KIN240: Principles of Biobehavioral Health Lecture Notes

Body Composition Overview

  • Fat as a Concept

    • Fat is something that individuals "have," not something that defines them.

    • Societal misconceptualizations lead to problematic views on body composition.

    • Common phrases such as "I feel fat. I need to lose weight" highlight misunderstandings about body composition.

Body Image and Body Dysmorphia

  • Social Taboos Around Body Composition

    • Discussion of body weight and composition is often taboo, leading to misassessments of health and wellness.

    • Post-weight loss, individuals often still report feelings of being "fat," indicating a disconnect between self-perception and actual body state.

  • Understanding Body Dysmorphia

    • Body Dysmorphia is a natural phenomenon where imperfections in physical appearance are perceived.

    • Body Dysmorphic Disorder (BDD) is a clinical condition where individuals are overly preoccupied with perceived flaws (more than 3 hours/day) leading to functional impairments.

    • Shifting focus from appearance to functional ability can mitigate body dissatisfaction.

Models of Body Composition

  • One Component Model

    • Utilizes overall body mass as an inferred measure of body composition, which is misleading and oversimplified.

    • Statements about weight loss goals (e.g., "I just need to lose ten pounds") are often arbitrary and unrelated to health.

  • Two Component Model

    • Divides body composition into fat mass and fat-free mass (FFM).

    • Healthy body fat levels:

    • 6-24% for males

    • 9-31% for females

    • Low body fat (<6% for males, <9% for females) is linked to serious health risks.

  • Four Component Model

    • Separates body composition into fat, water, protein, and mineral mass.

    • Typical body mass distribution includes:

    • 21% fat

    • 58% water

    • 16% protein

    • 7% mineral

    • Misconceptions about body cleanses and diuretics; they primarily affect water mass, not fat mass.

  • Anatomical Model

    • Distinguishes fat mass into storage fat (14% of body mass) and essential fat (7% of body mass).

    • Storage fat divides further into visceral and subcutaneous fat.

    • Fat-free mass includes muscle (38%), bone (13%), skin (11%), organs (10%), and blood mass (7%).

    • Males generally have more muscle mass, while females have higher essential fat for biological functions.

Fat Types and Adipose Tissue

  • Types of Adipose Tissue

    • White Adipose Tissue (WAT):

    • Specialized for energy storage.

    • Can undergo hypertrophy (increase in size) and hyperplasia (increase in number).

    • Brown Adipose Tissue (BAT):

    • Specialized for heat generation through non-shivering thermogenesis; contains many mitochondria.

    • Beige Adipose Tissue:

    • Can function as both WAT and BAT, adapting to energy storage or heat generation based on stimuli (e.g., cold exposure).

Assessment of Body Composition

  • Methods of Assessment

    • Include bioelectric impedance, plethysmography, DEXA scans, CT, and MRI for varying levels of cost, accuracy, and discomfort.

    • Body Mass Index (BMI): Defined by extBMI=racextWeightinkgextHeightinm2ext{BMI} = rac{ ext{Weight in kg}}{ ext{Height in m}^2}; used as a screening tool for health risks associated with body fat.

    • BMI classifications include:

      • Underweight: <18.5

      • Normal: 18.5-24.9

      • Overweight: 25-29.9

      • Obese: ≥30

    • Revised criteria for Asian populations:

      • Underweight: <18.5

      • Normal: 18.5-22.9

      • Overweight: 23-27.4

      • Obese: ≥27.5

  • Caveats of BMI

    • Criticisms include overestimation or underestimation of adiposity due to differences in muscle density and aging effects.

Health Impacts of Obesity

  • Global Implications

    • Approximately 2.8 million deaths annually linked to obesity as a contributor.

    • Rapidly increasing prevalence of obesity globally; significant contributor to health problems.

  • Health Complications

    • Associated with diabetes (RR=7), coronary heart disease (RR=6), certain cancers (RR: 1.5-3), respiratory issues (RR: 1.2-2), osteoarthritis, and increased fracture risk.

    • Increased risk of mortality correlates with obesity; 1% increase in death risk for each pound gained after obesity onset.

Obesity Prevention Efforts

  • Stigmas and Misconceptions

    • The conflict between healthy body image campaigns and obesity prevention efforts is often misinterpreted.

    • Health promotion must encompass broader behavioral changes, not just exercise or weight loss directives.

  • Primary vs. Tertiary Prevention

    • Primary prevention focuses on lifestyle changes for health without emphasizing weight loss.

    • Tertiary prevention involves behavioral modification programs under supervised settings to reduce obesity risks.

    • Surgical options have high failure rates and potential complications, emphasizing the importance of comprehensive health education.

Additional Reading

  • Kajimura, S., Spiegelman, B. M., & Seale, P. (2015). Brown and Beige Fat: Physiological Roles Beyond Heat Generation. Cell Metabolism, 22(4), 546-559.

  • Nammi, S., Koka, S., Chinnala, K. M., & Boini, K. M. (2004). Obesity: An Overview on Its Current Perspectives and Treatment Options. Nutrition Journal, 3(1), 1-8.