

Obesity is classified in three ways according to WHO:

  • obese class I: BMI 30–34.9
  • obese class II: BMI 35–39.9
  • obese class III: BMI 40 or higher

In addition to BMI, waist circumference should also be considered to identify health risk.

Causes of obesity in adulthood

Obesity in Canada is on the rise. In the last decade, the number of obese Canadians has increased by 17.5%. Overall, 26% of men and 23% of women are obese. Factors that can increase your risk of obesity include:

  • diet: Dietary choices such as low consumption of fruits and vegetable and larger portion sizes and behaviour such as eating while watching television and drinking sweetened beverages as a part of meals or between meals have been associated with an increased risk of obesity.
  • physical activity: A sedentary lifestyle is likely one of the main reasons for the increase in obesity, especially among people in affluent societies.
  • genetics: Research suggests that on average, genetics influence about 33% of body weight, but it may be more or less in a particular person.
  • socioeconomics: Social status plays a big part in weight, especially among women. Why this occurs is not fully understood, but women in higher socioeconomic groups tend to have more time and resources for dieting and exercise.
  • community-level factors: People who live in communities with a lack of access to grocery stores and physical activity facilities have an increased risk of obesity.
  • psychological: Two abnormal eating patterns, binge eating and night eating, may be triggered by stress, emotional upset, and a negative body image. Binge eating is similar to bulimia except that the binges are not followed by self-induced vomiting – meaning more calories are consumed.
  • developmental: An increase in the size and/or number of fat cells adds to the amount of fat stored in the body. Obese people, particularly those who have been obese since childhood, may have 5 times as many fat cells as people with normal weight.
  • drugs: A number of commonly used drugs cause weight gain, including corticosteroids such as prednisones and antidepressants, as well as other drugs used to treat psychiatric disorders.
Written and reviewed by the MediResource Clinical Team