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Conditions · Systemic conditions

Obesity !

Obesity is a chronic disease of excess body fat that harms health, usually defined in adults by a body mass index (BMI) of 30 or more.

Updated 2026-10-30

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What it is

A chronic disease of excess body fat that harms health, usually defined in adults by a body mass index (BMI) of 30 kg/m² or more.

Who gets it

Increasing worldwide and in Latin America, including Colombia, in adults and children, linked to urbanization, ultra-processed food and less physical activity. National surveys in 13 Latin American and Caribbean countries (1998–2017) showed rising obesity, unequal by wealth and residence; in Peru, the urban–rural gap among men reached 15.8 percentage points.

Causes

  • Long-term energy intake above expenditure
  • Diet high in ultra-processed foods and sugary drinks
  • Physical inactivity and poor sleep
  • Genetic susceptibility; rare monogenic causes
  • Endocrine causes: hypothyroidism, Cushing syndrome
  • Drugs that cause weight gain (some antipsychotics, corticosteroids)

Risk factors

  • Family history of obesity
  • Sedentary work and lifestyle
  • Low income and food environment
  • Childhood obesity
  • Pregnancy-related weight gain and menopause
  • Depression and chronic stress

Pathophysiology

When energy intake exceeds expenditure, fat stores grow. Enlarged fat cells, especially visceral fat, release inflammatory cytokines and free fatty acids that cause insulin resistance. Hormonal signals that regulate appetite (leptin, ghrelin) are altered, and the body defends its higher weight.

Classification

  • BMI 25–29.9: overweight
  • BMI 30–34.9: class I obesity
  • BMI 35–39.9: class II obesity
  • BMI 40 or more: class III (severe) obesity
  • Waist circumference to assess central (abdominal) obesity; cut-offs vary by population

Symptoms and signs

  • Increased body weight and waist size
  • Shortness of breath on exertion
  • Joint pain in knees, hips and lower back
  • Snoring and daytime sleepiness (sleep apnea)
  • Skin folds with rashes, acanthosis nigricans
  • Reduced mobility and fatigue

Diagnosis

Clinical
Measuring weight, height (BMI) and waist circumference; history of diet, activity, sleep, drugs and weight course; looking for comorbidities.
Tests
Fasting glucose or HbA1c, lipid profile, liver enzymes, thyroid function when indicated, and blood pressure measurement.
Imaging
Not needed to diagnose; abdominal ultrasound may show fatty liver or gallstones.

Differential diagnosis

  • Hypothyroidism
  • Cushing syndrome
  • Fluid retention (heart, kidney or liver failure)
  • Drug-induced weight gain
  • Polycystic ovary syndrome

Goal of treatment

Achieve sustained weight loss that improves or prevents comorbidities and quality of life, rather than reaching an ideal weight.

Treatment

Lifestyle
Reduced-calorie, healthy eating pattern, more physical activity, better sleep and behavioral therapy, ideally with a multidisciplinary team.
Medical
Anti-obesity medicines when lifestyle change is not enough, such as GLP-1 receptor agonists and other drug classes approved locally.
Surgical
Bariatric (metabolic) surgery, such as sleeve gastrectomy or Roux-en-Y gastric bypass, for severe obesity or obesity with major comorbidities, under accepted criteria.
Follow-up
Long-term follow-up of weight, comorbidities and nutrition, especially after surgery.

Drugs for this condition

Complications

  • Type 2 diabetes and metabolic syndrome
  • Hypertension, coronary heart disease and stroke
  • Fatty liver disease (MASLD)
  • Obstructive sleep apnea
  • Knee and hip osteoarthritis
  • Gallstones
  • Several cancers (colon, breast, endometrium, kidney)
  • Venous insufficiency and thromboembolism
  • Depression and stigma

Prognosis

Obesity tends to relapse and needs long-term management. Even modest weight loss improves blood pressure, glucose and joint symptoms; bariatric surgery gives the largest and most durable losses.

Prevention

  • Healthy eating from childhood and limiting sugary drinks
  • Regular physical activity
  • Adequate sleep
  • Breastfeeding
  • Policies on food labelling and healthy environments

Test yourself

Think of the answer, then tap the question to see it.

How is BMI calculated and what value commonly defines obesity in adults?

Weight in kilograms divided by height in metres squared; a BMI of 30 kg/m² or more defines obesity.

Why does waist circumference add to BMI?

It reflects visceral (abdominal) fat, which is more closely linked to insulin resistance and cardiovascular risk than total weight.

What are the major comorbidities of obesity?

Type 2 diabetes, hypertension, obstructive sleep apnea, fatty liver disease, osteoarthritis, dyslipidemia and some cancers.

Which are two common bariatric procedures?

Sleeve gastrectomy and Roux-en-Y gastric bypass.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Epidemiologic and Etiologic Considerations of Obesity (StatPearls (NCBI Bookshelf), 2025); The shift of obesity burden by socioeconomic status between 1998 and 2017 in Latin America and the Caribbean: a cross-sectional series study (The Lancet. Global health, 2019) · adapted, CC BY 4.0.

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