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Obesity Explained

The World Health Organization (WHO) defines obesity as “abnormal or excessive fat accumulation that presents a risk to health”. The most common way we measure obesity is by using a calculation known as BMI (body mass index).

Body Mass Index (BMI)

  • Body size can be measured by ‘Body Mass Index’ or BMI. BMI is calculated using height measured in meters and weight measured in kilograms, using the formula:
  • BMI = Weight (kg)/[ Height (m) ] 2
Check your Body Mass Index
What is your weight?
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What is your height?
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You Body Mass Index(BMI) is:
You are

Your BMI Result indicates

  • Below 18.5 - UNDERWEIGHT
  • 18.5 - 24.9 - HEALTHY
  • 25 - 29.9 - OVERWEIGHT
  • 30 - 34.9 - CLASS 1 OBESITY
  • 35 - 39.9 - CLASS 2 SEVERE OBESITY
  • 40 and Above - CLASS 3 MORBID OBESITY
BMI (Kg/m2)Classification
< 20Underweight
20 – 24.920 – 24.9
25 – 29.9Overweight
30 – 34.9Obese
35 – 39.935 – 39.9
40 – 49.9Morbidly Obese
≥ 50Super Obese

A body mass index (BMI) greater than 30 is considered obese. It’s important to note that BMI is not a perfect tool. It does not consider age or sex and does not differentiate between muscle and fat tissue. Therefore, a fit person with a lot of muscle mass may have a high BMI. As such BMI in isolation may not be a reliable indicator of eligibility for bariatric surgery.

Using BMI as a tool in 2016, it was thought that more than 1.9 billion adults globally were overweight and over 650 million adults were obese.

There are many many factors which contribute to obesity including modern living, family history, genetics and an energy imbalance (consuming more calories than are used).

Obesity related health conditions

Elevated BMI is considered a major contributing factor for the following conditions:

  • Heart disease including high blood pressure and stroke
  • Respiratory disease including obstructive sleep apnoea
  • Diabetes
  • Disorders of the musculoskeletal systems including osteoarthritis
  • Some cancers including endometrial, breast, ovarian, prostate, kidney and colon
  • Infertility and pregnancy complications

The higher the BMI, the greater the risk of the above disorders. Obesity can also impact negatively on mental health, self esteem and an overall ability to participate in and enjoy life.

Permanent changes to diet and lifestyle such as limiting energy intake from total fats and sugars and engaging in regular exercise is the first line treatment for obesity. Prescription appetite suppressant medication may also be considered. The higher the BMI the more difficult it can be to maintain any weight loss achieved long term with diet and exercise alone.

Surgery as a tool to assist with weight loss

Where lifestyle changes have been unable to achieve or maintain weight loss and a person's health is at risk, surgical options may be considered. We encourage careful consideration and discussion with your General Practitioner, any specialist health care provider you might have as well as with a trusted support person and potential surgeon before deciding if surgery is right for you.

You may be a candidate for weight loss surgery if;

  • You have been unsuccessful maintaining or achieving weight loss in the past
  • Your excess weight is limiting and affecting your ability to live a fulfilling, active and happy life, including your ability to socialises and exercise
  • Excess weight is impacting your health and other medical issues. In this situation patients often state their general practitioner or physician wants them to lose weight.
  • You are prepared to change your eating and lifestyle behaviours
  • You are older than 18 years of age
  • Your BMI is greater than 30kg/m2

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