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Questions and Answers
What are the key hormones involved in energy balance and appetite regulation?
What are the key hormones involved in energy balance and appetite regulation?
- Insulin (correct)
- Leptin (correct)
- Peptide YY3-36 (correct)
- Ghrelin (correct)
Obesity is not just a matter of what weight is currently fashionable or socially acceptable, it is a ____________.
Obesity is not just a matter of what weight is currently fashionable or socially acceptable, it is a ____________.
disease
What is the role of leptin in the hypothalamic-leptin axis?
What is the role of leptin in the hypothalamic-leptin axis?
triggering appetite reduction and shifting to 'Spend Energy' mode
Match the obesity type with its characteristics:
Match the obesity type with its characteristics:
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Ghrelin rises just after meals.
Ghrelin rises just after meals.
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Study Notes
Physiology of Obesity
- Obesity is a complex, multifactorial condition involving genetic, environmental, and social factors
- Appetite and satiety are regulated by multiple humoral and neurological mechanisms, integrated in the hypothalamus
- Hormones involved in energy balance and appetite regulation include leptin, insulin, ghrelin, and peptide YY3-36
Causes of Obesity
- Genetic predisposition
- Disruption in energy balance
- Environmental and social factors
Models of Obesity Pathology
- Overeating and inactivity are simplistic views of obesity
- Various pathways lead to obesity, with complex interactions between factors
The Hypothalamic-Leptin Axis
- Leptin is produced in fat cells and triggers receptors in the hypothalamus
- This activates the "Spend Energy" mode, reducing appetite and increasing energy expenditure
- In the "Conserve Energy" mode, appetite increases, and metabolic rate decreases
Leptin Resistance
- Leptin receptors can be blocked, tricking the hypothalamus into thinking there is no leptin
- This leads to increased appetite, slowed metabolic rate, and increased fat storage
- Orexin-A stimulates hunger and wakefulness, contributing to obesity
Obesity Types
- Apple (android) type: central obesity, associated with higher morbidity risk
- Pear (gynoid) type: peripheral fat distribution, fewer health risks
Body Mass Index (BMI)
- Calculated by weight (kg) / height (m)² or weight (lbs) x 705 / height (in)²
Waist to Hip Circumferences
- Android: central fat distribution, increased waist circumference and WHR, associated with higher morbidity risk
- Gynaecoid: peripheral fat distribution, fewer health risks
Visceral Obesity and the Insulin Resistance Syndrome
- Characterized by central obesity, glucose intolerance, hypertension, atherosclerosis, and polycystic ovary syndrome
Measurement of Body Fat
- Skin fold thickness (skin pinch) measures subcutaneous fat
- Bioelectrical impedance analysis (BIA) estimates body composition
The Insulin Resistance Syndrome
- Clinical manifestations include central obesity, glucose intolerance, hypertension, atherosclerosis, and polycystic ovary syndrome
- Biochemical abnormalities include hyperinsulinemia, high TG, low HDL-C, and small, dense LDL particles
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