What is Obesity?
Obesity is a chronic disease - not just a lack of willpower.1-3
Our understanding of obesity is evolving, which is changing how we talk about, and treat it. When it comes to health, knowledge really is power.
Are you living with obesity?
BMI
Your doctor can help you understand the whole picture. While body mass index (BMI) is one way to assess it,8 your doctor may also consider factors9 like waist-to-height ratio and how excess weight affects your health, ability to function, and well-being.10 BMI is calculated by comparing your weight to your height and a high BMI can be an initial indicator of whether you should speak with you doctor.
To calculate your BMI, simply enter your height and weight into the BMI calculator below
You can then use the BMI range chart to see which category it falls within. The BMI categories are for those aged 20 and older alongside their definitions.8 It’s important to know that the BMI categories can differ depending on a person’s ethnicity.9 Remember, BMI is just one indicator - it's always best to talk with your doctor about it.
BMI CALCULATOR*
*The BMI calculator is not a diagnostic tool.8
Fill in your height and weight in order to receive your result.
BMI ranges8
< 18.5
If your BMI is less than 18.5kg/m2, it falls within the underweight range.
18.5 - 24.9
If your BMI is 18.5 to 24.9kg/m2, it falls within the healthy weight range.
25.0 - 29.9
If your BMI is 25.0 to 29.9kg/m2, it falls within the overweight range.
≥ 30.0
If your BMI is 30.0kg/m2 or higher, it falls within the obesity range.
Talk To Your Doctor
If you are concerned about your BMI results, it’s important to take steps to improve your overall health with your doctor.
Multiple factors influence obesity
We know how tough it can be to lose weight and keep weight off. Even with healthy eating and exercise, it can feel like you’re stuck in a cycle of losing and regaining weight.3,4 It makes you wonder if something more is at play. Thankfully, we now know there are a variety of factors that can contribute to obesity.1,2 Some of the key ones are listed below.
BIOLOGY
Obesity involves complex factors beyond your control, that may be linked to genetics.5,6 The brain and hormones play a major role in obesity, disrupting hunger and fullness signals.1,2,7 In people living with obesity this can lead to increased hunger, feeling less full, and changes in metabolism that can cause biological resistance to weight loss.1–3,7
LIFESTYLE
Consumption of food and level of physical activity can influence the risk of obesity.1,2 It is important to remember that lifestyle is one of the many factors that can contribute, but it’s often not the only one.1,2
ENVIRONMENT
Environmental factors that contributes to obesity include easy access to energy-dense, highly processed foods, and more urbanised areas coupled with sedentary (inactive) lifestyles resulting in less physical activity.1,2 Societal and cultural factors can also influence the environment we live in and how obesity is perceived and managed.2
Obesity affects your body, not just your weight
It is not just a number on a scale, it can impact many aspects of life.1,2 In fact, it is linked to over 200 complications.11,12
Greenway FL. Int J Obes (Lond). 2015;39:1188–96.
Rubino F, et al. Lancet Diabetes Endocrinol. 2025:13(3):221–62.
Hall KD, Kahan S. Med Clin North Am. 2018;102(1):183–97.
Apovian CM, et al. J Clin Endocrinol Metab.2015;100(2):342–62.
Bouchard C. Obesity. 2021;29(5):802–20.
Albuquerque D, et al. Br Med Bull. 2017;123:159–73.
Ochner CN, et al. Physiol Behav. 2013;120:106–13.
National Heart, Lung, and Blood Institute. Overweight and obesity: symptoms and diagnosis. Updated March 24, 2022. Available at: www.nhlbi.nih.gov/health/overweight-and-obesity/symptoms [Accessed February 2026].
Busetto L, et al. Nat Med. 2024;30(9):2395–9.
Stephenson J, et al. BMC Public Health. 2021;21(1):1990.
Albano G, et al. Neurosci Biobehav Rev. 2019;107:846–61.
Horn DB, et al. Postgrad Med. 2022;134(4):359–75.