Obesity

Descriptive text is not available for this image Basics

Description

  • A complex, multifactorial, chronic disease characterized by excess or dysfunctional adipose tissue that impairs health
  • Obesity is categorized as (1):
    • Preclinical: excess adiposity with preserved organ function, associated with increased risk of clinical obesity and related diseases (e.g., type 2 diabetes, cardiovascular disease [CVD])
    • Clinical: excess adiposity with organ dysfunction (e.g., hypertension [HTN], sleep apnea) or significant limitations in daily living
  • Traditionally quantified using body mass index (BMI) (BMI ≥30 kg/m2), although BMI should not be used as a sole criterion for diagnosis:
    • Overweight: 25.0 to 29.9 kg/m2
    • Class 1 obesity: 30.0 to 34.9 kg/m2
    • Class 2 obesity: 35.0 to 39.9 kg/m2
    • Class 3 obesity (severe obesity): ≥40 kg/m2

Epidemiology

Incidence

Obesity rises in the early 20s and peaks at 40 to 59 years old.

Prevalence

  • Obesity affects 40.3% of the U.S. population (National Health and Nutrition Examination Survey [NHANES]), with similar rates in men (39.2%) and women (41.3%).
  • Severe obesity (BMI ≥40) affects 9.4%, more common in women across all age groups.
  • In children and adolescents (ages 2 to 19 years), prevalence is 19.7%, increasing with age and peaking in adolescence.

Pediatric Considerations

  • The United States Preventive Services Task Force (USPSTF) recommends obesity screening in children ≥6 years old, with referral to intensive behavioral interventions for positive cases (grade B).
  • CDC age- and sex-specific BMI percentiles:
    • Overweight: BMI ≥85th to <95th percentile
    • Class I obesity: BMI ≥95th to 119th percentile
    • Severe obesity: class II: BMI ≥120th to 139th percentile of the 95th percentile; class III: BMI ≥140th percentile of the 95th percentile
  • Obesity during adolescence is strongly associated with obesity in adulthood, and increases risk of musculoskeletal injuries, mental illness, low self-esteem, and reduced quality of life.

Etiology and Pathophysiology

  • Multifactorial process involving genetic, environmental, behavioral, and psychosocial factors causing energy imbalance
  • Adipocytes produce adiponectin and leptin: adiponectin improves insulin sensitivity; leptin deficiency is linked to severe obesity.
  • Adipocyte hypertrophy drives local and systemic inflammation.
  • Obesity alters neuronal signaling, reducing satiety.

Genetics

  • Syndromes like Prader-Willi and Bardet-Biedl are rare causes.
  • Multiple genes influence obesity and weight loss response to diet.

Risk Factors

Parental obesity, sedentary lifestyle, poor nutrition (especially high-calorie foods), limited access to fresh produce/foods, stress and mental illness

General Prevention

  • Encourage ≥150 minutes/week of moderate activity (e.g., 30 minutes of exercise, 5 days per week), and a balanced diet with controlled portions.
  • Avoid or eliminate calorie-dense and nutrient-poor foods such as sugary drinks and processed items.
  • Early preventive counseling, especially in youth through motivational interviewing and using preferred weight-related terminology

Commonly Associated Conditions

  • Type 2 diabetes, HTN, hyperlipidemia
  • Coronary artery disease (CAD), congestive heart failure
  • Obstructive sleep apnea
  • Osteoarthritis, sports-related injuries
  • Nonalcoholic fatty liver disease
  • Chronic kidney disease
  • Mood disorders: anxiety, depression
  • Cognitive impairment and dementia
  • Polycystic ovarian syndrome

Geriatric Considerations
Aging leads to changes in body composition including sarcopenia, reduced bone mineral density, and increase visceral fat, leading to frailty, impaired mobility, and higher cardiometabolic risk despite possible normal BMI.Pregnancy Considerations

  • >50% of women enter pregnancy with overweight or obesity, increasing the risk of gestational diabetes, preeclampsia, cesarean delivery, stillbirth, and prolonged neonatal hospitalizations.
  • Prepregnancy BMI ≥30 warrants counseling and weight optimization.
  • Pregnant women with obesity should receive screening for gestational diabetes and sleep apnea at the first prenatal visit.
  • Recommended gestational weight gain is 11 to 20 pounds for singleton pregnancies

There's more to see -- the rest of this topic is available only to subscribers.