Overview
This lecture discusses the evolution, causes, and consequences of body fat and obesity, highlighting the shift from survival advantage to global health epidemic.
Evolutionary Role and History of Body Fat
- Bodily fat evolved primarily as a method for reserving food during periods of scarcity.
- Natural selection favored genes for fat storage due to historical chronic malnutrition.
- Negative health impacts of excess body fat were not recognized until the 18th century.
Rise of Obesity
- Improved food availability in recent centuries led to healthier populations and increased rates of overweight and obesity.
- By the mid-19th century, the health risks of obesity were recognized.
Defining Overweight vs. Obesity
- Overweight is defined as a body mass index (BMI) between 25 and 29.9.
- Obesity is defined as a BMI over 30.
- BMI is calculated using weight and height but does not account for muscle mass or waist circumference.
Causes of Obesity
- Obesity is mainly caused by an energy imbalance: more calories consumed than expended.
- Lifestyle factors include insufficient physical activity and consumption of calorie-dense foods.
- Environmental factors like limited access to healthy foods increase risk, especially in disadvantaged communities.
- Genetics and gut bacteria composition also contribute to obesity risk.
Global Impact and Health Risks
- Obesity raises the risk of diabetes, heart disease, stroke, high blood pressure, and cancer.
- The prevalence of obesity is increasing in all demographics and countries, particularly among children.
- Recovery from obesity is challenging due to metabolic and hormonal changes.
Treatment and Prevention
- Sustained lifestyle changes can improve health outcomes related to obesity.
- Medical interventions such as bariatric surgery can further help reduce obesity-related health risks.
- Global and coordinated preventive measures are needed to combat the obesity epidemic.
Key Terms & Definitions
- Body Fat — Stored energy reserves in the body.
- BMI (Body Mass Index) — A calculation using weight and height to estimate healthy body weight.
- Obesity — A condition marked by excessive body fat, defined as a BMI above 30.
- Energy Imbalance — Consuming more calories than one expends, leading to fat storage.
Action Items / Next Steps
- Review BMI calculation and its limitations.
- Reflect on factors contributing to obesity in different populations.
- Prepare for class discussion on possible public health strategies to address obesity.