Obesity and Body Mass Index Overview

Obesity Overview

• Obesity is having excess body fat.
• It differs from overweight, which is having excess weight, including from muscle, bone, or water, not just fat.
• Both refer to body weight exceeding healthy levels for height.
• A Body Mass Index (BMI) of over 30 kg/m2 is considered obese.
• A BMI between 25 and 30 kg/m2 is considered overweight.

Body Mass Index (BMI)

• BMI is weight (kg) divided by height (m) squared.
• BMI is used to screen for overweight or obesity.
• A BMI less than 18.5 is considered underweight.
• A BMI between 18.5 and 25 is considered normal.
• A BMI from 25 to 30 is considered overweight.
• A BMI of 30 or higher is considered obese.
• Obesity has classes (1, 2, and 3), depending on the BMI.

Energy Imbalance

• Obesity is often related to an energy imbalance.
• Energy In (calories consumed) must equal Energy Out (calories burned) for maintaining weight.
• If energy in exceeds energy out, the body stores excess calories as fat.
• Energy Out is used for multiple bodily functions and physical activity.

Body Fat Types

• The body has three types of fat tissue.
• White fat is the most common.
  • Found in various areas, including abdomen, thighs and buttocks.
• Brown fat produces heat when the body is cold.
  • Primarily found in infants
• Beige fat shares some characteristics with brown fat, and is found in adults.
  • Its function is more related to metabolism than heat production.

Complications of Obesity

• Obesity increases the risk of several chronic diseases. These include:
  • Insulin resistance.
  • Type 2 Diabetes.
  • Coronary artery disease.
  • Cancer (colon, rectum, prostate, gallbladder, and uterus in women).
  • Breast cancer.
  • Hypertension.
  • High cholesterol.
  • Stroke (CVA).
  • Congestive heart failure.
  • Gallstones.
  • Gout and gouty arthritis.
  • Osteoarthritis.
  • Sleep apnea.
• High obesity levels are correlated to a statistically significant decrease in life expectancy.

Causes of Obesity

• Obesity often results from a complex interplay of multiple factors.
• Overeating is a major factor in obesity. More than recommended daily calorie intake and/or a large intake of fatty foods.
• A diet high in simple carbohydrates contributes to weight gain.
• Physical inactivity reduces energy expenditure which leads to weight gain.
• Genetics play a role in the development of obesity. Several genetic conditions may lead to obesity, such as leptin deficiency.
• Psychological factors such as emotions can influence eating.
• Certain medications can lead to weight gain.
• Endocrine disorders can also play a role in the development of obesity, such as hypothyroidism or Cushing's syndrome
• Hormonal changes in women (pregnancy, menopause, etc), can lead to weight gain in women.
• Social factors, such as lack of resources, play a role. Limited access to safe places to exercise and limited access to healthy food.

Distribution of Fat

• The distribution of fat can also be a factor. Fat primarily found in abdomen/trunk is associated with greater health risks compared to fat in other regions of the body.
• Excess fat in the abdominal region can be termed visceral obesity.
• The fat distribution throughout the body may be categorized as (Android/Apple distribution in men and Pear/Gynoid distribution in women).

Cellular Characteristics of Adipose Tissue

• Adipose tissue in obese men and women has differences in cell types (hypertrophy vs hyperplasia).
• Fat tissue cell size (determined by cell density) has differences in these subtypes of obesity.

This quiz covers essential topics regarding obesity, including its definition, differentiation from being overweight, and the significance of Body Mass Index (BMI). Participants will learn about weight classifications, energy imbalance, and the health implications of obesity. Test your understanding of these important health concepts!