BMI=the weight in kilograms divided by the square of the height in metres (kg/m2).7
≥18.5 and <25.0
≥25.0 and <30.0
Obesity, class I
≥30.0 and <35.0
Obesity, class II
≥35.0 and <40.0
Obesity, class III
Waist circumference can be used alongside BMI to assess a person’s risk for developing obesity-related complications. A larger waist circumference is associated with an increased risk of developing obesity-related complications and mortality.2
|Waist circumference cut-offs to identify increased relative risk for the development of obesity-related complications:2|
>102 cm (>40 in)
>88 cm (>35 in)
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
The Awareness, Care and Treatment in Obesity MaNagement – an International Observation (ACTION IO) Study is the first international study to investigate barriers to obesity management among people with obesity and healthcare professionals in 11 countries worldwide. A total of 14,502 people with obesity and 2,785 healthcare professionals completed the survey.13
Click here for more information on the ACTION IO Study.
Despite the recognition of obesity as a disease by many professional medical bodies, only approximately half of all people with obesity have discussed their weight with their healthcare professional in the last five years and only 36% of all people with obesity have received a formal diagnosis of obesity.13
Obesity is now so prevalent that it is one of the most significant contributors to ill health, replacing traditional public health concerns, such as undernutrition and infectious disease.7 An integrated approach, requiring actions from all sectors of society, will be necessary to achieve effective prevention and management of obesity.7
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
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.
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
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.
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
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
BP=blood pressure; CV=cardiovascular; DBP=diastolic blood pressure; HbA1c=glycated haemoglobin; HDL=high density lipoprotein; SBP=systolic blood pressure.
A weight loss of around 7% has shown a reduction in the incidence of type 2 diabetes by 58%16
Every 1 kg of weight loss can increase HDL levels by 0.009 mmol/L30
Achieving ≥5% weight loss can lead to an 80% risk reduction of sleep apnoea progression31
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
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 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
Benefits to weight related complications start with small amounts of weight loss, which can have long-standing health benefits. With increasing weight loss, the benefits in improving complications increase. Therefore, 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. 38
Below is an overview showing how much weight loss and maintenance of the weight loss is needed to improve some of the most prevalent weight-related complications. 38
Reprinted from Endocrine Practice, Vol 22, Garvey et al., “Treatment Goals Based on Diagnosis in the Medical Management of Patients with Obesity”, 1-203, Copyright (2016), with permission from the American Association of Clinical Endocrinologists. Available at: https://journals.aace.com/doi/pdf/10.4158/EP161365.GL
Despite, scientific literature stating that a weight loss of 5% or more can help to improve and reduce the risk of some obesity-related complications.16-18,41-44 41% of people with obesity would set themselves an ambitious weight loss target of 11-20% (overall mean weight loss target is 16%).13
Research shows that a high BMI is associated with a decreased life expectancy of up to 10 years.45
For every 5 kg/m2 BMI increment above the range of 22.5–25.0 kg/m2, there is a 30% increase in overall mortality.45
Adapted from Prospective Studies Collaboration. Body-mass index and cause-specific mortality in 900,000 adults: collaborative analyses of 57 prospective studies. Lancet. 2009;373(9669):1083–1096.
‡Data from male subjects.
People with obesity have a 55% increased risk of developing depression over time, whereas people with depression have a 58% increased risk of developing obesity.46
Several studies have found that the effect of weight stigma on people with obesity may lead to depression and a lower health-related quality of life.46
The higher the BMI, the greater the risk of impaired physical functioning, which may include limitations in mobility activities such as walking and dressing.47,48
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.
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
A review of 14 long-term studies showed that people with obesity regained weight after weight loss achieved by dieting.55
“…the high rate of relapse among people with obesity who have lost weight has a strong physiological basis and is not simply the result of the voluntary resumption of old habits.” 4
Study participants’ weight and diet statuses were assessed at baseline; their weight was then monitored for up to seven years after the diet ended. These data are from a review of 14 diet studies with long-term follow-ups.55
Adapted from Mann T, Tomiyama AJ, Westling E, Lew AM, Samuels B, Chatman J. Medicare's search for effective obesity treatments: diets are not the answer. Am Psychol. 2007;622(3):220–233.
81% of people with obesity have engaged in one or more serious weight loss attempts; however, only 11% were able to maintain a 5% weight loss for one year or more.13
Click here to explore our patient interaction tools to aid initiation or follow-up of dialogue with patients about their obesity management.
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.