148. Obesity Pathophysiology

Question 1

What is obesity?
What is anthropometry?
What is BMI?
How do women and men differ at same BMI?

Answer 1

Obesity: abnormal/excessive fat accumulation that poses risk to health
Anthropometry: science of measuring human body (skin fold thickness/circumference, bioelectrical impedance, dual-energy xray absorptiometry, air displacement plethysmography, CT scan)
BMI: may not accurately indicate %body fat, but practical and useful determinant of excess body fat and risk of morbidity/mortality
Women higher body fat % than men at same BMI

Question 2

Lipotoxicity

• how does adipose tissue affect the body
• how do you measure lipotoxicity?
• what is metabolic syndrome?
• what are the complications?
• why is liposuction not helpful?

Answer 2

Toxic effects of excess fat (secretory endocrine organ)
Waist Circumference correlates to Visceral Adipose Tissue (more dangerous than SubQ fat)
VAT: less insulin action, more secreted adipokines (dyslipidemia, dysfunction, inflammation, insulin resistance)
Secreted adipokines: TNF alpha, IL6, EGF, Leptin
Adiponectin (less signaling in increased WC = causing insulin sensitivity)
Abnormal weight gain: more adipocytes w/o enough angiogenesis = hypoxia = inflammation and fibrosis

Liposuction: removes subQ fat not VAT

Metabolic Syndrome: 3 of: high WC (not BMI), high TGs, low HDL, high BP, high fasting glucose

Central obesity = insulin resistance = atherosclerosis (inflammation, dyslipidemia, HTN)

Goal of weight loss = decrease visceral adipose tissue

Question 3

What are the effects of obesity on the body?

Answer 3

1. Increased mechanical burden (higher back pain, SoB with activity, kids with varus deformity in knees)
2. Increased abd pressure (increased GERD, less diaphragm movement = less FRC/ERV/RV)
3. Increased resp burden: high metabolism = high Vo2 Vco2, low chest compliance due to weight on chest, low FRC/ERV due to increased abd pressure, V/Q mismatch (lower lungs squished), OSA, high PaCO2, OHS (obesity hypoventilation syndrome - retained CO2), Cor Pulmonale
   Pickwickian Syndrome: OSA and OHS
4. CV Burden: high metabolism and edema = high blood volume = high CO = high LVEDV/wall stress = Eccentric LVH (chamber dilation + wall thickening) = HTN = Concentric LVH (more wall thickenss) = CHF
5. Increased risk of peripheral venous stasis = ulceration and PE
6. Effects of poor diet and low physical activity

Question 4

How does obesity affect COVID infection and outcomes?

Answer 4

Obesity is risk factor for covid complications (chronic disease altering acute disease)

• mechanistic changes: metabolic dysfx, immune impairments, adipose inflammation
• physical changes: pulm dysfx, OSA, high VAT
• comorbidities: HTN, CVD, DMII, hyperlipidemia, kidney/liver disease

Worse COVID outcomes due to interactions b/w obesity, chronic disease, and social determinants of health