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About obesity

More about obesity: Definition, symptoms and diagnosis

Obesity is a chronic disease that can seriously impact your quality of life and wellbeing. Here’s everything you need to know about obesity - including signs and symptoms of obesity, diagnosis, and an accurate obesity definition.

4 min. read

What is Obesity?

Obesity is defined by medical professionals as a complex and progressive disease where excess or abnormal body fat causes and increases the risk of long-term health complications.

The most common way to classify obesity is by using the Body Mass Index (BMI) - a measure calculated by dividing weight in kilograms by the square of height in meters. In most people, a BMI of 25 kg/m² or more represents an increased risk of obesity and overweight symptoms and requires additional evaluation. While BMI does not qualify an obesity diagnosis, a BMI of 30 kg/m2 or more is associated with increased cardiovascular risk and mortality, and anyone with a BMI of 30 or above should consult their doctor for support.

BMI is an objective way to classify underweight, normal weight, overweight, and obesity in adults. Within the official obesity definition, there are different classifications of the disease.

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  


These classifications are a standardised measurement and form part of an internationally recognised obesity definition. 

What are the symptoms commonly associated with obesity?

In addition to a BMI of 30 kg/m² or more, there are other symptoms of obesity that can impact your day-to-day life.  Obesity symptoms may include:

  • Difficulty doing physical activity like climbing stairs
  • Breathlessness
  • Increased sweating
  • Snoring
  • Feeling tired regularly
  • Joint pain
  • Back pain
  • Low confidence and self-esteem
  • Feeling isolated
  • Depression, anxiety, and mood disorders

If you're experiencing any of these symptoms, it's a good idea to talk to your doctor.

How is obesity diagnosed?

An obesity diagnosis may be an important step in treating and managing obesity the condition.

Diagnosing obesity usually involves an assessment of lifestyle, medical and family history, a physical examination and/or laboratory tests.

To assess lifestyle, medical and family history, a healthcare provider may ask questions related to your:

  • Ethnicity
  • Family history
  • Diet
  • Physical activity and exercise habits
  • Eating disorders
  • Depression and other mood disorders
  • Genetics
  • Drugs
  • Chronic stress
  • Smoking habits

A physical exam

A physical examination may also be necessary to support a formal diagnosis of obesity. Guidelines recommend doctors carry out an Edmonton Obesity Staging System (EOSS), which is a measure of the mental, metabolic and physical impact of obesity. This can then help your doctor find the right treatment plan for you.  

This may include:

  • Measuring weight, height, and waist circumference
  • Measuring blood pressure
  • Assessing if you have obesity-related diseases (for example, diabetes, hypertension, mental health disorders, osteoarthritis, respiratory disease, and others)
  • Checking for obesity skin problems such as acanthosis nigricans (dry, dark patches of skin that can be a sign of insulin resistance)

Laboratory tests

Lastly, laboratory tests may be administered to identify the underlying signs and symptoms of obesity. Your doctor will select what laboratory tests to run depending on your case and assessment needs. 

Laboratory tests may be used to assess:

  • Fasting blood glucose (to measure your sugar levels when they are at their lowest)
  • Cholesterol test (including total, HDL and LDL cholesterol, triglycerides)
  • Uric acid (a normal waste product that passes through your kidneys and leaves your body in urine)
  • Thyroid function and endocrine evaluation (to assess your hormone levels)
  • Liver function
  • Liver investigation (including ultrasound or biopsy)
  • Non-alcoholic fatty liver disease (NAFLD) or other liver pathology
  • Cardiovascular assessment
  • Sleep laboratory investigation for sleep apnoea (when your breathing stops and starts in your sleep)

Expectations and treatment options

If you live with overweight or obesity, you may have experienced weight-bias or had stigmatised conversations with a doctor or healthcare provider in the past. This is because obesity as a disease is a relatively new area for scientific research and development. This has led to a long period of misunderstanding by society and healthcare professionals alike. The important thing to remember is there is a lot of progress being made to make the treatment of obesity a priority for healthcare teams all over the world. In fact, some countries now have specialised weight management clinics for treating overweight and obesity. 

Find your local weight management provider

Talk to your weight management provider about treatment options that could prevent the weight you lose from coming back.

When discussing obesity with your doctor, they may want to discuss your expectations and treatment options for managing obesity.

Together with your doctor, you may address how willing you are to manage weight, previous attempts to manage symptoms of your condition, the benefits of maintainable weight loss and potential complications and health consequences associated with obesity.

These classifications are a standardised measurement and form part of an internationally recognised obesity definition. 

What causes obesity?

A simplistic explanation is an energy imbalance, wherein calories taken in are significantly higher than the calories used. In reality, the causes of obesity are complex and influenced by a mix of genetic, environmental and behavioural factors. As one potential cause, evidence points to inherited traits that disrupt metabolic and weight regulating mechanisms in the body. Learn more about the causes of obesity here.

To understand if you are living with obesity and get professional advice, it is important to talk to your doctor or to an obesity specialist. By seeking professional help, you will be better equipped to manage your weight and symptoms of obesity in a healthy and sustainable way.

  1. Wharton, S, Lau, D et al. Obesity in adults: a clinical practice guideline. Canadian Medical Association Journal. 2020; 192(31) 875-891
  2. Rueda-Clausen CF, Poddar M, Lear SA, Poirier P, Sharma AM. Canadian Adult Obesity Clinical Practice Guidelines: Assessment of People Living with Obesity. https://obesitycanada.ca/guidelines/assessment/. Last accessed: 22 November 2022
  3. Lopez-Jimenez F, Almahmeed W et al. Obesity and cardiovascular disease: mechanistic insights and management strategies. A joint position paper by the World Heart Federation and World Obesity Federation. Eur J Prev Cardiol. 2022; 0 1-20
  4. Obesity. NHS. https://nhs.co.uk/conditions/obesity. Last accessed: 22 November 2022
  5. Clemens EL et al. Diagnosing Obesity as a First Step to Weight Loss: An Observational Study. Obesity 28(12):2305-2309.
  6. Yumuk V et al. European Guidelines for Obesity Management in Adults. Obesity Facts 2015;  8(6):402-424.
  7. de Wit LM et al. Depressive and anxiety disorders and the association with obesity, physical, and social activities. Depression and anxiety 2010; 27(11):1057-1065
  8. Caterson, ID, Alfadda, AA et al. Gaps to bridge: Misalignment between perception, reality and actions in obesity. Diabetes Obes Metab 2019; 21: 1914-1924
  9. Kirk SFL, Ramos Salas X, Alberga AS, Russell-Mayhew S. Canadian Adult Obesity Clinical Practice Guidelines:  Reducing Weight Bias in Obesity Management, Practice and Policy. Available from: https://obesitycanada.ca/guidelines/weightbias. Last accessed: 22 November 2022
  10. Blüher M. Obesity: global epidemiology and pathogenesis. Nature Reviews Endocrinology 2019; 15:288–298


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