According to the World Health Organization (WHO), obesity is characterized by “an abnormal or excessive accumulation of body fat which can be harmful to health.”

Basically, obesity results from consuming too many calories relative to energy expenditure over several years.

We must distinguish obesity from overweight, which is less important. Morbid obesity, on the other hand, is a very advanced form of obesity. It is said to be so damaging to health that it reduces life expectancy by 8 to 10 years.

Diagnosis of obesity

You cannot rely solely on a person’s weight to determine whether they are obese or overweight. Different measures are used to provide additional information and to predict the impact of obesity on health.

The body mass index (BMI)

According to the WHO, this is the most useful, albeit approximate, tool for measuring overweight and obesity in an adult population. This index is calculated by dividing the weight (kg) by the height squared (m2). We talk about being overweight when BMI is between 25 and 29.9; obesity when BMI is equal to or greater than 30; and morbid obesity if it is 40 or more. Healthy weight is a BMI between 18.5 and 25.

The main disadvantage of this measuring tool is that it does not give any information on the distribution of fat reserves. However, when fat is concentrated mainly in the belly region, the risk of diabetes and cardiovascular disease is higher than if it is concentrated in the hips and thighs, for example.

In addition, BMI does not distinguish between the mass of bones, muscles (muscle mass), and fat (body fat). Therefore, the BMI is imprecise for people with large bones or very muscular builds, such as athletes and bodybuilders;

The waistline

Often used as a supplement to BMI, it can detect excess fat in the abdomen. Abdominal obesity is considered when the waist circumference is greater than 88 cm (34.5 in) for women and 102 cm (40 in) for men. In this case, the health risks (diabetes, hypertension, dyslipidemia, cardiovascular disease, etc.) are considerably higher.

The waistline/hip circumference ratio

This measurement gives an even more precise idea of ​​the distribution of fat in the body. The ratio is considered high when the result is greater than 1 for men and greater than 0.85 for women.

Ongoign research

Researchers are working to develop new tools to measure excess fat. One of these, called the Body Fat Index or BFI, is based on measuring hip circumference and height. However, it has not yet been proven and is therefore not used medicinally at the moment.

To assess the existence of risk factors for disease, a blood test (especially the lipid profile) provides valuable information to the doctor.

Obesity in numbers

The proportion of obese people has increased over the past 30 years. According to the World Health Organization (WHO), the prevalence of obesity has grown to epidemic proportions globally. The increase in average weight is observed in all age groups, in all socio-economic groups.

  • Globally, 1.5 billion adults 20 years of age and over are overweight, and at least 500 million of them are obese. Developing countries are not spared;
  • In the United States, about a third of people aged 20 and over are obese and another third are overweight;
  • In Canada, according to the most recent data, 36% of adults are overweight (BMI> 25) and 25% are obese (BMI> 30) 5;
  • In France, nearly 15% of the adult population is obese, and about a third are overweight.

Causes of obesity

When we try to understand why obesity is so prevalent, we find that the causes are multiple and do not lie solely with the individual. The government, municipalities, schools, the agri-food sector, etc. also bear a share of responsibility in the creation of obesogenic environments.

The term obesogenic environment is used to describe a living environment that contributes to obesity:

  • accessibility to foods high in fat, salt and sugar, very high in calories and not very nutritious (junk food);
  • sedentary and stressful lifestyle;
  • living environment not very conducive to active transportation (walking, cycling).

This obesogenic environment has become the norm in several industrialized countries and is found in developing countries as people adopt a Western way of life.

People whose genetics make it easier to gain weight are more likely to fall victim to the obesogenic environment. However, genetic susceptibility alone cannot lead to obesity. For example, 80% of Pima Indians in Arizona today suffer from obesity. However, when they followed a traditional lifestyle, obesity was much rarer.

Consequences of obesity

Obesity can increase the risk of many chronic diseases. The health problems would start to manifest themselves after about 10 years of being overweight.

