BMI=the weight in kilograms divided by the square of the height in metres (kg/m2).
≥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 risk threshold:
Country or ethnic group
|Europid, Eastern Mediterranean, Middle Eastern or Sub-Saharan African|
|South Asian, Chinese or South and Central American|
"Obesity is a chronic and often progressive condition not unlike diabetes or hypertension."7
TOS (The Obesity Society):
It is the official position of The Obesity Society that obesity should be declared a disease.8
AACE (American Association of Clinical Endocrinologists):
"[Obesity] must be viewed as a chronic disorder that essentially requires perpetual care, support, and follow-up."9
CMA (Canadian Medical Association):
"It is important for health care providers to recognize obesity as a disease so preventive measures can be put in place..."10
WOF (World Obesity Federation):
The World Obesity Federation takes the position that obesity is a chronic, relapsing, progressive disease process and emphasises the need for immediate action and the prevention and control of this global epidemic.11
Obesity is one of the most significant contributors to ill health, replacing traditional public health concerns, such as undernutrition and infectious disease.13 An integrated approach, requiring actions from all sectors of society, will be necessary to achieve effective prevention and management of obesity.13
The global prevalence of obesity has nearly tripled since 1975. In 2016, more than 1.9 billion adults aged ≥18 were overweight. In the same year, 39% of adults aged ≥18 were living with overweight, and 13% were living with obesity.14
Obesity is associated with multiple comorbidities.19
Compared to a person with overweight, class I obesity is associated with a:20
Canadians with obstructive sleep apnea are more likely to have diabetes, hypertension, heart disease and mood disorders.25
Globally, cardiovascular disease is the leading cause of mortality in people with obesity.26
Obesity was also responsible for high costs associated with its
Risk of mortality is significantly increased and quality of life is significantly decreased due to obesity.
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.33
Several studies have found that the effect of weight stigma on people with obesity may increase vulnerability to depression, low self-esteem, poor body image, maladaptive eating behaviours and exercise avoidance.33
BP, blood pressure; CV, cardiovascular; DBP, diastolic blood pressure; A1C, 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%35†
Every 1 kg of weight loss can decrease LDL levels by 8%36
Achieving 5–10% weight loss can lead to a 30% reduction of sleep apnea symptoms24‡
The higher the BMI, the greater the risk of impaired physical functioning, which may include limitations in mobility activities such as walking and dressing.37
Obesity has a negative impact on physical functioning compared with normal weight (BMI 18.5–24.9 kg/m2)38
Science has discovered that physiological responses to weight loss trigger weight regain.
Weight loss in people living with obesity has been shown to cause changes in appetite hormones that increase hunger and the desire to eat for at least 1 year.39
Multiple hormones, such as ghrelin, GLP-1, and leptin, play an important role in regulating appetite.2
Want to learn more about the science behind obesity? View our Rethinking Obesity video.
A review of 14 long-term studies showed that participants regained weight after weight loss achieved by dieting.43
“…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."39
Behavioural interventions including diet, exercise, and cognitive-behavioural therapy are recommended as the first-line treatment option for people living with overweight or obesity to achieve clinically important weight loss and reduce obesity-related symptoms.19 Other treatment options such as pharmacotherapy and bariatric surgery should not be considered until behavioural interventions have been unsuccessful.19
The ACTION (Awareness, Care and Treatment of Obesity MaNagement) Study is the first Canada-wide study that investigated the perceptions, attitudes, and perceived barriers to obesity management among Canadian people living with obesity (PwO), healthcare professionals (HCPs), and employers. The study was conducted through an online survey between August and October of 2017. The findings of this study highlight the misunderstanding and communication gaps that exist between these groups.44
The majority of the 2545 survey respondents* agreed with the statement that “obesity is a chronic medical condition”.44
74% of PwO reported that they believe obesity has a large impact on overall health.
81% of PwO agreed that it would be beneficial to their health to lose 5–10% of their body weight.
