Samuel's BMI is 40

What is obesity?

Obesity is a complex and multifactorial disease that is influenced by physiological, psychological, environmental, socio-economic and genetic factors.¹ ²

Click on each factor above to find out more.

Is obesity a disease?

European Association for the Study of Obesity (EASO)

“A progressive disease, impacting severely on individuals and society alike, it is widely acknowledged that obesity is the gateway to many other disease areas.” 10

The Obesity Society (TOS)

It is the official position of The Obesity Society that obesity should be declared a disease.9

American Medical Association (AMA)

"Recognizing obesity as a disease will help change the way medical community tackles this complex issue that affects approximately one in three Americans." 11

American Association of Clinical Endocrinologists (AACE)

"...obesity is a primary disease, and the full force of our medical knowledge should be brought to bear on the prevention and treatment of obesity as a primary disease entitity." 8

World Obesity Federation (WOF)


The World Obesity Federation takes the position that obesity is a chronic, relapsing, progressive disease process and emphasises the need for intermediate action and the prevention and control of this global epidemic.12


Acknowledgement of obesity as a disease could improve the overall management of obesity.14

Common complications associated with obesity

Obesity is much more than just excess weight. It is associated with over 200 complications affecting various organ systems and medical specialities. 15

When it comes to managing your patients with obesity, it's important to communicate that even small amounts of weight loss can significantly reduce the risk of developing some of these complications.

While some complications are more sensitive to weight loss than others, a weight loss of as little as 5% has significant health benefits, and a weight loss of 10% or more can further enhance these benefits and provide additional weight-loss related improvements to health.16-22

Below are some common complications of obesity, which show improvements following weight loss.


Cardiovascular disease – hypertension, heart failure and dyslipidaemia

Association with obesity

Cardiovascular disease is the leading cause of mortality in people with obesity. 23 There is clear association between BMI and hypertension, heart failure, cardiovascular mortality and dyslipidaemia. For example, the prevalence of hypertension increases with increasing BMI, 24 whereby people with a BMI of 25.0–29.9 kg/m2 are three times more likely to develop hypertension than individuals with a normal range BMI. 24  

The benefits of weight loss

For people with obesity and stage 1 hypertension, the first ACC/AHA recommendation is to treat patients by reducing weight through lifestyle modifications, pharmacological treatment and/or bariatric surgery; and not initiating antihypertensive medications. 25 These findings indicate that weight loss is important for the prevention as well as the initial treatment of hypertension.

Pre diabetes and type 2 diabetes

Association with obesity

Men and women living with obesity are nearly seven and >12 times more likely to develop type 2 diabetes than individuals without obesity respectively. 26

The benefits of weight loss

For individuals with pre diabetes, treatment through weight loss not only reduces the risk of developing diabetes, 16 but can also take diabetes into remission. 27 Weight loss studies including the use of pharmacotherapy show that with some newer anti-obesity medications, the risk of developing diabetes can be reduced by as much as 80% over three years. 28 Importantly, in patients with obesity and pre diabetes, even 10 years after initial weight loss and despite weight regain there is a significant reduction in the risk of developing type 2 diabetes compared to those individuals who didn’t lose any weight. 29


Association with obesity

Men and women with obesity are over four and two times more likely to develop osteoarthritis than someone without obesity, respectively. 26 Weight loss is the first recommendation in any guideline for knee osteoarthritis. 32  

The benefits of weight loss

Weight has been strongly associated with prevalence of knee osteoarthritis, with 15% increase in risk per unit increase in BMI. 19 In these cases, weight loss is recommended as part of management and also leads to symptom relief and improves function, functional status and reduces pain. 20

Association with obesity

Prevalence of asthma has been found to increase with BMI, with one unit of increased BMI associated with 6% increase in asthma risk in women, and 3% in men. 33  

The benefits of weight loss

For people with asthma, weight loss has been proven to carry benefits such as improving quality of life, pulmonary function and asthma disease control. 34  

Polycystic ovary syndrome (PCOS) and infertility

Association with obesity

The pathophysiology of PCOS is complex and remains largely unclear, however the condition has been found to be intricately linked with obesity. Between 60% and 80% of women with PCOS have obesity, and it is considered to contribute and exacerbate complications of PCOS, 35 including developing insulin resistance and pre diabetes/diabetes, 36 heart disease, 37 and fertility problems or infertility. 36

The benefits of weight loss

Weight loss is the primary recommended treatment for PCOS, 38 improving clinical features and long-term metabolic health in women with PCOS. Some of these improvements include lowered insulin levels, 39 decreased insulin resistance, 36 decreased androgen levels 40 and risk factors for cardiovascular disease and type 2 diabetes. 37 Importantly, menstrual cyclicity, ovulation and fertility have been shown to improve following weight loss. 36  

Why is it hard to lose weight and keep it off?

Physiological responses to weight loss favour weight regain.4,49-52

Weight loss alters the body's homeostatic system,53 which controls appetite, energy intake and energy expenditure,54 causing the body to increase hunger and lower the metabolic rate.53

Want to learn more about the science behind obesity? View our obesity mode of disease video.

metabolic adaptations to weight loss

Weight loss in people with obesity causes changes in appetite hormones that increase hunger and the desire to eat for at least 1 year.4



Click here to explore our patient interaction tools to aid initiation or follow-up of dialogue with patients about their obesity management.

Science behind obesity additional materials

Explore the science behind obesity interactive infographic to learn more about the factors inside and outside the body that affect a person’s likelihood of developing obesity.