L15 & L16 | Obesity I

Obesity I

• Aim of lecture: To outline obesity, how it's measured, prevalence in the US, worldwide, Australia, and NSW, and examine its medical and financial costs to individuals and society.

What is Obesity?

• Body uses fat cells for long-term energy storage.
• Two types of fat cells:
  • Brown fat cells (BAT): Used for heat generation, located on sides of spinal column; rich in mitochondria.
  • White fat cells: Insulate, cushion organs, long-term energy storage; 85% fat content.

White Fat Cells

• Approximately 20% of women and 15% of men is composed of white fat cells; represents roughly one month's store of energy.
• Distributed differently in men and women (women more on hips/thighs, men more on waist).
• Stored subcutaneously and around organs in both genders.
• Positive energy balance: When energy intake is more than energy expenditure results in excess energy being turned into fat which is stored in white fat cells; leading to obesity.

Measurement of Obesity

• Body Mass Index (BMI) or Quetelet's index: Most frequently used measure to estimate body fat percentage by dividing weight in kilograms by the square of height in meters.
• Example: An Australian man weighing 85 kg and 1.79 m tall would have a BMI of 26.6.
• BMI ranges:
  • Underweight: Below 18.5
  • Normal: 18.5-24.9
  • Overweight: 25.0-29.9
  • Obese: 30+ (Moderate, Severe, Very Severe)

Other Measures

• Skin fold thickness (calipers): Measures overall fat but not general adiposity, can be difficult to define.
• Waist circumference: Measures abdominal fat, useful in estimating separate risk factors for heart disease and stroke.
• Bioelectrical impedance: Indirectly estimates body fat by measuring the resistance to the flow of electricity through the body; sensitive to hydration.
• Ultrasound, chemical (metabolic rate), and computerized tomography/MRI: Other measures of body fat.

Prevalence

• A consensus that an obesity epidemic is occurring globally, affecting men and women similarly.
• Most large-scale studies use BMI as a measure.
• Data is consistently available from the US, worldwide, Australia, and NSW.

Prevalence Data in the USA

• The CDC (Center for Disease Control) provides the most comprehensive data on body weight using the Behavioral Risk Factor Surveillance System (BRFSS)
• Telephone surveys may systematically underestimate obesity levels (around 5%).
• Data consistently shows an increase in obesity prevalence from 1990 to 2006 (epidemic), with slightly more data available and more updated data from 2007-2019.

SES, Age, Ethnicity & Obesity in the US

• Obesity rates vary across different socio-economic status (SES), ages, and ethnic groups within the USA.
• Shows obesity levels increasing with age, across different socioeconomic groups, and different ethnicities.
• Significant rates across those categories.

Child and Adolescent Obesity in the US

• Obesity prevalence has been increasing in children and teenagers since the 1960s to the present day.
• Levels have doubled-tripled from around 1 in 20 to about 1 in 5.

Obesity in Australia & NZ

• Australia has a growing obesity problem.
• Significant regional variations in obesity rates; poorer areas tend to have higher rates compared with wealthier areas in urban parts of the country.
• Latest figures show 67% overweight and 31% obese.

Health Care Costs

• In Australia, direct and indirect costs associated with obesity are substantial. In the U.S., direct medical costs for obese adults have risen substantially; from 52 billion US dollars in 1995 to 178 billion in 2012 (estimates).
• This cost is mostly related to obesity-related medical conditions, for example diabetes and cardiovascular disease.

Medical Consequences

• Type II diabetes: The most prominent consequence of obesity.
• Medical conditions associated with obesity include, amongst other things, osteoarthritis, sleep apnoea, and reproductive issues.
• Cancer: Obese people face a heightened risk of dying from cancer.

Psycho-Social Effects

• Obese people may face negative judgments and stigma in society affecting their social interactions and career opportunities.
• Obese children report difficulties throughout their education and social interactions.

Summary

• Obesity rates have increased over the past 50 years in all age groups.
• Obesity has significant medical, social, and financial costs for communities.

This quiz covers the fundamental aspects of obesity, including its measurement, prevalence in various regions, and the associated medical and financial costs. Explore the types of fat cells involved and how they relate to energy storage, as well as the implications for health.