Significantly increased risks of:

  • type 2 diabetes (90% of people with this type of diabetes are overweight or obese);
  • hypertension;
  • gallstones and other gallbladder problems;
  • dyslipidemia (abnormal levels of lipids in the blood);
  • shortness of breath and sweating;
  • sleep apnea

Moderately increased risks of:

  • cardiovascular problems: coronary artery disease, cerebrovascular accidents (stroke), heart failure, cardiac arrhythmia;
  • osteoarthritis of the knee;
  • Gout

Slightly increased risks of:

  • certain cancers: hormone-dependent cancers (in women, cancer of the endometrium, of the breast, of the ovary, of the cervix; in men, prostate cancer) and cancers related to the digestive (cancer of the colon, of the gallbladder, of the pancreas, of the liver and of the kidney);
  • reduced fertility, in both sexes;
  • dementia, low back pain, phlebitis and gastroesophageal reflux disease.

How fat is distributed throughout the body, rather in the abdomen or hips, plays a major role in the development of disease. The accumulation of fat in the abdomen, typical of android obesity, is much riskier than the more even distribution (gynoid obesity). Men have on average twice as much abdominal fat as premenopausal women.

Worryingly, some of these chronic diseases, like type 2 diabetes, now appear in adolescence, given the growing number of young people who are overweight and obese.

Obese people have a poorer quality of life as they age and a shorter life expectancy than people who are at a healthy weight. Moreover, health professionals predict that today’s young people will be the first generation of children whose life expectancy will not exceed that of their parents, mainly because of the increasing frequency of obesity in children.

Finally, obesity can become a psychological burden. Some people will feel excluded from society because of the beauty standards established by the fashion industry and the media. When faced with difficulty losing excess weight, others will experience great distress or anxiety, which can lead to depression.

Symptoms of obesity

Obesity results in an excess of fatty tissue. This excess can be broken down in 2 different ways:

  • in the abdominal region, this is called android, visceral, or abdominal obesity;
  • the hips, thighs and periphery, known as gynoid obesity, peripheral, or subcutaneous.

For hormonal reasons, android obesity mostly affects men; and gynoid obesity, women.

People at risk

  • People who live in or immigrate to the United States. According to a study, 1 year after settling in the United States, 8% of immigrants become obese. After 15 years, 19% have become obese, which is close to the obesity rate of Americans of 22%. The most significant weight gain would occur after 10 years;
  • People whose hereditary background predisposes them to obesity.
  • Obesity depends above all on environmental factors (palatable foods with high energy density, sedentary lifestyle, stress), but also on genetic factors. The obesogenic environment in which we live is particularly harmful to individuals who are genetically predisposed to obesity. The predisposition to obesity depends on more than one gene (polygenic obesity), with monogenic forms of obesity (dependent on a single gene) being rare (about 5% of severe obesity).
  • The combination of an obesogenic background and a genetic predisposition is very likely to lead to the development of obesity.
  • Some ethnicities are more likely than others to gain weight. This would be the case for those who have had to survive major famines because their bodies have learned to “store” calories very efficiently. When these groups are exposed to a Western way of life, they are at greater risk for obesity (e.g. Pima Indians from Arizona, Aborigines from Australia, and immigrants from India and Pakistan) ;
  • As we age, we become less active and muscle mass tends to decrease, resulting in a slower metabolism. Calorie needs also decrease with age. If you don’t reduce your food intake, you gain weight;
  • People who live in urban areas. The prevalence of obesity is higher among urban populations compared to rural populations;
  • Certain illnesses can cause weight gain by making you inactive. Others will help with weight gain by lowering energy expenditure, but these are rare: hypothyroidism, Cushing’s disease (a problem with the adrenal glands) or a tumor of the hypothalamus;
  • People struggling with bulimia;
  • People who were overweight during childhood or adolescence;
  • Pregnancies can contribute to weight gain.

