Lecture 36: Coordinating metabolism - Obesity

Question 1

How do we calculate obesity using BMI (what is the equation) and what number is considered obese?

Answer 1

BMI = Weight (kg) / (Height (m))2

• BMI > 30 = obese

Question 2

Describe some of the health consequences of obesity.

Answer 2

Obesity can lead to increased risk of type 2 diabetes, heart disease, stroke, impaired reproduction, liver and gall bladder disease, respiratory disorders and certain cancers.

Question 3

Explain the energy balance model of obesity

Answer 3

E(intake) = E(expended) + E(stored)
E(expended) = basal metabolism + activities
E(stored) = weight gain

When energy intake is greater than energy expenditure (i.e. a positive energy balance exists) the extra energy is stored (as fat).

Question 4

Discuss the reducing energy intake strategy for the treatment of obesity related to the energy balance model:

Answer 4

Weight loss can be achieved by:

Reducing energy intake
Calorie restriction, low fat diet, low carb diet, blocking
fat absorption (Xenical).

Reality:
Weight loss can be achieved but these diets can be
difficult to maintain.
Furthermore, the body resets to a lower basal
metabolism which makes it hard to maintain the
weight loss

Question 5

How can a keto diet help weight loss?

Answer 5

• Diets restricted in carbohydrates.
• Promote the use of body fat and ketosis.
• Reduces insulin secretion.
• Reduces appetite from satiety effect of protein.
• There are some concerns around removing healthy carbs i.e. pulses and grain and some fruits.
• Keto diet based on saturated fats increase LDL levels.

However:
* Data shows no more effective than low fat diets at promoting weight loss

Question 6

Can weight loss be achieved via exercise?

Answer 6

Yes

• Increasing muscle mass because muscle is more metabolically active than fat and burns more ATP at rest.

Question 7

How do the hormones leptin, GLP-1 and Ghrelin effect appetite?

Answer 7

Leptin from adipose signals to reduce appetite.

GLP-1 from the gut also signals to reduce appetite.

Meanwhile, ghrelin from the stomach signals that the gut is empty and stimulates appetite

Question 8

What are the differences between the energy balance model and the Carbohydrate-insulin model?

Answer 8

Energy balance model:
Increased intake of energy dense food promotes fat storage
- food first then stored

Carbohydrate-insulin model:
High carb diets promote high insulin which promotes storage which further promotes hunger
- storage first, need more and more food

Question 9

Other than exercise how else can we increase basal metabolism?

Answer 9

• Uncouplers i.e. substances that uncouple OxPhos in the mitochondria, causing energy to be released as heat rather than generating ATP

Dangerous and could lead to death but some progress is being made in this field