Obesity I: Introduction to Concepts

Obesity I: Introduction

• Aim of the lecture:
  • Define obesity.
  • Explain how obesity is measured.
  • Describe prevalence in different populations (US, worldwide, Australia, NSW).
  • Examine the relationship between obesity and ethnicity, age, and socioeconomic status.
  • Analyze the medical and financial impact of obesity on individuals and society.

What is Obesity?

• Body utilizes fat cells for long-term energy storage.
• Two types of fat cells:
  • Brown fat cells (BAT): Generate heat, located beside spinal column.
  • White fat cells: Insulate body, cushions organs, stores energy long-term. Each white fat cell is 85% fat stored in a vacuole.

White Fat Cells

• Multiple functions: insulation, cushioning, energy storage.
• White fat cells are distributed differently in men and women (men - waist, women - hips/thighs).
• Amount of fat is a measure of energy storage.
• Important endocrine functions:
  • Leptin
  • Resistin
  • Fasting-inducing Adipose Factor (akin to Leptin)

Measurement of Obesity

• Estimate body fat percentage to measure obesity.
• Body Mass Index (BMI) is a common measure.
• Calculate BMI by dividing weight in kilograms by the square of height in meters.
• Example: 85 kg / (1.79 m x 1.79 m) = 26.6 BMI.

BMI for Adults

• BMI categories: underweight, normal, overweight, obese (moderate, severe, very severe).
• The WHO classification scheme defines BMI ranges.

Pros and Cons of BMI

• Pros:
  • Easy to use.
  • Can be measured remotely.
  • Accurate.
  • Correlates with adiposity.
• Cons:
  • Ignores fat distribution.
  • Ignores muscle mass.
  • Influenced by age and/or trunk-to-leg length.

Other Measures

• Skin fold thickness (calipers): Measures subcutaneous fat, not general adiposity.
• Waist circumference: Estimates risk for diseases.
• Bioelectrical impedance: Measures body fat by measuring resistance to electrical flow.
• Other measures: Ultrasound (e.g., metabolic rate) and chemical analyses.

Prevalence

• Consensus that an obesity epidemic is underway, affecting men and women similarly.
• Commonly used measure is BMI.
• Data largely sourced from surveys (e.g., US, Worldwide, Australia, and NSW).

Prevalence Data in the USA

• CDC (Center for Disease Control) data on body weight from Behavioral Risk Factor Surveillance System (BRFSS).
• Data shows a rise in obesity prevalence over time (1990-2006).
• Studies show systematic underestimation of obesity/overweight levels in telephone surveys. Other data sources (e.g., NHANES) support similar results.

Obesity Trends Across US Adults (BRFSS data by year)

• Map data showing prevalence percentages of obesity by state across the US for multiple years.

SES, Age, Ethnicity & Obesity in the US

• Obesity prevalence varies significantly across socioeconomic backgrounds, ages, and ethnicities.

Child and Adolescent Obesity in the US

• Data showing a rise in obesity rates for children in the US.

Overweight & Obesity in the OECD

• Graph displaying past and projected rates of overweight/obesity in OECD countries.

Obesity Around the World (2016)

• Map data showing prevalence of obesity/overweight globally.

Obesity in Australia

• Prevalence of overweight/obesity for Australian adults.

Childhood Obesity and Overweight in Australia

• Prevalence of obesity/overweight across different age groups in Australia.

Adult Overweight and Obesity – NSW

• Map data showing prevalence of overweight and obesity across different regions of NSW.

Health Care Costs

• Australia: Direct health costs from obesity ~$10.7 billion annually.
• US: Direct health care costs for the obese rose significantly from 1995 to 2012.
• Obesity costs are increasing.

Medical Consequences

• Diabetes: Type 1 (not obesity related); Type 2 (directly related); obesity significantly increases risk.
• Health effects due to poorly managed Type 2 diabetes (e.g., microvascular disease, macrovascular disease).
• Other medical conditions: e.g., osteoarthritis, sleep apnoea, impotence.

Cancer

• Obese people are more likely to die from cancer.
• For some cancers, a high proportion of cases can be attributed to obesity(e.g., bowel, breast, endometrial, oesophageal, and kidney).
• Cancer detection and treatment more difficult for obese individuals.

Psychosocial Effects

• Obesity can negatively impact children and young adults, affecting their social perceptions, educational outcomes and career prospects.

Summary

• Obesity is widespread and has been increasing for the past 50 years, particularly in developed nations.
• Obesities are linked to higher medical costs and significant health problems.
• Lifestyle change can have a significant impact on health outcomes, both positively and negatively.