MACROS & ENERGY EXPENDITURE Flashcards
(35 cards)
Define energy balance and outline the different factors
affecting energy expenditure.
Energy balance: energy intake (calories consumed) and energy expenditure (calories burned); determines weight maintenance, gain, or loss
BMR, TEF, PA, NEAT
Basal Metabolic Rate (BMR)
Energy (ATP) needed for basic functions at rest; estimates minimum number of calories needed to function
Thermic Effect of Food (TEF)
Energy used for digestion, absorption, and metabolism (~10-35% of daily energy/calories); AKA Dietary induced thermogenesis (DIT)
Reaches max 1 hour after meal
Obese people have low DIT
** for physically active people, DIT is a small portion of TDEE (<10%)
1) obligatory thermogenesis: energy requiring processes of digesting, absorbing, and assimilating food
2) facultative thermogenesis: increased activation of sympathetic nervous system leading to increase in energy metabolism
Physical Activity (PA)
Includes both structured exercise and daily activities (ADLs)
greatest change/variation in energy expenditure (can choose to do it to burn more calories)
key components: *intensity and duration
Vigorous exercise can increase EE 10x above resting values
Accounts for 15-30% of TDEE
Non-Exercise Activity Thermogenesis (NEAT)
Energy from activities like fidgeting and standing.
Increasing NEAT while increasing kcal intake allows resistance to weight gain
What are some energy consuming processes? (uses ATP)
- breathing, digestion, muscle tone
- gene expression (transcription of genes to make new proteins)
- breaking down proteins into amino acids
What are the physical activity guidelines?
150 – 300 mins/wk of moderate intensity aerobic activity
OR
75 – 150 mins/wk of vigorous intensity aerobic activity
OR
A combination of both, but in addition to:
2x/wk Muscle strengthening (resistance training) exercises of all major muscle groups at moderate or greater intensity.
Active = 500-1000 MET minutes
What percentage of adults meet the PA guidelines?
25% men, 20% women
Exercise intensity scale
RPE = RATE OF PERCEIVED EXERTION (Borg)
Sedentary -> sitting, 1-2 RPE, VO2 max <37, %HR max <40, <1.5 METs
Light -> light walking, 3-4 RPE
Moderate -> brisk walking/jogging, 5-6 RPE
Vigorous -> running, 7-8 RPE
Maximal -> sprinting, 9-10 RPE, VO2 max >91, %HR max > 93, >9 METs
Define METs and understand the importance.
Metabolic Equivalent of Task (MET) is a unit used to estimate the energy cost of physical activities. 1 MET = resting energy expenditure (≈3.5 mL O₂/kg/min).
Importance:
Helps compare the intensity of different activities.
Used in exercise prescription and energy expenditure calculations.
Higher METs indicate greater energy expenditure.
METs defined as multiples of the RMR
One MET = 3.5 mL O2 / kg BW / min
Two METs = 7 mL O2 /kg BW / min
1 L of oxygen consumed = 5kcal (5kcals/LO2)
lbs to kgs = BW lbs / 2.2 kgs
Calories burned based on MET level
(METS x 3.5 x BW kg)/200
answer x minutes
How much exercise is enough for improving healthspan and reducing disease risk?
J shaped curve: health risk compared to exercise training volume
Current guidelines (30 min per day) will reduce risk by half
High volume is around 20 hours per week and has greatest benefit (low risk of disease)
Can be too extreme at highest volume (extreme exercise hypothesis)
How many MET minutes correspond to each activity level/hazard ratio?
Graph of hazard ratio over MET minutes per week
Inactive - 0 MET, 1.0 hazard ratio
Insufficiently active - 1 to 500, 0.95 hazard ratio
Active (current guidelines) - 500 to 1000, 0.9 hazard ratio
Highly active - >1000, 0.95 hazard ratio
How does climate effect metabolic rates?
Warm climates
- higher RMR
- due to expending more energy in cooling processes
- and moving more outside
Cold climates
- MR can double or triple
- due to shivering
- higher BMR than warm environments
What are the inputs and outputs of energy metabolism? What can we measure?
Substrates + O2 –> CO2 +H2O + Heat
Inputs: substrates (lipids, proteins, carbohydrates, ketones) and oxygen (beginning of combustion)
Outputs: energy(heat), water, CO2 (byproducts of metabolism)
can measure oxygen and CO2 (proxies for ATP production)
occurs mainly in mitochondria (oxidative phosphorylation)
some occurs in cytoplasm (substrate level phosphorylation/glycolysis)
Outline the contents of carbohydrates, fats, proteins, and Ketones. *Substrates! (used to generate ATP)
Carbohydrates: Made of carbon, hydrogen, and oxygen (CHO). Includes sugars, starches, and fiber. Primary energy source (~4 kcal/g).
Fats: Composed of triglycerides, fatty acids, and glycerol. Provides the most energy (~9 kcal/g).
Proteins: Made of amino acids (C, H, O, N). Used for muscle repair, enzymes, and energy (~4 kcal/g).
Ketones: Byproducts of fat metabolism during low-carb intake. Used as an alternative fuel source by the brain and muscles.
Quantify the amount, energy content and distribution of each of the macronutrients within an average-sized adult.
Atwater’s factors
Carbohydrates: ~45–65% of daily intake (~4 kcal/g). Stored as glycogen (~400–500 g in muscle and liver).
Fats: ~20–35% of daily intake (~9 kcal/g). Stored as adipose tissue (~10–30% of body weight).
Proteins: ~10–35% of daily intake (~4 kcal/g). Found in muscles (~40% of body protein).
Alcohols: 7kcal/g; sugar preferred by cells; body shuts down using glucose and lipids and prefer ethanol (it is an easily accessible carbon source)
Total daily caloric needs: ~2,000–2,500 kcal/day for an average adult.
Carbohydrate distribution
Plasma glucose ~4 grams
Liver glycogen ~100 grams
Muscle glycogen ~400 grams
Total CHO stores ~500 grams
We have relatively little CHO stored in body
THEREFORE… dietary CHO is very important!
Fat distribution
Well nourished male: 80g, more for females (higher body fat percentage)
Adipose tissue triglycerides: 12,000g (108000 kcals)
Intramyocellular triglycerides (IMTG): 300g (2700 kcals)
Plasma triglycerides and plasma fatty acids: very little
Total 12,304 g
Glycogen & glycogen breakdown
Storage of CHO (in liver and muscle); 100s to 1000s of links of glucose (C6H12O6)
liver: maintains blood glucose
muscle: local fuel storage for muscle contraction
Breakdown: glycogen broken into glucose for fuel (glycogenolysis)
* glucose is major source of fuel for moderate to high intensity exercise; depletion during exercise (bonking)
What are lipids (fats)?
- Energy dense (9 kcal/gram); More than 2x as much as CHO
- Same elements as carbohydrates (C, H, O), But differ greatly in how they are linked - Typical lipid tristearin = C57H110O6
Triglyceride breakdown
Lipids as an energy source
Triglycerides must be broken down to release fatty acids for energy
- triglyceride breakdown = “lipolysis”
- lipase = enzyme that breaks down lipids/triglycerides
Protein metabolism
Proteins are constantly “turned over”; building and breaking down protein all the time
Exercise enhances protein metabolism (enhances catabolism AKA protein breakdown) and resting enhances anabolism (protein synthesis)
Important to consider nitrogen balance (growth = positive nitrogen balance; negative = aging, fasting, starving, sick)
Nitrogen balance = amount of nitrogen in urine compared to what you are eating
