during a well-constructed weight loss program **Clinical** Below 30 kcal/kg FFM Below 30 kcal/kg FFM Note. Units for Male and Female measures above in kcal/kg FFM.

Question 29

Harris Benedict Equation for BMR

Answer 29

**Men**: BMR = 88.362 + (13.397 x weight in kg) + (4.799 x height in cm) – (5.677 x age in years) **Women**: BMR = 447.593 + (9.247 x weight in kg) + (3.098 x height in cm) – (4.330 x age in years) ## Footnote components are: **weight in kg height in cm age in years**

Question 30

activity factors for varying leves of exercise | 5 total categories

Answer 30

*** Little to no exercise**: EER = BMR x 1.2 (for in bed); out of bed but low activity, use 1.3 * **Light exercise** (1–3 days/week): BMR x 1.375 * **Moderate exercise **(3–5 days/week): BMR x 1.55 * **Heavy exercise** (6–7 days/week): BMR x 1.725 * **Very heavy exercise** (e.g., 2 workouts/day; intense workouts or athletic training): EER = BMR x 1.9

Question 31

EER equation (estimated energy requirement)

Answer 31

activity factor x estimated BMR

Question 32

thermic effect of food

Answer 32

increased energy expenditure in response to digestion, absorption, metabolism, and storage of food ## Footnote **fat storage as adipose tissue**: approximately 3% of the energy of the ingested meal **carbohydrate storage as glycogen**: requires up to 7% **Protein synthesis and breakdown**: approximately 24% of the available energy

Question 33

screening athletes for LEA

Answer 33

1. **subjective symptoms** - low mood, irritability, and feelings of fatigue 2. **body composition** - excessively low body fat for prolonged periods or massive weight-loss in a short period 3. **clinical assessment** - can be used to identify hormone defficiencies

Question 34

treating LEA

Answer 34

CSNCs use a combination of 1. increased energy intake 2. decresed energy expenditure ## Footnote they typically vouge for the former because decreasing training load can result in detraining effect

Question 35

What percent of high school female athletes regularly skip meals to lose weight?

Answer 35

23%

Question 36

What appears to be responsible for LEA among high school athletes?

Answer 36

ideal body type