9.2 Nutrition

All the changes of puberty depend on adequate nourishment, yet many adolescents do not consume enough vitamins or minerals. Teenagers often skip breakfast, eat at midnight, guzzle down soft drinks, and munch on salty, processed snacks. One reason is that their hormones affect their diurnal rhythms, including their appetites; another reason is that they seek independence by eating what they want, when they want.

In 2004, the Canadian government created its first national survey of Canadians’ eating habits since the 1970s. The Canadian Community Health Survey (CCHS) queried more than 35 000 people and asked them to recall what and when they had eaten in the last 24 hours. The findings were not promising, especially among adolescents. About 62 percent of girls and 68 percent of boys between the ages of 9 and 13 did not meet Canada’s Food Guide’s recommendation for at least five daily servings of fruit and vegetables. The Food Guide also recommends a daily serving of 100 to 300 grams of cooked meat or alternatives such as beans or eggs. According to the survey, 14 to 18 percent of girls aged 9 to 18 ate less than 100 grams of meat or other protein sources per day (Garriguet, 2004).

Diet Deficiencies

Diet Worldwide, adolescent obesity is increasing. However, these girls are addressing their weight challenges by eating balanced meals, restricting fat consumption, and walking more than 10 000 steps a day. For people who are used to eating poorly, this way of eating takes some getting used to.

STEPHAN GLADIEU/GETTY IMAGES

Deficiencies of iron, calcium, zinc, and other minerals are especially common after puberty. Anemia, which is a deficiency of iron, is more likely among adolescent girls than among people of any other age or gender. This is partly because adolescents of both sexes in every nation do not eat enough iron-rich foods either because they are not able to afford them or because they choose to eat iron-poor chips, sweets, and fries instead. Coffee, tea, and soft drinks also reduce iron absorption. In addition, for girls, menstruation depletes iron. Boys, who naturally require more iron to be healthy, may also be iron-deficient if they push their bodies in physical labour or sports: Muscles need iron for growth and strength.

Similarly, although the daily recommended intake of calcium for teenagers is 1300 milligrams, the average North American teen consumes less than 500 milligrams a day. Although Canada’s Food Guide recommends that 10- to 16-year-olds have three to four servings of high-calcium products such as milk, cheese, or yogourt per day, the 2004 CCHS found that 61 percent of boys and 83 percent of girls in this age bracket did not meet the minimum recommended servings.

While teens’ consumption of milk products is down, the CCHS also found that their intake of soft drinks and other sugary drinks is higher than it should be:

Such data led one researcher, Susan Whiting of the University of Saskatchewan, to tell the CBC, “You don’t want people to be too complacent about these drinks. I think other research shows that if it gets out of hand, these sugary beverages can make a big impact on weight” (CBC News, 2012). Too many soft drinks and too little calcium between the ages of 10 and 20, when about half of adult bone mass is acquired, also means that many contemporary teenagers will develop osteoporosis (fragile bones), a major cause of disability in late adulthood.

Body Image

One reason for poor nutrition among teenagers is anxiety about body image—that is, a person’s idea of how his or her body looks. Few teenagers welcome every physical change in their bodies. Instead, they exaggerate imperfections (as did the girl in the story that opens this chapter) and sacrifice future health to improve current body image.

Girls diet because they want to be thinner (Halpern et al., 2005). Boys want to look taller and stronger, a concern that increases from ages 12 to 17 (D. Jones & Crawford, 2005). In both sexes and in adolescents of all ethnicities, dissatisfaction with body image is linked to low self-esteem (van den Berg et al., 2010).

Thus, as the hormones of puberty awaken sexual interest, both sexes become less happy with their own bodies and more superficial in their evaluation of the other sex. This is true worldwide. A longitudinal study in Korea found that, as in the West, body image dissatisfaction began in early adolescence and increased until age 15 or so (Kim & Kim, 2009).

Eating Disorders

One result of dissatisfaction with body image is that many teenagers, mostly girls, eat erratically or ingest drugs (especially diet pills) to lose weight; others, mostly boys, take steroids to increase muscle mass. Eating disorders are rare in childhood but increase dramatically at puberty, accompanied by distorted body image, food obsession, and depression (Bulik et al., 2008; Hrabosky & Thomas, 2008).

Adolescents sometimes switch from obsessive dieting to overeating and back again. Obesity, which is a problem at every age, is discussed primarily in other chapters. Here we describe two other eating disorders that are common in adolescence and early adulthood.

Effects of Anorexia Elize, seen here at age 20, has been suffering from anorexia since she was 18 after she went on a diet to lose weight. She eats no more than 1200 calories per day. Some clinicians suggest that starving oneself is a destructive way to avoid the womanly body that develops at puberty.

FRED DUFOUR/AFP/GETTY IMAGES

AnorexiaSome young women (and occasionally men) suffer from anorexia nervosa, a disorder characterized by severe calorie restriction, or a cycle of bingeing followed by purging, that can lead to death by organ failure or suicide for between 5 and 20 percent of sufferers. If a person’s body mass index (BMI) is 17 or lower, and if she or he has a fixation with weight—believing that she or he is overweight despite all evidence to the contrary—anorexia is suspected. Anorexia was undiagnosed until about 1950, when some high-achieving, upper-class young women became so emaciated that they died. Soon anorexia became evident among younger women (the rate spikes at puberty and again in emerging adulthood), among men (especially wrestlers, runners, and dancers), and in every nation and ethnic group (Chao et al., 2008).

According to DSM-5, anorexia is officially diagnosed when three symptoms are present:

1. significantly low body weight for developmental stage (BMI of 17 or lower)
2. intense fear of weight gain
3. disturbed body perception and denial of the problem.

Certain alleles increase the risk of anorexia (J. K. Young, 2010), but context is crucial. The disorder seems related to cultural pressure to be thin.

BulimiaAbout three times as common as anorexia is bulimia nervosa, sometimes called the binge–purge syndrome. People with bulimia overeat compulsively, wolfing down thousands of calories within an hour or two, and then purge by vomiting or using laxatives or diuretics. They may also engage in excessive exercise.

Most bulimics are close to normal in weight and are unlikely to starve. However, they risk serious health problems, including damage to their gastrointestinal systems and cardiac arrest from electrolyte imbalance (Shannon, 2007). They also risk compulsion and depression, including thoughts of suicide (Parylak et al., 2011).

According to DSM-5, 1 to 3 percent of female teenagers and young adults are clinically bulimic. They have the following three symptoms:

1. bingeing and purging at least once a week for three months
2. uncontrollable urges to overeat
3. sense of self inordinately tied to body shape and weight.

In addition to anorexia nervosa and bulimia, DSM-5 now includes a new diagnostic category, binge-eating disorder, which allows some individuals, whose condition was previously considered non-specific or undefined, to develop a clearer understanding of their symptoms and behaviours.

People with an eating disorder tend to be perfectionists at school or at work and to have low self-esteem and an inaccurate body image. Although the precise causes of developing an eating disorder are unclear, several factors have been linked to these disorders.

The way society views attractiveness and the implicit message that thinness is desirable may be one factor. Also, young people who have an immediate family member with an eating disorder sometimes develop a similar disorder, which implies a genetic link (Bulik et al., 2005). Lastly, people with other emotional or psychological disorders, especially substance abuse, personality disorders, or affective disorders such as depression are much more likely to develop an eating disorder (K. A. Langlois et al., 2012).