What is Childhood Obesity?

Everyone has a body shape that is just right for him or her but sometimes we can store excessive body fat. Obesity is defined as abnormal or excessive fat accumulation that may impair health. Childhood obesity is a medical condition that affects children and teenagers.

A healthy weight trajectory is where height and weight change proportionally together as children develop. When children are off the healthy weight trajectory, their weight gain is disproportionate to their change in height, meaning an excessive accumulation of body fat that can negatively impact his or her health. If a child or adult stores too much fat they can be classified as overweight or obese. A sign of childhood obesity is a weight well above the average for a child’s height and age.

A child or youth is classified as either being overweight or obese based on their Body Mass Index (BMI). The BMI is calculated from a person’s weight in kilograms and height in meters. You can visit the Dietitians of Canada website to calculate your child’s BMI and to see how it is classified.

If left unchecked, research shows that overweight or obese children are more likely to become obese adults and thus more likely to experience compromised health due to chronic disease, contributing to growing personal and health care costs.

Which children are at risk of becoming overweight or obese?

Most childhood unhealthy weights are caused by children eating too much of the wrong foods and, to a lesser extent, having inadequate levels of physical activity. A complex and interacting system of factors contributes to increasing rates of overweight and obesity – biological, behavioural, social, psychological, technological, environmental, economic and cultural – operating at all levels from the individual to the family to society as a whole. Examples of these factors include the wide spread availability and affordability of processed foods, most of which have added sugar, high consumption of cheap and tasty sugary drinks, the high prevalence of sedentary “screen time” for children, a lack of access to physical activity opportunities, the marketing of foods and beverages high in fat, sugar and/or sodium to children and increased fast-food availability and increasing portion sizes.  Societal trends have dramatically altered the nature of play and the way children interact with their environment. These trends have included a significant decrease in outdoor recreation, sleep and healthy eating opportunities and now promote an increased dependence on electronic media and sedentary activities.

These changes in our society and the environments we live have encouraged, what is referred to as “obesogenic environments”.  Obesogenic environments are, “the sum of influences that the surroundings, opportunities, or conditions of life have on promoting obesity in individuals or populations.”  Simply put, obesogenic environments are places that encourage people to eat unhealthily and not exercise enough. These are areas where foods high in added sugar, salt and saturated fat are plentiful and the physical environment is not conducive to physical activity opportunities.  Factors in the environment that promote the overconsumption of energy (food) include the easy availability of a wide variety of good-tasting, inexpensive, energy-dense foods in large portions. Other environmental factors tend to reduce total energy expenditure by reducing physical activity. Over time, all of these environmental forces produce gradual weight gain in the population.

Weight gain happens when energy ingested (food and drink) is more than energy burned off (physical activity). A very small number of problems with unhealthy weights in childhood are related to uncommon genetic diseases.

These complex and interacting systems are further complicated by a wide variety of policy decisions made in a number of different sectors that influence childhood obesity.

Children at risk of becoming overweight or obese include children who:

  • consume food and drinks that are high in sugar and saturated fat on a regular basis such as fast food, candy, baked goods, and ESPECIALLY pop and other sugary drinks
  • consume refined grain products on a regular basis
  • have limited intake of vegetables
  • are not physically active each day
  • watch a lot of TV and play a lot of video games, activities that don’t burn calories (sedentary time)
  • live in an environment where healthy eating and physical activity are not encouraged
  • eat to help deal with stress or social problems
  • come from a family of overweight people where genetics may be a factor, especially if healthy eating and physical activity are not a priority in the family
  • come from a low-income family who do not have the resources or time to make healthy eating and active living a priority
  • are exposed to the aggressive marketing of energy-dense foods and beverages to children and families
  • have a lack of information about sound approaches to nutrition
  • have a lack of access, availability and affordability to healthy foods
  • have a genetic disease or hormone disorder such as Prader-Willi syndrome or Cushing’s syndrome

Last updated October, 2019.

References and Additional Resources:

Canadian Task Force on Preventive Health Care (2015). Recommendations for Growth Monitoring, and Prevention and Management of Overweight and Obesity in Children and Youth in Primary Care. http://www.cmaj.ca/content/187/6/411.full

Obesity Reviews (2012). Modern Sedentary Activities Promote Overconsumption of Food in our Current Obesogenic Environment.

Patti Jean Naylor (2015). University of Victoria; School of Exercise Science and Physical Health Education.

Public Health Agency of Canada (2012). Curbing Childhood Obesity: A Federal, Provincial and Territorial Framework for Action to Promote Healthy Weights. http://www.phac-aspc.gc.ca/hp-ps/hl-mvs/framework-cadre/index-eng.php

World Health Organization (2015). Facts and Figures on Childhood Obesity. http://www.who.int/end-childhood-obesity/facts/en/

World Health Organization (2012). Population-Based Approaches to Childhood Obesity Prevention. http://www.who.int/dietphysicalactivity/childhood/approaches/en/

LIVE 5-2-1-0!


or more veggies and fruit per day


no more than two hours of screen time a day

hour of physical activity or more per day


no sugary drinks