Obesity

Question 1

Determinants of obesity

Answer 1

1. BMI >30

2. Increased risk for CVD, hypertension, diabetes, cancer

Question 2

Body Mass Index

Answer 2

WEIGHT/HEIGHT^2
Over 30 for adults
>95% of BMI-for-age

Question 3

Forms of obesity (3)

Answer 3

1. Common obesity: increase in caloric consumption
2. Neuroendocrine obesity: hypothalmic lesions, tumors, drug interactions (Ambien)
   - glandular problem
   - very rare; associated w/ endocrine disorders
   - leads to uncontrolled appetite
3. Genetic obesity: genetic variants (est. 30-70%)
   - polymorphisms CG/GG –> CC saw increase in BMI by 2-3 points
   - mutations in leptin or leptin receptor genes

Question 4

Three components of energy expenditure

Answer 4

1. Resting metabolic rate (RMR) 60-70%
2. Thermogenic processes (10%) *NEAT
3. Physical activity (20-30%)

Question 5

Relationship between energy balance and obesity

Answer 5

1. Linear relationship btwn energy requirements and body weight (obesity can’t be explained by metabolism rates)
2. Strong link between aerobic capactiy, mitochondrial fxn, and obesity/CVD fxn
3. Brown fat: UCP
   - increases metabolic rate to generate heat
   - Correlation btwn increasing BMI and decrease in brown adipose tissue

Question 6

Homeostatic signaling system (3)

Answer 6

1. Satiety signals (short-term)
   - CCK, GLP-1 are anorexigenic
   - Grehlin is erectogenic
2. Glucostatic signals
   - insulin, glucagon, epinephrine
3. Lipostatic signals* doesn’t work ideally
   - Leptin: when concentration increases, inhibits appetite to prevent weight gain

Question 7

Adipocyte as an endocrine organ

Answer 7

Adipocyte secretes hormones that regulate metabolism of fats and sugars

2. Correlation to diabetes: some adipose-derived proteins reduce insulin sensitivity
   - leptin, adiponectin, and Visfatin increase sensitivity

Question 8

Obesity & inflammation

Answer 8

1. When BMI >30, adipose tissue gets infiltrated with macrophages and interleukins (and other inflammatory agents)
2. Secondary to weight gain

Question 9

Leptin (4)

Answer 9

1. Marker signal to brain on amount of fat tissue
2. Mutations/lack of leptin gene (ob) and receptor (db) led to obesity and diabetes
3. Accelerates maturation of female reproductive tract and onset of puberty. Surge of plasma leptin occurs in prepubertal males
   - Reverses “perceived starvation” in ob mice: DECREASED fertility, energy expenditure, immune fxn, and body temp
   - If fat secretes less leptin, body will think there is less fat and will stimulate appetite
   - If no leptin at all, even more dramatic
4. Role of maternal role on establishing set point of leptin during development (correlates later to weight gain)

Question 10

Resistin

Answer 10

1. Expressed in macrophages and adipocytes
2. Induces insulin resistance
3. High plasma levels seen in obesity

Question 11

Human adenovirus-36

Answer 11

1. Associated with increased body weight and reduction of serum lipids (lower cholesterol and TAG)
2. Those with antibody against virus had an increase in 5-6 BMI points
3. Thought to be due to E4orf1 gene: infects nucleus or host, turns on lipogenic eznymes to increase TAG storage and differentiation of new adipocytes
4. Also a hypothesis that adenovirus decreases leptin levels

Question 12

Healthy obese

Answer 12

1. Individuals with BMI>30 but whom have no cardiometabolic abnormalities.
2. Suggests obesity can be a risk factor not a disease