by Ian Janssen
Healthy living during youth includes being physically active and eating a healthy diet. But what is physical activity and how much of it is enough? What are sedentary activities and how often are students engaged in them? What are the eating habits and weight-loss practices of youths? Besides measuring the physical activities and food consumption or eating that are connected to healthy living, this chapter looks at indicators of unhealthy living among Canada's young people, including overweight, obesity, and body image dissatisfaction.
In general, physical activities of moderate to vigorous intensity are those that will make the individual breathe more deeply and rapidly and increase his or her body temperature (e.g., make them feel warm, sweat).
In its simplest sense, physical activity is defined as any bodily movement produced by the muscles that results in an increase in energy expenditure. Physical activity therefore includes non-vigorous tasks, such as light walking, and vigorous tasks, such as brisk walking, jogging/ running, bicycling, playing soccer, and playing basketball. In young people, physical activity needs to be of at least a moderate intensity to generate health benefits.
Although physical activity results in many health benefits, these benefits do not motivate young people to be physically active. Rather, they tend to participate in physical activity for fun and enjoyment, and for social reasons.
Parents, health-care practitioners, and policymakers are concerned about low levels of physical activity among young people. The health benefits of regular physical activity in young people are numerous and impact on several areas of physical and mental health.
Physical health benefits include the regulation of body weight and chronic-disease risk factors (e.g., blood pressure, blood cholesterol), improved fitness, and the development of healthy and strong bones. Mental health benefits include improved self-efficacy, emotional health, and self-image, and absence of depression symptoms.
Canada has a Physical Activity Guide for children and another for youth. As an immediate goal, the Guides recommend that inactive young people increase the amount of time they currently spend being physically active by at least 30 minutes per day and decrease the time they spend watching television, playing computer games, and surfing the internet by at least 30 minutes per day. As a longer-term goal, young people should strive, over several months, to accumulate a total of at least 90 minutes more physical activity per day and reduce by a total of at least 90 minutes per day the amount of time spent in sedentary activities. Refer to Canada's Physical Activity Guide to Healthy Active Living at the following web address for more information on appropriate physical activity choices, prescription, and health benefits: Public Health Agency of Canada - Physical Activity.
Sedentary behaviours are different from physical activity and consist of activities in which there is little movement or energy expenditure. These activities include watching television, playing video games, using the computer, doing homework, and reading.
It is impossible for anyone to be physically active during all waking hours. The goal is not to eliminate sedentary behaviours, but to keep young people's sedentary activities to a reasonable level. In particular, screen-time activities, such as watching television, using the computer, and playing video games, can compete with time for participation in physical activity.
An additional cause for concern is that some sedentary pursuits, most notably television and video games, have been linked to violent and aggressive behaviours, substance use and abuse, body image issues, unhealthy eating, and obesity. Most of these negative health impacts are the consequence of the inappropriate advertising (e.g., commercials for foods low in nutritional value and high in calories) and messaging (e.g., excessive sexual content and violence) that are part of the media environment.Footnote 1
Food frequency refers to the number of times one eats a given food item. Food frequency questionnaires are often used in surveys with large sample sizes, such as the HBSC. They provide information on the number of times (but not the exact amount) that specific food items were consumed. Healthy and nutritious food items need to be eaten on a regular basis. Young people should eat certain foods, such as fruits and vegetables and items from the other major food groups, several times a day to maintain good health and optimal growth and development. Similarly, unhealthy food items (e.g., junk food) that are filled with empty calories and lacking in nutritional value should be eaten very infrequently. Overconsumption of unhealthy foods can lead to obesity and nutritional deficiencies.
Simply defined, overweight and obesity represent conditions in which an individual has excess body fat, to the extent that it influences his or her health in a negative way. These conditions result from a long-term imbalance between the amount of energy (or calories) consumed in the diet and the amount of energy used by the body. Over time, excessive eating and/or limited levels of moderate-to-vigorous physical activity can lead to overweight and obesity.
Over the past few years, obesity among young people has become a leading public health issue in Canada. Overweight and obesity are associated with numerous health consequences in Canadian students. These include elevated risk factors associated with heart disease and type 2 diabetes (e.g., increased blood cholesterol, blood pressure, and blood sugar levels), problems with the bones and joints, poor emotional health and well-being, and a reduced overall quality of life.Footnote 2 Furthermore, overweight and obesity that manifest in childhood and adolescence tend to carry on into adulthood, suggesting that most young people with these conditions will struggle with weight-related issues for the rest of their lives.
Dangerous and unrealistic cultural ideals of slimness have filtered down to the child and adolescent population. Young people, particularly girls, often feel dissatisfied with their body weight and size. Sometimes weight-loss practices are justified, e.g., in an obese youth; other times they are not, e.g., in a youth who has a normal weight or in a youth who is already underweight.
Having a poor body image is highly related to low self-esteem and, in some situations, can lead to eating disorders, such as bulimia and anorexia. Although properly monitored and regulated weight-control practices may be appropriate for obese youngsters, other weight-loss practices may negatively affect a young person's psychological well-being and, in more extreme situations, result in nutritional deficiencies that delay or damage his or her development.
Young people who report 60 minutes of physical activity or more on at least five days of the week are considered to be physically active, while those participating in lesser amounts are considered to be physically inactive.Footnote 3
We asked students to indicate how many days in the past seven days and in a typical or usual week they were physically active at a moderate to vigorous intensity for at least 60 minutes. Students also reported the number of hours in a usual week in which they exercised or were physically active in class time at school, in free time at school, and in free time outside of school hours. Information about frequency of exercise in free time outside of school hours was also gathered.
A series of questions was used to determine how many hours per usual day young people engaged in the following sedentary activities: watching television (including videocassettes and DVDs), playing video games on a computer or console (Playstation, Xbox, GameCube, etc.), and using a computer in free time (including doing homework, chatting online, internet browsing, emailing, etc.). Two hours or more per day for each of these screen-time activities is considered excessive.Footnote 4
BMI is calculated as an individual's body weight divided by the square of the individual's height. The standard international unit is kg/m2.
Students were asked to report how frequently they ate various food items. For each food item, response options ranged from never to more than once per day. Young people reported their height and weight and these values were used to calculate the body mass index or BMI. International ageand gender-specific BMI standards for children and youth were used to classify the participants as being of normal weight, overweight, or obese.Footnote 5
We asked students if they felt their body was much too thin, a bit too thin, about the right size, a bit too fat, or much too fat. Responses of "much too" and "a bit too" were combined for both thin and fat. We also asked if they were currently dieting or doing something else (e.g., exercising) in an attempt to lose weight.
In this chapter, we report on the physical activity levels, sedentary habits, food frequency patterns, overweight and obesity levels, and body image and weight-loss practices of Canada's young people.
Physical activity, food frequency, and obesity are then each examined in relation to some of the contextual variables: physical activity in relation to parent trust and communication, academic achievement, attitude towards school, and family affluence; food frequency in relation to family affluence; and obesity in relation to academic achievement and family affluence.