Individual factors that lead to weight gain and obesity

  • Eating behaviors. Eating large portions, eating a diet that frequently includes foods high in fat, salt or sugar, eating irregular meals, which encourages food compulsions. These behaviors are sometimes influenced by emotional states. This is the case if you eat to escape boredom, loneliness, stress, anxiety, etc., or if food becomes a way of rewarding yourself;
  • A sedentary lifestyle. Sedentary work and leisure (television, video games, the Internet, etc.) have become the norm. A study in England found that in the early 1990s, only 20% of men and 10% of women had a job requiring physical activity;
  • Stress. Weight gain often occurs during a period of adjustment or following a significant ordeal, for example major professional challenges, loss of employment, separation, bereavement, etc. The tendency to compensate by eating comfort foods is then stronger;
  • Deep distress. Eating compulsions may reflect temporary boredom, but sometimes they are a sign of great psychological distress. Eating then becomes a survival mechanism, to alleviate unbearable suffering and a state of being;
  • The family cultural heritage. Lifestyle habits – preparing and sharing meals, activities – are influenced by the family;
  • Lack of sleep can increase hunger;
  • Medicines can cause weight gain when taken for a long time, including certain antidepressants, antipsychotics, corticosteroids (by mouth or by injection) and beta blockers;
  • Drinking alcohol frequently can lead to weight gain by increasing calorie intake and stimulating hunger (hence alcoholic drinks served as an appetizer, to whet the appetite).

Factors and social changes that contribute to weight gain or obesity

  • A food industry that offers a multitude of foods high in calories, fat, salt and sugar. These foods are easily accessible, at any time of the day and at low cost. The colossal sums invested to promote “junk” foods to the public are also pointed out;
  • The majority of children’s food advertisements on television promote questionable or downright unhealthy foods. Studies show that advertisements greatly influence children’s food preferences, according to the Institute of Medicine of the National Academies in the United States;
  • Advertisements, as well as the media, which encourage thinness;
  • Due to the difficult work-family balance, a good number of parents resort more and more often to frozen meals or from restaurants. Meals are eaten less with the family. As a result, parents have less control over what their children eat and education about healthy eating is compromised;
  • Eating out more frequently;
  • The ever increasing portion sizes in restaurants and in the supermarket;
  • Automation of work and technological change, which make physical activity less and less necessary on a daily basis. Not only is the work sedentary, but many workers frequently experience psychological pressure and stress;
  • Urban planning that does not promote walking and physical activity;
  • The loss of a sense of security in neighborhoods, resulting in children playing less outdoors, using little walking or cycling to get to school, etc.

How to prevent obesity

Preventing obesity can begin, in a way, as soon as you start eating. Studies have shown that the risk of obesity is closely linked to eating behavior during childhood.

Already, from 7 months to 11 months, American infants consume 20% too many calories compared to their needs. One-third of American children under the age of 2 do not consume fruits and vegetables, and among those who do, French fries top the list.


Consuming weight loss products and submitting to a severe diet without changing your eating habits is certainly not a good solution. A healthy diet should be varied and include fresh fruits and vegetables. Eating well involves cooking your own meals, replacing certain ingredients, flavoring foods with herbs and spices, taming new cooking methods to use less fat, etc.

Some advice for parents

  • If you eat well, it will be much easier to get your children to do the same;
  • Eat meals with the family;
  • Be careful not to respond to the infant’s crying by systematically feeding him or her. Crying may express a need for affection or just a need for sucking. Many people meet their emotional needs with food: this behavior may have started very early in life;
  • Don’t always praise your child when they finish their bottle or their plate. Eating is normal, and not to please parents;
  • Avoid using food as a reward or punishment;
  • Let the child judge his or her own appetite. An infant’s appetite varies from day to day. If he or she is generally eating well and is not losing weight, there is no need to worry if he or she does not finish a meal every now and then. Don’t force the child to finish their plate. Thus, he or she will learn to listen to the signals of hunger and satiety;
  • Water is the perfect drink to quench thirst. Consumption of fruit juice, even natural, should be limited to 1 glass per day. Fruit juices are high in calories (many drinks and fruit punches contain as many as soft drinks), and do not satisfy hunger. Avoid adding sugar to yogurts, fruit purees, etc;
  • Vary the foods and the way you cook them. Diversify the sources of protein (fish, white meat, legumes, dairy products, etc.);
  • Little by little, introduce your child to new flavors.

