Obesity is a complex chronic condition that impacts both physical and mental health. It is caused by a variety of physical, environmental, hormonal and psychological causes. But diagnosing obesity involves more than just stepping on a scale.
While BMI (Body Mass Index) is a useful tool to screen for obesity, it doesn’t tell the full story.
Diagnosing obesity involves considering multiple factors, including how your weight affects your health, and your risk of developing weight-related conditions like heart disease and diabetes.
What is BMI and How is It Used?
BMI is calculated by dividing your weight (in kilograms) by your height (in metres squared). It gives a general idea of whether you’re within a healthy weight range. Here’s a breakdown of the BMI categories:
- Healthy weight: BMI of 18.5 to 24.9
- Overweight: BMI of 25 to 29.9 (or 23-24.9 for those of Asia-Pacific backgrounds)
- Obesity (Class 1): BMI of 30 to 34.9 (or 25-29.9 for those of Asia-Pacific backgrounds)
- Obesity (Class 2): BMI of 35 to 39.9 (or 30-34.9 for those of Asia-Pacific backgrounds)
- Severe Obesity (Class 3): BMI of 40 or higher (or 34.9 or higher for those of Asia-Pacific backgrounds)
While BMI is a useful starting point, it’s important to note that it doesn’t take into account muscle mass, bone density, or fat distribution.
For example, athletes with high muscle mass may have a high BMI but low body fat. This is why BMI should be used alongside other assessments.
Waist Circumference and Visceral Fat
Your GP may also measure your waist circumference to assess how much fat is stored around your abdomen.
This type of fat, known as visceral fat, surrounds your organs and is more closely linked to conditions like heart disease and type 2 diabetes.
A high-risk waist circumference is:
- Men: greater than 102 cm (40 inches)
- Women: greater than 88 cm (35 inches)
For some ethnic groups, the cutoff points may be lower, as people of South Asian or African-Caribbean descent may have a higher risk of health issues at smaller waist sizes.
Health Conditions Related to Obesity
Diagnosing obesity isn’t just about numbers; it’s about understanding how your weight affects your health. You may have a BMI over 30 for example, but not be diagnosed with obesity if your weight is not affecting your health.
To diagnose obesity, your GP will assess whether you have any weight-related conditions, such as:
- High blood pressure
- Type 2 diabetes
- High cholesterol
- Sleep apnoea
- Joint pain or osteoarthritis
- Heart disease
- Fatty liver disease
These conditions, along with your BMI and waist circumference, help to confirm an obesity diagnosis and guide the treatment plan.
Is Bariatric Surgery Right for You?
If you’re thinking about how obesity might be affecting your health and wondering if bariatric surgery could be the next step, you’re not alone. Our course is designed to help you explore whether bariatric surgery is the right choice for you, guiding you through every stage of the nutritional journey —from understanding the procedure to what to expect nutritionally after surgery.
Join the waiting list four our upcoming Nourished Bariatrics courses to receive updates and learn more, so you can make an informed decision at your own pace.. It is caused by many
