Obesity: An expanding epidemic
[Slide 23]
I. Birth of an epidemic [slides1-22 auto-animation 2 second transition]
A. Last 20 years [1]
B. Spread across country
1. from < 15% in 1985 [slide 1]
2. to > 25% in 2006 [slide 22]
II. Introduction [slide 24]
A. Obesity
1. Major public health issue
2. Has physical, environmental, and genetic influences
B. Is
1. Related to consumption
2. Result from high caloric intake
C. This lecture reviews the following [slide 25]
1. Definition and epidemiology
2. Comorbid illness
3. Mechanism of disease
4. Treatment
III. Obesity
A. Defined [slide 26]
1. Measured through the body mass index (BMI)
2. BMI defined as weight in kilograms / height in meters squared
3. Normal weight - BMI 18.5-24.9
4. Overweight - BMI 25.0-29.9
5. Obesity - BMI ≥ 30.0 [2]
a. Class I BMI 30.0-34.9
b. Class II BMI 35.0-39.9
c. Class III (extreme) BMI ≥ 40.0
B. Obesity epidemiology [3] [slide 27]
1.
66%
a. 32% obese
b. 5% extreme obesity
2. Mexican American 76% overweight or obese
3. Non-Hispanic Black 76%
4. Non-Hispanic White 64%
5. non-Hispanic white women 36%
6. Mexican American women 50%
7. Non-Hispanic black women 65%
C. We now move from [slide 28]
1. Definition and epidemiology to
2. Comorbid illness
D. Obesity morbidity and mortality [slide 29]
1. 300,000 obesity-related deaths in US per year [4]
2. 5x ↑ risk for diabetes [5]
3. 5x ↑ risk for gallbladder disease [5]
4. Mood disorders (depression and bipolar) 18% in non-obese v. 22% in obese [6]
5. Obese ↑ hospitalization and death from cardiovascular disease[7]
E. We now move from [slide 30]
1. Comorbid illness to
2. Mechanism of obesity
F. Mechanisms of obesity
1. Environment [slide 31]
a. Types of food available and portion sizes
i. ~3,500 calories = 1 pound weight gain
ii. When caloric intake > energy expenditure weight ↑
iii. Increased intake due to increased portion size
b. Sedentary lifestyle
i. Decreased activity (e.g., couch-potato)
ii. Decreased mobility (e.g., disability)
2. Genetics comprise 50% of risk for obesity[8;9] [slide 32]
a. Obesity runs in families
i. 75% monozygotic v 60% dizygotic twins
ii. Body weight of adoptees relate to biological more than adoptive parents
b. Specific human gene mutations have been identified
i. Leptin
i. Picture child with leptin deficiency
ii. Picture after leptin replacement
ii. Proopiomelanocortin (POMC)
c. Obesity can be bred in or out of mice
3. Many feedback pathways involved [slide 33]
a. Adipocytes, or fat cells, produce the hormone leptin
i. ↓ feeding by acting in arcuate nuc. of hypothalamus
ii. ↑ expenditure by acting in the brain and muscles
b. Stomach produces the hormone ghrelin
i. ↑ feeding by acting in arcuate nuc. and vagus nerve
ii. ↓ energy expenditure by acting in brain and adipocytes
c. Both leptin and ghrelin modulate brain activity related to emotion and behavior (e.g., in the hypothalamus/amygdala)
d. Feeding modulates/is modulated by neuropathways[10]
i. ↑ Dopamine when liked food presented and eaten
ii. ↑ Endogenous opioids ↑ feeding
iii. ↓ in glutamate will initiate feeding
iv. ↑ GABA will ↑ feeding
v. ↑ Serotonin ↓ feeding
G. Stress eating and opioids [slide 34]
1. Stress increases sugar intake [11]
2. Opiates increase sugar intake [12]
3. Common link: proopiomelanocortin which is precursor for
a. Endogenous opioid beta-endorphin
b. Stress hormone adrenocorticotropin (ACTH)
c. Feeding hormone alpha-melanocyte-stimulating hormone (alpha-MSH)
H. Control of feeding [slide 35]
1. Emotion
a. Stress
b. Boredom
2. Environment
a. Portion size
b. Availability
3. Intrinsic
a. Hormonal regulation
b. Dopamine
I. Dopamine and reward [slide 36] [13]
1. Pleasurable things increase dopamine
a. Drugs
b. Sex
c. Food
2. Prolonged exposure decreases dopamine
a. Drugs
b. Food
J. BMI and dopamine receptor [slide 37] [14]
1. Non-obese no relation between D2 and BMI
2. Obese D2 and BMI inverse correlation
K. Dopamine and reward [slide 37]
1. Early exposure
a. Increased dopamine release
b. Increased dopamine receptors (esp. D2)
2. Prolonged exposure
a. Decreased dopamine release
b. Down regulation of receptors
c. Seen with PET imaging in obesity
L. Liking versus craving? [slide 38]
1. Increased motivational activity when hungry [15]
a. Caused by stress
b. Caused by food deprivation
2. Desire is for sweets
M. What about carbohydrates? [slide 39]
1. They increase