Obesity: Definition, Causes, and BMI Classification

Obesity Overview

• Obesity defined as a complex chronic disease, characterized by dysfunctional or excess body fat (adiposity), impairing health
• Individual differences in body composition, fat distribution, and function make the threshold for adiposity-impaired health variable among adults
• Causes of obesity are complex, resulting from interactions between genetic, biological, behavioral, psychosocial, and environmental factors

Learning Outcomes

• Define obesity
• Identify determinants of obesity (biological, environmental, behavioral)
• Discuss obesity assessment for pediatric and adult patients
• Identify the associations between obesity and physical and mental health
• Discuss the stigma around obesity and weight bias
• Describe treatments for obesity and their benefits

BMI Classification

• BMI is a measurement of body mass index
• BMI is used to classify individuals as underweight, normal, overweight, pre-obese, obese class 1, 2, or 3, based on values for kg/m²
• Additional classification (cutoff points) are provided
  • Underweight: <18.50
  • Normal: 18.50 - 24.99
  • Overweight: ≥ 25.00
  • Pre-obese: 25.00 - 29.99
  • Obese class I: 30.00 - 34.99
  • Obese class II: 35.00 - 39.99
  • Obese class III: ≥40.00

Genetic Causes of Obesity

• Substantial evidence supports the heritability of obesity
• Research on both rare and common forms of obesity has identified genes playing significant roles in its etiology
• Twin studies show a high degree of similarity in weight for identical twins reared apart, suggesting a heritability ratio of approximately 70%.
• Adopted children's BMI is related to biological parents, but not adoptive parents
• Environmental factors can still affect the relationship

Environmental Influences on Obesity

• Obesogenic environment's characteristics, which promote obesity
  • Limited access to recreational facilities in schools and local areas
  • Availability of unhealthy food options such as snacks, drinks and eating out
  • Limited availability of healthy food Factors contributing to the obesogenic environment
    • Lack of school facilities -Few local playing areas -Widely available food -unsafe streets
    • Few cycle routes

Obesity Assessment for Pediatric and Adult Patients;

• BMI is a commonly used measure but not comprehensive, as it doesn't consider age, gender, nor body frame
• More thorough assessment requires a wider range of measures for better understanding.
• Waist circumference
• Ratio of hip to waist
• Fat distribution around the abdomen
• Pediatric assessment can consider different weight-for-age standards (WHO 2007, CDC 2000, Cole-IOTF) and these classifications can vary.

Health Implications of Obesity

• Obesity can have substantial effects on mental health (e.g., stigma leading to low self-esteem, depression) and physical health (e.g., cardiovascular disease, diabetes, joint trauma)

Weight Stigma and Bias

• Stigma surrounding obesity: a negative aspect that impacts people with obesity
• Stigma and health: corrosive, affecting those experiencing it and contributing to poor health outcomes and impacting health care utilisation
• Disease-related stigma: labelling, bias, stereotyping, discrimination and/or prejudice that can accompany a health condition.
• Consequences of weight bias and stigma: poor body image, stress- induced pathophysiology, maladaptive eating patterns, avoidance of physical activity, avoidance of healthcare, lower quality of life, depression, anxiety and suicidal thoughts.
• Weight bias is unique as eating is necessary for survival whereas other stigmatized conditions aren't

What can be done?

• Explore beliefs, and weight bias
• Don't assume overeating behavior; believe patient’s dietary intake and physical activity
• Understand complex genetics and biology of obesity
• Leave out cookie-cutter advice to eat less and exercise more to lose weight
• Chronic disease model of care; focus on health gains, not just weight loss
• Manage expectations, yours, colleagues, and patients

Weight Treatment Options (Pharmacological)

• Indications: BMI ≥ 30 or BMI ≥ 27 and comorbidities (e.g., diabetes)
• Pharmacotherapy is an adjunct to diet and exercise
• Works on hormonal changes related to obesity -GLP-1 agonists (e.g., semaglutide) -Reduce fat absorption (e.g., orlistat) -Work on CNS and appetite centers (e.g., phentermine)

Weight Treatment Options (Surgery)

• Indications: BMI ≥ 35 kg/m² with one or more obesity-related complications or BMI ≥ 40 kg/m² regardless of comorbidity., or refractory to non-surgical weight loss with obesity-related complications (especially Type 2 Diabetes)
• Different procedures include gastric bypass, sleeve gastrectomy or adjustable gastric banding.

Role of Health Professionals

• Communication is key, crucial in weight management
• Explain health risks, and understand reason for obesity
• Identify barriers to weight loss, develop weight loss targets, and support by providing training and information, including written materials, community-based groups, and online resources
• Monitor weight changes and provide pharmacological and/or referral support (surgery) when needed according to BMI

Language Considerations

• Positive and negative language is critically important
• Effective communication relies on positive language choices to foster a supportive environment.

Other Important Considerations

• BMI measurement is a conversation starter, but reduction may not be the overall goal
• Exploring considerations such as sleep, stress, lifestyle, financial issues, and pain is crucial to help understand contributing factors to obesity.
• Understand the factors that influence weight gain
• Weight management programs can be successful, for example in diabetes remission programs.

This lesson defines obesity as a complex chronic disease resulting from interactions between various factors. It covers learning outcomes such as identifying obesity determinants, assessment, and associations with health. It also discusses BMI classification and weight bias.