Selected outcomes of the ACTION Study can be grouped into the following topics:44
The general group of PwO reported engaging in several weight loss attempts.44
The most highly utilized methods for weight loss reported by PwO were:44*
Guidelines suggest that some PwO may face challenges that can prevent them from maintaining weight loss achieved through diet and exercise.19
The results of the ACTION Study indicated that most people living with obesity (74%) considered weight loss to be completely their own responsibility.
The median age at which PwO reported first struggling with excess weight was 28 years, while they reported first discussing weight with their HCP at a median age of 39 years.
These findings are aligned with the Canadian Obesity Guidelines which identify that PwO may be reluctant to seek medical attention, which may pose a barrier to adequate obesity management.19
Many PwO (52%) indicated that they had not received a formal diagnosis of obesity.44
Although 72% of HCPs reported discussing weight with their patients who are in need of weight management, only 54% of PwO reported that they have had such discussions in the previous 5 years.
The Canadian Obesity Guidelines recognizes that inadequate education and the lack of training programs available for physicians act as barriers to the medical management of obesity.19
A gap in the patient-provider dialogue was identified, whereby HCPs reported having discussions about weight management with 72% of their patients, but only 54% of PwO reported having these discussions in the past 5 years.44
A delay of more than 10 years was reported from the time that PwO first started struggling with excess weight to the time they first discussed weight with their HCP.
Only 28% of PwO who reported having a discussion about weight with their HCP said that a weight-related follow-up appointment or call was scheduled.
PwO who reported success in losing weight engaged in discussions with their HCPs earlier than those who had no current weight loss success (median: 5 vs. 12 years).
A lack of dialogue about weight management between PwO and HCPs, and few follow-up appointments may present a challenge to obesity management.
PwO and employers had differing perceptions of the benefit of employer wellness offerings.44
Employers reported the following weight management benefits offered by their companies:
The value of wellness programs offered by employers were perceived differently by employers and PwO.
49% of employers believe that wellness programs contribute “significantly” or “a lot” to successful weight loss, whereas only 12% of PwO agreed with these statements.
Perceived reasons for non-participation in employer wellness programs differed between employers and PwO:
Skewed perceptions of the value of wellness programs may present a challenge to effective obesity management.
Obesity should be treated and managed holistically and as a serious chronic disease.9,45
Behavioural and lifestyle interventions:
For obesity, this should include diet, exercise, and behavioural modification.43 Healthy eating, physical activity, and cognitive behaviour therapy should be first-line interventions in all individuals with a BMI ≥25 kg/m2 and they must be part of any weight loss intervention.19 However, behavioural interventions may not always be sufficient to maintain weight loss and some people living with obesity may require a combination of treatments that includes pharmacotherapy and/or bariatric surgery to help manage their weight.43
For obesity, pharmacotherapy can be considered if lifestyle interventions do not provide sufficient clinical benefit for individuals with a BMI of ≥30 kg/m2, or ≥27 kg/m2 with other comorbidities.19 Pharmacotherapy should be used as an adjunct to lifestyle modifications and considered if a patient has not lost 0.5 kg (1 lb) per week by 3–6 months after lifestyle changes.19
Is the third-line intervention for obesity management, which is recommended in individuals with a BMI ≥40 kg/m2, or ≥35 kg/m2 with comorbidities.19 Bariatric surgery can be malabsorptive or restrictive and requires lifelong medical monitoring.19,46
Guidelines for comprehensive medical care of patients with obesity and overweight according to BMI stage.
Adapted from Lau DCW, et al. (2007).
* Body mass index (BMI) and waist circumference cut-off points are different for some ethnic groups; refer to Table 3 of Lau DCW, et al. (2007) for ethnic-specific waist circumference cut-off points.
† Lifestyle modification program consisting of nutrition, physical activity, and cognitive-behaviour therapy.
‡ Adjunct to lifestyle modification; consider if patient has not lost 0.5 kg (1 lb) per week by 3–6 months after lifestyle changes.