Obesity Overview and Energy Imbalance

Study Notes

Obesity is defined as having too much body fat.
Overweight is defined as a BMI from 25 to 30 kg/m2
Obesity is defined as a BMI greater than 30 kg/m2.
BMI (Body Mass Index) is a screening tool for overweight or obesity.
BMI = weight (kg) / height (m)^2
BMI < 18.5 = underweight
BMI 18.5 - 25 = normal
BMI 25-30= overweight
BMI > 30 = obese
Obesity is further categorized by class:
- Class 1: BMI 30 - < 35
- Class 2: BMI 35 - < 40
- Class 3: BMI 40 or higher

Energy imbalances cause overweight and obesity.
Energy IN = calories from food and drinks.
Energy OUT = calories used for breathing, digesting, physical activity, temperature regulation.
Weight gain occurs when energy IN is greater than energy OUT.
Weight loss occurs when energy OUT is greater than energy IN.

Cosmetic problems
112,000 deaths per year in the US directly related to obesity, most in patients with a BMI > 30.
Life expectancy significantly reduced for those with a BMI > 40.
Obesity increases the risk of chronic diseases:
- Insulin resistance
- Type 2 diabetes mellitus
- Coronary artery disease
- Cancer (colon, rectum, prostate, gallbladder, uterus, breast)
- Hypertension
- High cholesterol
- Stroke
- Congestive heart failure
- Gallstones
- Gout and gouty arthritis
- Osteoarthritis
- Sleep apnea

Energy imbalance: Consuming more calories than burning.
Genetic factors: Genes affect body fat storage, distribution, energy conversion, and exercise efficiency. Leutin deficiency can lead to obesity.
Overeating: High calorie intake without sufficient caloric expenditure. High density foods (fat and sugar) contribute to overeating and gain weight.
Diet high in simple carbohydrates: Quickly absorbed, leading to high insulin release and fat tissue growth.
Frequency of eating: Frequent small meals associated with steadier insulin levels than infrequent large meals.
Physical inactivity: Less calorie expenditure.
Medications: Some antidepressants, anticonvulsants, some diabetes medications, oral contraceptives, and corticosteroids.
Psychological factors: Emotional eating (boredom, sadness...).
Endocrine disorders: Hypothyroidism, Cushing's syndrome; hormonal imbalances, which reduce energy expenditure.

Body shape and regional fat distribution (location of fat) are more important for health than total body fat.
Visceral fat (fat around internal organs) is most dangerous; poses greater health risks than subcutaneous/peripheral fat (fat just beneath the skin)
Different kinds of obesity: Android (apple shape--upper body fat; visceral fat) and Gynoid (pear shape--lower body); differences in fat cell function.