Energy and Fat Balance Flashcards
What is the percentage cost from DIT of the macronutrients?
- Carbs cost 8-12% of overall calories ingested
- Fat costs 0-3%
- Protein costs 21% ON AVERAGE
- Alcohol is either 12-15% or 27% dependent on the pathway
What is the problem of quantifying protein DIT?
The chemical structure of two proteins can be more different from each other than any protein is from a carb, so the cost of breaking down will be highly variable
What impact does high fat diet have on DIT?
It may cause individuals to have lower DIT overall, not just due to the higher fat content of the meal having a lower DIT itself.
What are the components of energy expenditure?
- Physical Activity
- DIT
- Adaptive Thermogenesis?
- Resting Metabolic Rate
What is Adapative Thermogenesis?
Unnecessary and purposely inefficient metabolism for the purpose of producing heat, associated with brown adipose tissue. Can be up or down regulated in very small amounts in humans.
What is Fat Balance?
Fat Intake - Fat Oxidation (+ Fat Synthesis)
Explain the concept of the ‘unregulated zone’, as outlined by James Hill et al 2012
There is a threshold for physical activity that lends itself to optimal weight regulation, and a linear relationship between energy intake and expenditure. Below that level, there is a counterintuitive relationship between inactivity and energy intake, leading you to eat an inappropriate amount of food for your energy requirements.
What are the problem of existing in chronically very high or very low energy expenditure?
Its very hard to naturally eat enough to balance it at an extremely high expenditure, and its easy to accidentally overeat at a very low energy expenditure
What is the typical relationship between fat balance and energy?balance? Give evidence
-If you are in energy balance you are most likely in fat balance. Schrauwen et al 1998
In a typical mixed diet, how much of your total energy ingested is burned in DIT?
8-10%
What is the energy content of Fat Tissue, Fatty Acids, and body fat cells, respectively?
- 8 calories per gram of TAG in Fat tissue
- 9 cal per gram in Fatty Acids
- 7.1 cal per gram in Body fat Cells due to the stuff in the cell that isnt fat
How much brown fat do adult humans have on average?
about 10-15 grams around the scapula
Explain the novel hypothesis of carb availability as a regulator of energy balance with exercise, and who proposed it?
- Leptin is lowered in response to decreased carb availability after exercise (due to muscle glycogen oxidation)
- Reduces hepatic glycogen stores which can induce hunger via vagal nerve stimulation
- Gonzalez, Betts and Thompson 2019
How may training status impact the magnitude of post exercise hunger?
Trained individuals have improved fat oxidation, so rely less on endogenous carb, so less carb is used meaning less leptin suppression, so less hunger and less likelihood of post exercise dietary compensation (Gonzalez, Betts and Thompson 2019)
What explains differences between gross energy of food and metabolically available energy of digested food?
- Fecal Loss (1% of carb lost and 5% of fat lost)
- Urine Loss (20% of gross protein energy lost, due to nitrogen lost as urea)
What is a potential relationship between Physical activity energy expenditure and DIT?
More physical activity will mean more energy intake which means more DIT
What is the gross calorie content of different macronutrients as whole food? (not what is available from digestion)
- Carbs: 3.7-4.1 cal per gram
- Fat: 9.4 cal per gram
- Protein: 5.6 cal per gram
- Alc: 7.1 cal per gram
What is the average net energy yield of macronutrients?
- Carbs: 3.4 cal per gram
- Fat: 8.4 cal per gram
- Protein: 3.2 cal per gram
- Alcohol: 6.0 cal per gram
What is the average metabolically available energy yield from systemic metabolites of digested macronutrients?
Carbs: 3.7 cal per gram
Fat: 8.9 cal per gram
Protein: 4.1 cal per gram
Alcohol: 7.1 cal per gram
What explains the difference between metabolically available energy yield and net energy yield in oxidation?
-Diet Induced thermogenesis
What explains the difference between metabolically available energy and stored energy?
- Alcohol is not stored in the body
- Fat is 100% converted, so no difference
- Carbs is 95% efficient due to need for ATP investment
- Protein is about 75% efficient. Requires about 1 calorie to store a gram of protein
What are the different respiratory quotients of Amino acids, sugars and fatty acids?
- AA: 0.8
- Sugar: 1
- NEFA: 0.7
Metabolites can be readily converted, what is the exception to this rule?
-Protein and carbs can be converted. Either can be converted to fat. But Fat cannot really be converted back into carbs or protein by humans.
What are the enzymes that cause De Novo Lipogenesis?
- Acetyl CoA Synthatase
- Fatty Acid Synthatase
