Obesity and its Causes

5 Questions

What are the key hormones involved in energy balance and appetite regulation?

Insulin

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?

triggering appetite reduction and shifting to 'Spend Energy' mode

Match the obesity type with its characteristics:

Apple Type = Central or abdominal adiposity, increased waist circumference, higher morbidity risk Pear Type = Typical female distribution of fat, less health risks

Ghrelin rises just after meals.

False

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