
What are the causes of obesity?
Obesity is a complex disease and there are many causes of obesity. Learn some of the reasons for obesity and how they affect how obesity is managed.
Obesity is a disease that develops when there's an excess amount of body fat. It's a chronic disease, or a long-lasting condition. Chronic diseases may require ongoing medication attention or may limit activities and daily living, or both. Obesity is linked to other chronic diseases, such as heart disease, cancer, stroke, diabetes, and many more. Obesity is actually linked to more than 200 comorbidities. It's also a serious condition (with its own symptoms, complications, and causes) on its own.
To find out if you're living with obesity and to get a formal obesity diagnosis, it's important to talk to your doctor. One simple way to screen for obesity is to calculate your Body Mass Index (BMI).
The Body Mass Index (BMI) classifies underweight, overweight, and obesity in adults based on their height and weight. Here you can see the different BMI classes for who is considered a person with obesity.
BMI Classification | Underweight — Below 18.5 kg/m² |
Normal — 18.5–24.9 kg/m² | |
Overweight — 25.0–29.9 kg/m² | |
Obesity Class I — 30.0-34.9 kg/m² | |
Obesity Class II — 35.0–39.9 kg/m² | |
Obesity Class III — Above 40 kg/m² |
Having an excess amount of fat on the body is the most obvious symptom of obesity. But, there are also other symptoms you may experience if you're living with obesity. These can include:
If these symptoms sound familiar, it may be a good idea to talk to your doctor. Understanding obesity and your own situation will be helpful when you explore what you can do to help you manage weight and keep it off.
There are many things that can cause a person to gain weight and develop obesity. Health professionals recognise that obesity is a disease that's caused by genetic, environmental, and behavioral factors combined.
Talk to your weight management provider about treatment options that could prevent the weight you lose from coming back.
ZA25OB00137, June 2025