Overview
Obesity is a chronic, complex disease characterized by excess body fat that can impair health, most commonly assessed in adults using a body mass index (BMI) of 30 or higher.
Disease Summary
- Category
- Non-Communicable Disease
- Cause
- A complex interaction of genetic, environmental, behavioural, and psychosocial factors leading to excess body fat
- Transmission
- Not applicable; obesity is a non-communicable condition and cannot be spread between people
- Body System
- Whole Body
- Preventable
- Yes
- Curable
- No
Symptoms
Associated Signs
Obesity is primarily assessed through measurement rather than symptoms, though the following can accompany it.
Excess Body Fat
The defining feature of obesity, most often assessed using body mass index (BMI) alongside other measurements.
Reduced Physical Endurance
Difficulty with physical activity or shortness of breath during exertion can occur.
Joint Discomfort
Extra weight can place added strain on weight-bearing joints such as the knees and hips.
Sleep Disturbances
Snoring or disrupted sleep can be associated with excess weight, particularly around the neck and airway.
Danger Signs
Seek prompt medical attention if any of the following occur.
Chest Pain or Shortness of Breath
May indicate a cardiovascular complication and needs urgent evaluation.
Sudden Leg Swelling or Pain
Can indicate a blood clot, which is more common in people with obesity, and needs prompt medical attention.
Signs of Very High Blood Sugar
Excessive thirst, urination, or confusion may indicate undiagnosed or poorly controlled diabetes.
Loud Snoring with Pauses in Breathing
May indicate sleep apnea, a condition that needs medical evaluation.
Diagnosis
Clinical Assessment
Diagnosis involves measuring body mass index (BMI) alongside a review of overall health and risk factors.
Body Composition Measurement
Waist circumference and other measurements can provide additional information about health risk beyond BMI alone.
Screening for Related Conditions
Blood tests can screen for conditions commonly associated with obesity, such as diabetes and high cholesterol.
Laboratory Tests
Body Mass Index (BMI) Calculation
A screening tool calculated from height and weight, used to categorize weight status.
Fasting Blood Glucose
Screens for type 2 diabetes, which is more common in people with obesity.
Lipid Panel
Checks cholesterol and triglyceride levels, which can be affected by excess weight.
Liver Function Tests
Screens for fatty liver disease, a condition associated with obesity.
Treatment
Behavioural and Lifestyle Support
Structured support around nutrition, physical activity, and behaviour change is the foundation of obesity management.
Medical or Surgical Treatment
Medication or, in some cases, weight-loss surgery may be recommended alongside lifestyle changes for certain individuals.
Prevention
Build regular physical activity into daily life
Regular movement supports a healthy weight and offers many other health benefits.
Choose a balanced diet
Eating a variety of whole foods, including fruits, vegetables, and whole grains, supports overall health.
Support healthy environments for children
Access to healthy food and safe spaces for physical activity, especially in schools, helps prevent childhood obesity.
Seek support for gradual, sustainable change
Working with a healthcare provider on realistic, individualized goals supports long-term success.
Risk Factors
High Risk
These factors substantially increase the likelihood of developing obesity.
- Family history of obesity
- Limited access to affordable healthy food
- Certain medical conditions or medications
Increased Risk
These factors are associated with a moderately higher risk of obesity.
- Sedentary lifestyle
- Limited access to safe spaces for physical activity
- Chronic stress
Additional Contributing Factors
Other factors linked with an increased likelihood of obesity.
- Insufficient sleep
- Certain hormonal conditions
- Low socioeconomic status
Complications
Type 2 Diabetes
Excess body fat increases the risk of insulin resistance and type 2 diabetes.
Cardiovascular Disease
Obesity increases the risk of high blood pressure, heart disease, and stroke.
Certain Cancers
Obesity is linked to an increased risk of several types of cancer.
When to Seek Medical Care
Chest Pain or Shortness of Breath
May indicate a cardiovascular complication and needs urgent evaluation.
Sudden Leg Swelling or Pain
Can indicate a blood clot and needs prompt medical attention.
Signs of High Blood Sugar
Excessive thirst or urination may indicate diabetes and should be evaluated.
Loud Snoring with Breathing Pauses
May indicate sleep apnea and needs medical evaluation.
Prognosis
Manageable with Long-term Support
Many people see meaningful health improvements with sustained lifestyle changes and, when appropriate, medical treatment.
Chronic, Relapsing Condition
Obesity often requires ongoing management, since weight regain is common without continued support.
Reduced Complication Risk with Treatment
Even modest, sustained improvements can meaningfully reduce the risk of related health complications.
Differential Diagnosis
Hypothyroidism
An underactive thyroid can contribute to weight gain and should be considered, especially with other related symptoms.
Cushing's Syndrome
A hormonal condition that can cause weight gain, particularly around the face and abdomen.
Polycystic Ovary Syndrome (PCOS)
A hormonal condition in women that can contribute to weight gain and is associated with insulin resistance.
Medication-related Weight Gain
Certain medications, such as some antidepressants or steroids, can contribute to weight gain as a side effect.
References
World Health Organization (WHO)
WHO fact sheet on the causes, health impacts, and prevention of obesity and overweight.
World Health Organization (WHO)
WHO’s central resource on obesity as a public health challenge.
World Obesity Federation
Global data and analysis on the prevalence and trends of obesity.
Frequently Asked Questions
Is obesity just about willpower?
No. WHO recognizes obesity as a complex, chronic disease resulting from genetic, environmental, and social factors, not simply personal choices.
Is BMI the only way to diagnose obesity?
No. BMI is a useful screening tool, but healthcare providers often consider other measurements and overall health when assessing obesity.
Can obesity be reversed?
Meaningful health improvements are possible with sustained management, though obesity is generally considered a chronic condition requiring ongoing, individualized care.
Does obesity always cause health problems?
Obesity increases the risk of several health conditions, but individual risk varies, which is why a healthcare provider’s assessment is important.