Obesity Overview and Energy Imbalance

Obesity Overview

• 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 Imbalance

• 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.

Body Fat Types

• The body has three types of fat tissue: white, brown, and beige.
• White fat: stores energy, makes hormones, and can lead to complications.
• Brown fat: releases energy as heat (in infants and adults)
• Beige fat: produces heat using carbohydrates and fats.

Obesity Complications

• 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

Causes of Obesity

• 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.

Regional Fat Distribution

• 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.