Obesity Flashcards
(14 cards)
Obesity definition
Definition
• BMI (Body Mass Index):
• Normal: 18.5–24.9
• Overweight: 25–29.9
• Obese: ≥30
• Class I: 30–34.9
• Class II: 35–39.9
• Class III (Morbid): ≥40
Tip: You may be asked to calculate or interpret BMI. Memorize the formula:
BMI = weight (kg) / height (m²)
Obesity pathophysiology
Pathophysiology
• Increased leptin (produced by adipose tissue) – but leptin resistance develops.
• Insulin resistance: Obesity is a major driver.
• Chronic low-grade inflammation due to adipokine secretion.
Tip: Despite increased fat stores, leptin doesn’t reduce appetite in obesity due to leptin resistance—a commonly tested concept.
Obesity: endocrine association
Type 2 Diabetes Mellitus – insulin resistance hallmark.
• Polycystic Ovary Syndrome (PCOS) – associated with obesity and insulin resistance.
• Non-alcoholic fatty liver disease (NAFLD) – can progress to steatohepatitis and cirrhosis.
Obesity: cardiovascular
Hypertension, dyslipidemia, and coronary artery disease.
• Obstructive sleep apnea – strongly linked to obesity; commonly tested.
Type 2 Diabetes Mellitus (T2DM)
Pathophysiology:
• Obesity → ↑ Free fatty acids, TNF-α, resistin → Insulin resistance
• Adipose tissue → ↑ leptin, but with leptin resistance
• Clinical links: Acanthosis nigricans, hyperinsulinemia, metabolic syndrome
Tip: Look for obese patients with polyuria, polydipsia, fatigue. Glucose tolerance testing may be described
Metabolic Syndrome
Defined by ≥3 of:
• Waist circumference ↑ (central obesity)
• Hypertriglyceridemia
• Low HDL
• Hypertension
• Hyperglycemia
• Pathogenesis: Insulin resistance + visceral fat accumulation
Tip: Often a prelude to CAD and T2DM. Think of it as “pre-diabetes + pre-CVD.”
Non-Alcoholic Fatty Liver Disease (NAFLD)
Spectrum: Steatosis → Non-alcoholic steatohepatitis (NASH) → Fibrosis → Cirrhosis
• Associated with: Obesity, insulin resistance, metabolic syndrome
• Labs: Elevated ALT > AST (opposite of alcoholic hepatitis)
Tip: Liver biopsy shows macrovesicular steatosis; ALT usually mild to moderately elevated.
Obstructive Sleep Apnea (OSA)
Strongly associated with obesity
• Mechanism: Pharyngeal soft tissue collapse during sleep → intermittent hypoxia → ↑ sympathetic tone → hypertension
• Symptoms: Daytime sleepiness, loud snoring, fatigue
Tip: OSA increases the risk of pulmonary hypertension and right-sided heart failure.
Obesity Hypoventilation Syndrome (Pickwickian Syndrome)
Mechanism: Blunted ventilatory response to CO₂ due to obesity
• Features: Hypoventilation, ↑ PaCO₂, ↓ PaO₂
• May co-occur with OSA
Tip: Look for daytime hypercapnia + obesity. Rule out other causes of hypoventilation.
Cardiovascular Disease
Mechanisms:
• Obesity → ↑ LDL, ↑ triglycerides, ↓ HDL
• Inflammation (IL-6, TNF-α) → atherogenesis
• Endothelial dysfunction → HTN, CAD
• Diseases: Atherosclerosis, MI, stroke, heart failure, HTN
Tip: Obesity increases both macrovascular (MI, stroke) and microvascular (retinopathy, nephropathy) risks via insulin resistance.
Osteoarthritis
Mechanism: Mechanical wear-and-tear, especially in knees and hips
• Finding: Joint space narrowing, osteophytes, subchondral sclerosis
Tip: Joint pain worsens with use (unlike RA); often a chronic comorbidity in obese patients.
Cancers
Obesity increases risk for hormone-sensitive and GI tract cancers:
• Breast (postmenopausal) – ↑ peripheral estrogen via aromatization in fat
• Endometrial – unopposed estrogen
• Colorectal – chronic inflammation
• Esophageal adenocarcinoma – GERD-related
Tip: On Step 1, obesity-related cancer risks may be tested via estrogen or insulin pathway mechanisms.
Polycystic Ovary syndrome (PCOS)
Associated with obesity + insulin resistance
• Features: Oligomenorrhea, hirsutism, acne, infertility
• Labs: ↑ LH:FSH ratio, ↑ androgens, insulin resistance
Tip: Treatment includes weight loss and metformin to restore ovulation.
GERD
Mechanism: ↑ intra-abdominal pressure → lower esophageal sphincter incompetence
• Complications: Barrett esophagus → adenocarcinoma
Tip: Obesity and hiatal hernia often coexist in GERD patients.
