Energy and Fat Balance

Question 1

What is the percentage cost from DIT of the macronutrients?

Answer 1

• 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

Question 2

What is the problem of quantifying protein DIT?

Answer 2

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

Question 3

What impact does high fat diet have on DIT?

Answer 3

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.

Question 4

What are the components of energy expenditure?

Answer 4

• Physical Activity
• DIT
• Adaptive Thermogenesis?
• Resting Metabolic Rate

Question 5

What is Adapative Thermogenesis?

Answer 5

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.

Question 6

What is Fat Balance?

Answer 6

Fat Intake - Fat Oxidation (+ Fat Synthesis)

Question 7

Explain the concept of the ‘unregulated zone’, as outlined by James Hill et al 2012

Answer 7

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.

Question 8

What are the problem of existing in chronically very high or very low energy expenditure?

Answer 8

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

Question 9

What is the typical relationship between fat balance and energy?balance? Give evidence

Answer 9

-If you are in energy balance you are most likely in fat balance. Schrauwen et al 1998

Question 10

In a typical mixed diet, how much of your total energy ingested is burned in DIT?

Answer 10

8-10%

Question 11

What is the energy content of Fat Tissue, Fatty Acids, and body fat cells, respectively?

Answer 11

• 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

Question 12

How much brown fat do adult humans have on average?

Answer 12

about 10-15 grams around the scapula

Question 13

Explain the novel hypothesis of carb availability as a regulator of energy balance with exercise, and who proposed it?

Answer 13

• 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

Question 14

How may training status impact the magnitude of post exercise hunger?

Answer 14

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)

Question 15

What explains differences between gross energy of food and metabolically available energy of digested food?

Answer 15

• 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)

Question 16

What is a potential relationship between Physical activity energy expenditure and DIT?

Answer 16

More physical activity will mean more energy intake which means more DIT

Question 17

What is the gross calorie content of different macronutrients as whole food? (not what is available from digestion)

Answer 17

• 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

Question 18

What is the average net energy yield of macronutrients?

Answer 18

• Carbs: 3.4 cal per gram
• Fat: 8.4 cal per gram
• Protein: 3.2 cal per gram
• Alcohol: 6.0 cal per gram

Question 19

What is the average metabolically available energy yield from systemic metabolites of digested macronutrients?

Answer 19

Carbs: 3.7 cal per gram
Fat: 8.9 cal per gram
Protein: 4.1 cal per gram
Alcohol: 7.1 cal per gram

Question 20

What explains the difference between metabolically available energy yield and net energy yield in oxidation?

Answer 20

-Diet Induced thermogenesis

Question 21

What explains the difference between metabolically available energy and stored energy?

Answer 21

• 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

Question 22

What are the different respiratory quotients of Amino acids, sugars and fatty acids?

Answer 22

• AA: 0.8
• Sugar: 1
• NEFA: 0.7

Question 23

Metabolites can be readily converted, what is the exception to this rule?

Answer 23

-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.

Question 24

What are the enzymes that cause De Novo Lipogenesis?

Answer 24

• Acetyl CoA Synthatase

- Fatty Acid Synthatase

Question 25

What is the relationship between carbohydrate intake and substrate oxidation?

Answer 25

-Carbohydrate ingestion stimulates its own metabolism. Increases in blood glucose increases glucose oxidation

Question 26

What is the relationship between carbohydrate balance and fat oxidation?

Answer 26

Inverse. As carb balance increases, fat oxidation decreases. The lower the carbohydrate balance, the higher the fat oxidation

Question 27

What is required for carbohydrates to be converted to fats (De Novo Lipogenesis) under normal circumstances?

Answer 27

-Carbohydrate stores need to be saturated, which would require an unreasonable amount of carb intake every day exceeding that of your TDEE

Question 28

What is the primary site for fat synthesis in the body in response carbohydrate overfeeding? Give reference

Answer 28

Aarsland et al 1997:

3g of 170g of excess fat stored in the body came from the liver DNL, the rest is done by adipose tissue

Question 29

How much energy intake comes from ethanol in the UK, on average?

Answer 29

4.9%, or 8.4% if exclusing alcohol non-consumers from the data

Question 30

What impact does alcohol have on appetite? Give reference

Answer 30

Increases appetite, and thus fat intake/energy intake (Westerterp et al 1999)

Question 31

What impact does alcohol intake have on lipid handling? Give reference

Answer 31

-Increases synthesis, and decreases oxidation
Siler et al 1999 found that NEFA appearance and fat oxidation are both significantly lower after ethanol consumption
- Fractional DNL 25-30% higher 3-4 hours after alcohol intake, but only 3-4% of the total alcohol converted into fat.

Question 32

What are the two pathways of alcohol metabolism and their respective efficiencies?

Answer 32

• Alcohol Dehydrogenase (12% DIT)

- Microsomal Ethanol Oxidising System (27% DIT)

Question 33

How can changes in physical activity change the magnitude of all of the components of energy expenditure?

Answer 33

• Increase PA can cause compensatory decrease in PA at other times
• Increase in PA can lead to increased eating to create energy balance, increasing DIT

Question 34

How can changes in energy intake affect changes in energy expenditure?

Answer 34

• Long term decrease in weight due to deficit can decrease RMR due to less metabolically active tissue in a smaller body
• Rapid weight loss can reduce RMR/DIT as a protective mechanism via regulating adaptive thermogenesis (but not much in humans)

Question 35

How can changes in macronutrient breakdown of energy intake impact energy expenditure?

Answer 35

-Different macronutrients have diffrent DIT. High fat diets will have lower DIT than high protein diets.

Question 36

What did Hall et al 2015 show about the interaction of decreasing energy intake on energy expenditure?

Answer 36

-Decreasing intake led to a subsequent decrease in expenditure

Question 37

When is the body best adapted to staying in energy balance? Give evidence

Answer 37

Jean Mayer et al 1956 found that energy balance is best regulated at high, but not excessively high energy flux/level of physical activity.. Energy intake is better matched to expenditure among physically active people than sedentary people. (Supported by unregulated zone theory by james hill)

Question 38

What is the difference between carbohydrate and fat overfeeding in humans? give reference

Answer 38

Horton et al 1995 found that overfeeding fat and carbs, both 50% above energy requirements, resulted in 90-95% and 75-85% storage of excess energy, respectively, meaning that overfeeding carbohydrate leads to less fat accumulation than fat overfeeding.

Question 39

What evidence exists to suggest that compensatory regulation of energy expenditure occurs in response to underfeeding?

Answer 39

-Heyman et al 1992 found that changes to energy expenditure (alterations in PA, RMR and DIT) offset 37% of the decrease in energy intake