obesity

Obesity

Copyright Information

  • Copyright © 2020 by Elsevier, Inc. All rights reserved.

Objectives

  • Discuss the epidemiology and etiology of obesity.

  • Explain the health risks associated with obesity.

  • Compare the classification systems for determining a person’s body size.

  • Discuss nutritional therapy and exercise plans for the obese patient.

  • Distinguish among the medications and bariatric surgical procedures used to treat obesity.

Epidemiology of Obesity

  • About 40% of adults in the United States are obese.

  • 1 in 10 children become obese as early as ages 2 to 5.

  • Obesity rates are highest in multiple demographics:
      - Geographic Area: The South.
      - Ethnic Groups: Among blacks and Hispanics.
      - Economic Status: Among lower income and less educated individuals.

Percent of Obese Adults

  • A graphic representation of the obesity rates across states in the U.S. (Data Source: Trust for America's Health, Robert Wood Johnson Foundation; The state of obesity. 2017).

Obesity and Ethnicity

  • Obesity prevalence among different ethnic groups:
      - Overall (Both Genders): 48.4% of the total population.
      - Men: 42.3% obesity prevalence.
      - Women: 38.0% obesity prevalence.

  • Extreme obesity rates differ by ethnicity:
      - Black: 57.2% (obese), 12.6% (extreme obese).
      - Hispanic: 46.9% (obese), 12.4% (extreme obese).
      - White: 38.2% (obese), 7.6% (extreme obese).
      - Asian: 5.4% (obese), 7.1% (extreme obese).

    (Data Source: Trust for America's Health, Robert Wood Johnson Foundation; The state of obesity. 2017).

Etiology and Pathophysiology

  • The processes leading to and sustaining an obese state are complex.

  • Key points about body weight:
      - Body weight often exceeds physical requirements.
      - Abnormal increase and accumulation of fat cells are central to obesity.

  • Adipocyte Changes:
      - Increase in number (hyperplasia) and size (hypertrophy) of adipocytes.
      - Significant increases in lipid storage.
      - Preadipocytes are stimulated to become adipocytes once existing fat cell storage is exceeded.

Classification of Body Weight and Obesity

  • Primary Obesity:
      - Result of excessive caloric intake relative to the body's metabolic demands.

  • Secondary Obesity:
      - Related to chromosomal and congenital anomalies, metabolic problems, CNS lesions, or drug effects (e.g., corticosteroids, antipsychotics).

Genetic/Biologic Basis

  • Evidence shows significant genetic and biologic susceptibility factors influenced by environmental and psychosocial factors.

  • These factors are interrelated rather than isolated.

  • Specific genes linked to obesity include:
      - "Energy-thrifty" genes.
      - FTO gene: Linked with increased appetite, reduced satiety, and higher caloric intake among individuals carrying a specific allele.

Physiologic Regulatory Mechanisms

  • Research is focused on the mechanisms controlling:
      - Eating behavior.
      - Energy metabolism.
      - Body fat metabolism.

  • Hormones and Peptides:
      - Leptin: Suppresses appetite and enhances fat metabolism.
      - Ghrelin: Regulates appetite by inhibiting leptin; associated with compulsive eating behaviors.

  • Obesity leads to two major consequences:
      - Increase in fat mass.
      - Production of adipokines, affecting insulin resistance, dyslipidemia, hypertension, immune response, and potential cancer predisposition.

Environmental Factors

  • Contributing factors to obesity include:
      - Greater access to nutritionally poor foods.
      - Underestimating caloric intake.
      - Lack of physical exercise.
      - Low socioeconomic status.

Psychosocial Factors

  • Food is often associated with various reasons including:
      - Emotional satisfaction, particularly from childhood associations.
      - Altered sense of satiety.
      - Mindless eating behaviors influenced by social settings.

Health Risks Associated with Obesity

  • Health problems are significantly more prevalent among obese individuals, including:
      - Increased mortality, particularly with visceral fat.
      - Decreased quality of life, with most conditions improving upon weight loss.

  • Comorbidities Associated with Obesity:
      - Psychosocial Issues: Depression, low self-esteem, increased suicide risk, discrimination, social isolation.
      - Endocrine/Metabolic: Type 2 diabetes mellitus, metabolic syndrome, polycystic ovary syndrome.
      - Respiratory: Obesity hypoventilation syndrome, sleep apnea, asthma, pulmonary hypertension, exercise intolerance.
      - Reproductive Risks (Women): Menstrual irregularities, infertility, gestational diabetes.
      - Cardiovascular Diseases: Includes hyperlipidemia, sudden cardiac death, heart failure, left ventricular hypertrophy, among others.
      - Gastrointestinal: Nonalcoholic steatohepatitis (NASH), gallstones, gastroesophageal reflux disease (GERD).
      - Genitourinary: Include chronic kidney disease and stress incontinence.
      - Musculoskeletal: Osteoarthritis, chronic low back pain, and gout.
      - Cancer Risks: Includes esophageal, colorectal, breast, and other types of cancers.

Classification of Body Weight and Obesity

  • Methods of Assessment:
      - Body Mass Index (BMI)
      - Waist circumference.
      - Waist-to-hip ratio (WHR).
      - Body shape classification.

  • BMI Classification:
      - Underweight: BMI < 18.5 kg/m².
      - Normal weight: BMI 18.5 - 24.9 kg/m².
      - Overweight: BMI 25 - 29.9 kg/m².
      - Obese: BMI ≥ 30 kg/m².
      - Extremely obese: BMI ≥ 40 kg/m².