Lecture 4 Energy Balance and Control

Question 1

What is energy balance?

Answer 1

Maintenane of energy stores

Question 2

How does the brain regulate our energy stores?

Answer 2

The accuracy of the system is >99% but the brain does want you to defer to a positive balance, and it will send signals to try and promote this. Caveat is that you still have to make the choice of what you eat.

Question 3

How much do people gain on average per year?

Answer 3

+ 1.8 lbs/ yr

Question 4

How do changes in energy cause changes in body composition?

Answer 4

EI (metabolizable energy) - EE (Heat: BEE+TEF+EEPA)

These must be equivalent to be weight stable

Question 5

What macronutrient storage do our bodies rely on?

Answer 5

1. Glucose
2. Glycogen
3. Protein
4. TAGs

Question 6

Why are changes to body energy (weight) due to imbalances NOT linear?

Answer 6

The time taken to extract energy from the different stores differ with glucose only bieng seconds and fats could take a long time. The bodies response to imbalances is slow.

Question 7

Why does it take longer to get energy out of adipose tissue?

Answer 7

• The brain defends it
• not lipid soluble
• Also would be mobilizing all the other storage compartments

Question 8

Factors contributing to body changes due to energy imbalances

Answer 8

• composition of tissue mass lost or gained, imapct on energy expenditure (muscle vs. fat) and intake (type of fuel)

Question 9

What type of energy is food?

Answer 9

potential energy in which nutrients must be oxidized.

Question 10

What is the premise of nutrient balance?

Answer 10

When in energy balance, CHO and protein are not converted to fat, thus
* energy balance = macronutrient balance
* intake = bodies rate of oxidation of each macronutrient

ingestion in excess of oxidation = energy stored as fat

Question 11

What is the hierarchy of oxidation?

Answer 11

alcohol > protein > carbohydrate > fat
Based on: 1. storage capacity 2. energy cost of conversion 3. specific fuel needs of tissues

Question 12

What are the energy stores?

Answer 12

alcohol: none, toxic so body removes
protein: non, N is toxic so excreted in urine
CHO: 24hr glycogen storage, excess stored as fat
Fat: efficent storage but not readily ozidized

Question 13

Why is fat excellent fuel storage?

Answer 13

• Fat has double the energy relative to protein or CHO
• Adipose is more dense than lean tissue being made up of 85% lipid and very little water whereas lean tissue is 20% protein and has more water.
• proteins has less fuel because the N needs to be excreted

Question 14

What is the most efficient utilization of nutrients for energy production?

Answer 14

stored nutrients are more efficient than ingested nutrients. The brain and body work together to release fuel stores and has a preference for what you eat and where it is stored.

Question 15

Macromolecule turnover

Answer 15

Fat molecule lasts aout 1 year before it is turned over and CHO and glycogen are used immediately

Question 16

What is the body weight ‘set-point’?

Answer 16

states that our bodies have a preset weight baseline hardwired into our DNA. According to this theory, our weight and how much it changes from that set point might be limited. The theory says some of us have higher weight set points than others and our bodies fight to stay within these ranges such that increases or decreases in body weight via energy imbalances quickly reset.

asymmetrical towards gain

Question 17

What controls the body weight ‘set-point’?

Answer 17

The CNS
* ventromedial hypothalamus (satiety centre)
* lateral hypothalamus (feeding centre)

Question 18

What is the settling point?

Answer 18

Adaptation of the brain/ body to adapt and accept ‘set-point’ changes during a life cycle.

Extreme weight loss diets brain resets but can overshoot

Question 19

What may be contributing to increasing set-points?

Answer 19

• Evolutionary bias for defending energy stores & weight gain
• availability of food
• sedentary lifestyle

Question 20

How does the brain respond to food on a daily basis?

Answer 20

The brain adapts to what you feed it, and it is always trying to catch up. It takes a while for it to process what you ate the previous day and so it changes your perception the following day to regulate what you eat.

This is perception it tells you nothing of your stores.

Question 21

What is the average caloric intake?

Answer 21

1,500-3,000 kcal/day