Obesity
Excess body fat that harms health, usually defined by a BMI of 30 or more (lower thresholds for some ethnic groups). It is a chronic disease driven by biology and environment, not simply willpower.
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Over 1 billion people worldwide.
Causes
- Energy intake exceeding expenditure over time, shaped by genes, appetite hormones, environment, sleep, stress and medicines
Risk factors
- Energy-dense processed food environment
- Sedentary lifestyle
- Genetics
- Poor sleep
- Certain medicines (antipsychotics, steroids)
- Hypothyroidism (rarely a major cause)
Symptoms
- Excess weight
- Breathlessness, joint pain, snoring, reduced mobility
Diagnosis — tests and examinations
- BMI and waist circumference
- Screening for diabetes, blood pressure, lipids, fatty liver, sleep apnoea
Treatment
Medicines and medical treatment
- GLP-1 receptor agonists (semaglutide) and tirzepatide produce 15–20% weight loss
- Orlistat
- Treatment of related conditions
Operations and procedures
- Bariatric surgery (sleeve gastrectomy, gastric bypass) for severe obesity
Self-care, home remedies and lifestyle
- Sustainable calorie-reduced diet
- Regular physical activity
- Sleep and stress management
- Behavioural support programmes
Possible complications
- Type 2 diabetes
- Heart disease and stroke
- Some cancers
- Osteoarthritis
- Sleep apnoea
- Fatty liver disease
Prevention
- Healthy food environments, activity and sleep from childhood
Outlook
Even 5–10% weight loss brings significant health benefits.
When to see a doctor
See a doctor for support with weight management and screening for related conditions.
Sources and further reading
These sources cover this condition. They have not been checked against every statement on this page.
Related conditions
Educational overview, not medical advice. Treatment varies by person and location. Consult a qualified health professional for diagnosis or care. Read our content and model notes and privacy information.