What is Obesity?

Obesity is a chronic disease.1
 
Obesity is increasingly recognized as a chronic disease by many medical organizations, including the World Health Organization (WHO)1 and the American Medical Association (AMA)2 . Obesity is a chronic complex disease defined by excessive fat deposits that can impair health1,2 .

Obesity can stem from a complex combination of factors, including genetics, environment, diet, lifestyle, and social and cultural circumstances.3,4-7

Over the last decade, studies have shown that genetics contributes to body weight or BMI.4,5 For people living with overweight or obesity, it’s estimated that genetics can account for 50-80% of variability in body weight.4 The estimated contribution of genetics on variability in body weight for people who are not obese, or overweight is only 30-35%.4

However, it’s important to remember that genetics by itself rarely has the power to determine a person’s anatomy or their behaviour. It’s the interaction between genes and environment which can influence and activate weight gain.5
Just like many other long-term diseases, obesity has a significant impact on the person living with it and on the people around them.3,6,7

Living with obesity can lead to physical limitations, impact mental health, and is linked to over 200 health complications.7,8 People living with obesity can feel stuck after unsuccessful weight loss attempts due to factors beyond their control or can find themselves in a cycle of weight loss and regain.9

When trying to sustain weight loss, biological resistance may result in increased hunger, feeling less full, and changes in metabolism - these processes can work against your weight loss efforts.10

When you understand more about why it can be difficult to lose weight3,11 you and your healthcare provider can start to address the underlying causes of obesity and help you take control of your disease.

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What is Obesity?

Obesity is a chronic disease.1
 
Obesity is increasingly recognized as a chronic disease by many medical organizations, including the World Health Organization (WHO)1 and the American Medical Association (AMA)2 . Obesity is a chronic complex disease defined by excessive fat deposits that can impair health1,2 .

Obesity can stem from a complex combination of factors, including genetics, environment, diet, lifestyle, and social and cultural circumstances.3,4-7

Over the last decade, studies have shown that genetics contributes to body weight or BMI.4,5 For people living with overweight or obesity, it’s estimated that genetics can account for 50-80% of variability in body weight.4 The estimated contribution of genetics on variability in body weight for people who are not obese, or overweight is only 30-35%.4

However, it’s important to remember that genetics by itself rarely has the power to determine a person’s anatomy or their behaviour. It’s the interaction between genes and environment which can influence and activate weight gain.5
Just like many other long-term diseases, obesity has a significant impact on the person living with it and on the people around them.3,6,7

Living with obesity can lead to physical limitations, impact mental health, and is linked to over 200 health complications.7,8 People living with obesity can feel stuck after unsuccessful weight loss attempts due to factors beyond their control or can find themselves in a cycle of weight loss and regain.9

When trying to sustain weight loss, biological resistance may result in increased hunger, feeling less full, and changes in metabolism - these processes can work against your weight loss efforts.10

When you understand more about why it can be difficult to lose weight3,11 you and your healthcare provider can start to address the underlying causes of obesity and help you take control of your disease.

Are you living with obesity?

Body Mass Index (BMI) and
obesity

There are different considerations when defining obesity—it is more complicated than just a number on a scale.12 Obesity is a chronic disease and while BMI can be used to categorise obesity, your doctor may consider additional factors.13 Some of these factors include the measurement of waist-to-height ratio and the effect that excess weight has on your health or quality of life whether that be medically, functionally, or psychologically.14 BMI is calculated by comparing your weight to your height and can be an initial indicator on whether you should speak with your doctor.

Enter your height and weight to
calculate your BMI.

Use the chart below to see the BMI categories for those aged 20 and older and their definitions.15 It’s important to note that the BMI categories can differ depending on a person’s ethnicity. 13 Remember, your BMI is just one indicator for obesity—it is always best to talk with your doctor about it.

BMI CALCULATOR

Fill in your height and weight in order to receive your result.

If you are concerned about your BMI results, consult your doctor.

BMI ranges15

≤18.5

If your BMI is less than 18.5kg/m2 , it falls within the underweight range.

18.5 - 22.9

If your BMI is 18.5 to 22.9kg/m2 , it falls within the healthy weight range.

23 - 27.4

If your BMI is 23 to 27.4kg/m2 , it falls within the Overweight range.

27.5 - 32.4

If your BMI is 27.5 to 32.4kg/m2 , it falls within the Obesity Class I range.

32.5 - 37.4

If your BMI is 32.5 to 37.4kg/m2 , it falls within the Obesity Class II range.

≥ 37.5

If your BMI is 37.5kg/m2  or higher, it falls within the Obesity Class III range.

ReferencesExpand Icon
  3. Greenway FL. Physiological adaptations to weight loss and factors favouring weight regain. Int J Obes (Lond). 2015;39(8):1188–1196.
  4. Bouchard C. Genetics of Obesity: What We Have Learned Over Decades of Research. Obesity 2021; 29(5):802–820.
  5. Albuquerque D, Nóbrega C, Manco L, and Padez C. The contribution of genetics and environment to obesity. British Medical Bulletin 2017; 123:159–173.
  6. Eunice Kennedy Shriver National Institute of Child Health and Human Development. What causes obesity & overweight? Reviewed July 28, 2021. Available at: https://www.nichd.nih.gov/health/topics/obesity/conditioninfo/cause [Accessed January 2025].
  7. Albano G, Rowlands K, Baciadonna L, Coco GL, Cardi V. Interpersonal difficulties in obesity: a systematic review and meta-analysis to inform a rejection sensitivity-based model. Neurosci BENEFI.
  8. Horn SB, Almandoz JP, Look M. What is clinically relevant weight loss for your patients and how can it be achieved? A narrative review. Postgrad Med. 2022;134(4):359–375.
  9. Hall KD, Kahan S. Maintenance of lost weight and long-term management of obesity. Med Clin North Am. 2018;102(1):183–197.
  10. Ochner CN, Barrios DM, Lee CD, Pi-Sunyer FX. Biological mechanisms that promote weight regain following weight loss in obese humans. Physiol Behav. 2013;120:106–113.
  11. MacLean PS, Bergouignan A, Cornier MA, Jackman MR. Biology's response to dieting: the impetus for weight regain. Am J Physiol Regul Integr Comp Physiol. 2011;301(3):R581–R600.
  12. National Heart, Lung, and Blood Institute. Overweight and obesity: symptoms and diagnosis. Updated March 24, 2022. Available at: https://www.nhlbi.nih.gov/health/overweight-and-obesity/symptoms [Accessed January 2025].
  13. Busetto L, Dicker D, Frühbeck G, et al. A new framework for the diagnosis, staging and management of obesity in adults. Nat Med. E-pub July 5, 2024. doi:10.1038/s41591-024-03095-3.
  14. Stephenson J, Smith CM, Kearns B, Haywood A, Bissell P. The association between obesity and quality of life: a retrospective analysis of a large-scale population-based cohort study. BMC Public Health. 2021;21(1):1990.
  15. Malaysia Health Technology Assessment Section (MaHTAS). Malaysian Clinical Practice Guidelines for the Management of Obesity, 2nd edition (2023). Available at: https://mems.my/cpg-management-of-obesity [Accessed August 2025].