Obesity is defined as an excess of body fat resulting in a significant increase in weight and which can have negative effects on the health and well-being of the individual. Since 1997, it has been recognized as a chronic disease by the World Health Organization (WHO). 

Prevalence of obesity

Today we can talk of a global epidemic attacking the youngest among us. In Canada, the obesity rate among children aged 6 to 17 has in fact gone from 6% in 1978 to 13% in 2014. Although stabilized, this percentage has not decreased over the past ten years, so nearly one in three Canadian children is currently overweight or obese. 

Globally, according to the WHO, more than 1.9 billion adults (or 26%) were overweight and, among them, there were 650 million obese (9%). 

These numbers have almost tripled since 1975! Similar findings in Quebec, where the prevalence of adult obesity has doubled over the past 25 years. In 2013, according to health authorities, it affected 20% of Quebec men and 16% of Quebec women. Despite a relative stabilization, the projections of the National Institute of Public Health of Quebec (INSPQ) are very worrying. By 2030, no less than one in four men and one in five women could be affected by this disease.

Social and human impact

Globally, overweight and obesity are now associated with more deaths than underweight caused by starvation or disease. This is an unprecedented situation that affects all high and middle-income countries like Canada. This mortality is explained by the fact that obesity is a complex risk factor for chronic diseases and is associated with a number of socio-economic determinants.

A scourge

In 2003, a study published in the Journal of the American Medical Association concluded that obese children have a quality of life so inferior to that of “normal” weight children that it is similar to that of those with cancer! Rejection, shame, vexations, recurring health problems and lack of self-confidence are their daily lot.

The problem worsens in adulthood when food deprivation and weight control become real obsessions. For the unlucky ones with morbid obesity, any move becomes a challenge and secondary illnesses significantly affect their quality of life. Even after bariatric surgery, an American study found that severely obese people are one and a half times more likely to attempt suicide than before surgery. Hence, the importance of good post-operative follow-up and support.

A public health challenge

Obesity is now a public health issue as important as smoking since it leads to an increase in coronary and cardiovascular diseases, several cancers, type 2 diabetes, and a number of other complications (joint problems, breathing difficulties, sleep disturbances, etc.). Research has shown that in 2011, the number of medical consultations for obese people was 13% higher than for people of normal weight and they were 94% more likely to spend the night in the hospital!

Significant economic consequences

Given the above, it is considered that obesity costs the Quebec government more than one and a half billion in health care per year, or one-tenth of the total cost of medical consultations and hospitalizations for Quebec adults. At the federal level, the Canadian Obesity Network estimates that the health costs related to this disease vary between 4.6 and 7.1 billion dollars per year.

The negative economic consequences do not end there, however. In companies, obesity also has a cost that translates into absenteeism, reduced productivity, injuries, and additional equipment costs.

A study by the firm Towers Watson identified obesity in 2014 as the third risk factor limiting the productivity of Canadian companies. In 2016, obesity fell to fourth place, behind unplanned absences, which was not mentioned in 2014, but it was of concern to 43% of Canadian respondents compared to 41% two years earlier. And this is makes sense since we know that the risk of absence from work would be nearly four times higher among obese Canadian men aged 18 to 34 than among their so-called “normal” weight colleagues.

A dangerous slope

In most cases, it is possible to reverse overweight and mild obesity thanks to simple lifestyle choices coupled with a good dose of willpower and perseverance. If left unchecked, however, mild obesity can worsen and lead to severe obesity and morbid obesity, which are the higher stages of the disease.

Severe or morbid obesity generally results from a conjunction of several factors, including some complex genetic abnormalities that science does not yet know how to fully control. Whether chronic or cyclical, it leads to major complications that considerably affect the quality of life, health, and life expectancy of patients. Faced with this alarming situation, we must not give up. From prevention to bariatric surgery, through self-regulating, regular exercise and consultation with psychologists or nutritionists, there are many avenues of solution that can help us better control the situation.

1 Source: Obésité : prévention et prise en charge de l’ épidémie mondiale, OMS, Genève, 1997.
2 Source: Poids santé chez les enfants au Canada, labo de données de l’Agence de la santé publique du Canada.
3 Source: Vers un Canada plus sain, rapport d’étape 2017, Réseau pancan. de santé publique.
4 Source: Obésité et surpoids, OMS, octobre 2017.
5 Source: Indicateurs synthèses sur l’obésité, INSPQ, modifié le 4 avril 2017.
6 Source: Embonpoint et obésité chez les enfants au Canada, Santé publique Canada, 2017.
7 Source: Health-Related Quality of Life of Severely Obese Children and Adolescents, JAMA, avril 2003.
8 Voir Chirurgie de l’obésité et risque de suicide : « Le suivi psychologique n’est pas toujours respecté », Sciences et Avenir, octobre 2015.
9 Source: Les conséquences économiques associées à l’obésité et à l’embonpoint au Québec : les coût liés à l’hospitalisation et aux consultations médicales, INSPQ, mise à jour 2016.
10 Voir Le poids économique de l’obésité, Radio Canada, octobre 2015.
12 Source: Enquête sur la santé dans les collectivités canadiennes (ESCC) citée dans Obésité et travail, Statistiques Canada, novembre 2015.