Physical activity

Physical activity is an essential part of maintaining a healthy weight. Moving increases muscle mass and therefore energy needs. Get the kids moving, and move with them. Limit television and gaming time if necessary. A good way to be more active on a daily basis is to walk to the neighborhood shops when doing groceries and shopping.


Many studies indicate that sleeping well helps in better weight control. Lack of sleep may cause you to eat more to compensate for the reduced energy your body feels. In addition, it may stimulate the secretion of hormones that trigger appetite.

Stress management

Reducing the sources of stress or finding the tools to manage them better can make it less likely that you will try to compensate with food. In addition, stress often causes us to eat faster and more than necessary.

Be proactive

To make the environment less obesogenic, and therefore to make healthy choices easier to make, the participation of several social actors is necessary. Several health organizations have proposed a list of measures that authorities can implement in schools, workplaces, the agri-food sector, etc., to help fight the obesity epidemic.

  • Food policies in daycare and school settings;
  • Modification of the physical and social environment to promote a more active lifestyle;
  • Revision of the regulations on advertising aimed at children;
  • Regulation of the sale of weight loss products and services;
  • Renewed focus on research on obesity.

Treatment of obesity

The most effective approach to improving long-term health is personalized, multidisciplinary, and requires regular monitoring. The therapeutic approach should ideally include the services of the following professionals: a doctor, a dietitian, a kinesiologist, and a psychologist.

We must start with a health check established by a doctor. Consultations with other health professionals follow. It is better to bet on a follow-up over several years, even during the weight maintenance phase. Unfortunately, few clinics offer such support.

According to experts at the Mayo Clinic in the United States, a weight loss corresponding to 5% to 10% of body weight can significantly improve health. For example, for a person weighing 90 kilograms, or 200 pounds (and being obese according to their body mass index), this corresponds to a weight loss of 4 to 10 kilograms (10 to 20 pounds).

Weight loss diets: to be avoided

Most weight-loss diets are ineffective at long-term weight loss, in addition to being risky. Here are some possible consequences:

  • long-term weight gain: the calorie restriction imposed by diets is often untenable and generates intense physical and psychological stress. In a state of deprivation, appetite increases and energy expenditure decreases.
  • After analyzing 31 studies from the United States and Europe, researchers observed that there could be weight loss during the first 6 months of a diet. However, 2 to 5 years later, up to two-thirds of people regained the weight lost and even gained a few more pounds.
  • dietary imbalances: according to a report published by the French National Agency for Health Security, dieting without the advice of a specialist can lead to nutrient deficiencies or even excess.


With the help of a dietitian-nutritionist, it’s about finding a nutritional approach that suits the patient’s own tastes and lifestyle and learning to decipher his or her eating behaviors.

Physical activity

Increasing your energy expenditure goes a long way in losing weight and improving your overall health. It is safer to consult a kinesiologist before undertaking any physical activity. Together, you can choose a training program that is appropriate for your physical condition and interests.


Consulting a psychologist or psychotherapist can help you understand the origin of excess weight, change certain eating behaviors, better cope with stress and regain your self-esteem, etc.


Some prescription drugs can help with weight loss. They are reserved for people with significant risk factors for cardiovascular disease, diabetes, hypertension, etc. These drugs cause modest weight loss (2.6 kg to 4.8 kg). You have to keep taking them for the effect to last. In addition, they must be associated with a strict diet and have several contraindications.


Weight loss surgery most often involves reducing the size of the stomach, which can reduce food intake by about 40%. It is reserved for people who are morbidly obese, that is to say, those whose body mass index exceeds 40, and those whose BMI is higher than 35, and those who have a disease related to obesity.

Note. Liposuction is cosmetic surgery and should not be used for weight loss, according to experts.

Cassidy Perry

A certified dietician specializing in diabetes care, Cassidy has over a decade of experience working with diverse patient backgrounds. She writes health-related articles for the Scientific Origin.