The rise in the rate of overweight and obesity in recent decades is undoubtedly explained by changes in our lifestyle. Bad eating habits, lack of physical exercise due to sedentary work, cars and television, stress and sleep disorders caused by work and technology are the most pointed culprits. But especially important genetic factors are also at play. In reality, obesity is a complex multifactor disease.

Genetic predisposition

There are many scientific studies that have demonstrated a clear statistical correlation between genetic inheritance and obesity. Thus, children born to “normal” or thin parents have less than a one in ten chances of developing the disease. If one of the parents is obese, the risk increases to four chances out of ten and it reaches eight chances out of ten if both parents are obese.

A few isolated cases are caused by a single defective gene altering the metabolism from birth and almost certainly leading to severe obesity. However, scientists have identified tens of genes that can induce a certain predisposition to the disease. These genetic particularities can combine and be aggravated by other lifestyle factors.

Overall, it is currently estimated that the role of heredity in obesity is around 40 to 50%. Gene therapies are being studied to cure some cases linked to a single genetic mutation. However, it is still far too early to fully understand and, even more so, be able to treat all the genetic factors associated with the most common cases.

Lack of exercise

Lack of exercise has a definite impact on the obesity rate, either in addition to genetic factors, or because of age or other situational factors. As soon as our body receives more energy than it consumes, it transforms the excess food into fat that it stores in adipose tissue. In order not to gain or lose weight, it is therefore necessary to maintain the balance between the energy that we absorb and that which we spend.

To maintain optimal health, adults aged 18 to 64 should get at least 150 minutes of moderate-to-vigorous intensity physical activity per week. Unfortunately, only 15% of Canadians meet or exceed this minimum quota.

Bad eating habits

Although famines continue to hit certain regions of the world hard, North America is going through an era of nutritional overabundance linked to the industrialization of the agri-food sector.

Encouraged by marketing and advertising, this overabundance translates into excessive overconsumption. 

  • The continuous snacking of salty and sweet products rich in simple carbohydrates and fat does not produce a satiety effect. Result: we want more.
  • The wide variety of food products available on the market also disrupts our satiety mechanism. Seduced by the appeal of new flavors, we no longer necessarily stop eating when our energy needs are met. Result: we eat too much.
  • The trend for “light” products is misleading. These foods low in fat but also exceptionally low in protein and loaded with sweeteners create a real “addiction”. Result: we always consume more!

Psychological and pathological factors

It is common for people suffering from obesity to have had a childhood or adolescence marked by socio-emotional deficiencies and psychic traumas leading, a few years later, to eating disorders. These cannot be permanently eliminated without addressing their psychological causes.

Finally, as we have previously seen, severe obesity is often linked to genetic factors, but also to complex pathologies such as metabolic or hormonal disorders. The combination of all these factors makes losing weight and maintaining it extremely difficult for people struggling with the acute stages of this disease.

The main measure used to assess the weight status of an individual is the body mass index (BMI). Defined by the World Health Organization (WHO). This number is calculated by dividing a person’s weight in kilograms by the square of their height in meters. Its unit is the kilogram per square meter.

For example, an adult person measuring 1.75 m (about 5′ 9″) and weighing 72 kilos (165 pounds) will have a BMI of 23.51 kg/m2 calculated as follows: 72 /72 (1.75)2 = 7272 /72 3.0625 = 23.51

Here is a calculator to easily calculate BMI using weight and height measurements of the metric or imperial system: go to this site.

In a nutshell

Although medicine knows how to better treat the common consequences of overweight and mild obesity than before, it is important to monitor your weight and, in the event of a significant increase, to consult your doctor. Better nutrition, a little physical exercise or even adequate psychological support can improve the quality of life while avoiding sliding into morbid obesity and its dire consequences.

Body Mass Index (BMI) Classification

The following table gives a simplified overview of the risks associated, in theory, with different body mass index values:


Classification Subclass BMI Health Risk
Extreme thinness < 16 High
Thinness 16 – 18,5 To be Monitored
Normal weight 18,50 – 25 Weak
Overweight 25 – 30 To be Monitored
Obesity Class I 30 – 35 High
Severe obesity Class II 35 – 40 Very High
Morbid obesity Class III > 40,00 Excessively High

The Institut de santé publique du Québec has published a detailed weight table (PDF, 88 Ko) allowing you to determine BMI from weight and height, but also to see immediately the weight to lose, or to gain, if underweight, in order to reach the healthy weight zone.

BMI is not an absolute indicator

  • It is not applicable to children or pregnant women.
  • Some individuals with above-average bone or muscle mass will be in good health despite a BMI theoretically corresponding to a state of overweight or obesity.
  • Some populations also reach the obesity threshold with a BMI lower by several points. This is particularly the case in China, Japan, and Asia-Pacific.
  • Finally, other measurements such as waist circumference and hip circumference provide additional indications that allow for a better assessment of the risks associated with a high BMI.

Overweight and mild obesity

In January 2013, a medical article published by a team of American researchers spoke to the scientific community and public opinion. This synthesis of 97 studies involving 3 million individuals in the world concluded that a slight overweight – even a slight obesity – confers a better life expectancy than a weight considered normal. The study did, however, confirm the increased mortality associated with more advanced stages of obesity.

What is important to remember from this study is that being overweight on its own does not lead to harmful consequences for physical health. It would even be preferable to a state of thinness or anorexia resulting in more damaging consequences. We should not be prejudiced against overweight people or discriminate against them, whether on the street, at school, in sports or at work. They can be, indeed, in perfect health and very well in their skin.

1 Read BMI Classification, WHO site visited March 3, 2018
2 Source: Study on optimal cut‐off points of body mass index and waist circumference in Chinese adults, Asia Pacific Journal of Clinical Nutrition, January, 2003.
3Source: Criteria and classification of obesity in Japan and Asia‐Oceania, Asia Pacific Journal of Clinical Nutrition, January, 2003.
4Source: Association of All-Cause Mortality With Overweight and Obesity Using Standard Body Mass Index Categories, Journal of the Medical American Association, quoted by une dépêche de l’AFP February 2nd, 2013.

Type I Obesity

With a BMI between 30 and 35, one faces a substantial risk of developing health problems. It is necessary to be followed by a doctor and to closely monitor your lifestyle in order to lose weight or, at the very least, to avoid slipping into a more advanced state of obesity.

There is no shortage of risk factors that can aggravate the situation. For example, stress caused by misfortune, family breakdown, bereavement or job loss is often a determining factor in the transition from class I to class II. A major change in lifestyle can be too — a change in diet caused by moving, for example, or quitting smoking without adequate mitigation measures. Finally, taking certain medications can also have a side effect of rapid and excessive weight gain that will be exceedingly difficult to reverse later.

Type II Obesity

With a BMI between 35 and 40, we enter the field of severe obesity, with an overweight of one hundred pounds or more. In Quebec, the number of people exceeding this threshold is estimated at 3% of the population (i.e., more than 200,000 people). Medical follow-up is essential in order to reduce and even preferably eliminate this excessive fat mass threatening our balance, our health and perhaps even, in the long term, our survival. The family, social and professional environment also has a critical role to play in supporting, encouraging, and accompanying.

Here again, significant work on factors related to lifestyle (nutrition, exercise, and psychological support) will be at the heart of the therapeutic course in order to reduce weight by at least 10%. The ultimate goal is to change one’s behavior in order to regain control and reverse the trend of being overweight.

However, some patients have metabolic complications that substantially increase the likelihood of type 2 diabetes and cardiovascular disease. In this case, the risks associated with these complications may justify the use of bariatric surgery, more or less urgently, depending on the patient’s condition.

Type III Obesity

With a BMI equal to or greater than 40, one is in the range of severe obesity, often called morbid obesity, which means “related to the disease”. Indeed, the list of high-risk complications associated with it, is long:

  • Type 2 diabetes and abnormal lipidemia.
  • Hypertension and cardiovascular diseases.
  • Problems related to the liver, pancreas, and gallbladder.
  • Musculoskeletal problems related to the joints.
  • Problems related to the reproductive system (menstruation, infertility, impotence).
  • Obstructive sleep apnea.
  • Certain types of cancer, in particular digestive or hormone dependent. 

The disease is then considered irreversible and bariatric surgery is generally the only possible option to minimize the risks and restore a good quality of life. Exercise no longer allows you to lose weight, but the bariatric course requires good behavioral and nutritional preparation.

1 Source: Hôpital du Sacré-Coeur de Montréal.
2 To find more on the differences between severe obesity and morbid obesity Banque de dépannage linguistique of the OQLF.

3 Source: Hôpital du Sacré-Coeur de Montréal.
4 Voir 11 types de cancer corrélés au surpoids et l’obésité?, Sciences et Avenir, avril 2017.
5 Source to not quote: obesite-severe-lexercice-physique-ny-peut-rien-ou-presque, Le Soleil, juin 2014.