Textbook Notes (280,000)
CA (170,000)
U of G (10,000)
NUTR (100)
Chapter 14

NUTR 2050 Chapter Notes - Chapter 14: Secondary Sex Characteristic, Pubic Hair, Thelarche


Department
Nutrition
Course Code
NUTR 2050
Professor
Simone Holligan
Chapter
14

This preview shows pages 1-2. to view the full 8 pages of the document.
Chapter 14: Adolescent Nutrition
Introduction
Adolescence is defined as the period of life between 11 and 21 years of age. It is a time of profound biological,
emotional, social, and cognitive changes during which a child develops into an adult. Physical, emotional, and
cognitive maturity is accomplished during adolescence. The tasks of adolescence, not unlike those
experienced during the toddler years, include the development of a personal identity and a unique value
system separate from parents and other family members, a struggle for personal independence accompanied
by the need for economic and emotional family support, and adjustment to a new body that has changed in
shape, size, and physiological capacity.
Nutritional Needs in a Time of Change
The dramatic physical growth and development experienced by adolescents significantly increases their needs
for energy, protein, vitamins, and minerals. However, the struggle for independence that characterizes
adolescent physiological development often leads to the development of health-compromising eating
behaviours, such as excessive dieting, meal skipping, use of unconventional nutritional and non-nutritional
supplements, and the adoption of fad diets. The challenging behaviours of adolescents can become
opportunities for change at a time during which adult health behaviours are being formed.
Normal Physical Growth and Development
Early adolescence encompasses the occurrence of puberty, the physical transformation of a child into a young
adult. The biological changes that occur during puberty include sexual maturation, increases in height and
weight, accumulation of skeletal mass, and changes in body composition. Even though the sequence of these
events during puberty is consistent among adolescents, the age of onset, duration, and tempo of these events
vary a great deal between and within individuals. For this reason, sexual maturation (or biological age) should
be used to assess biological growth and development and the individual nutritional needs of adolescents rather
than chronological age. Sexual Maturation Rating (SMR), also known as “Tanner Stages”, is a scale of
secondary sexual characteristics that allows health professionals to assess the degree of pubertal
maturation among adolescents, regardless of chronological age. SMR is based on breast development and the
appearance of pubic hair among females, and on testicular and penile development and the appearance of
pubic hair among males. SMR stage 1 corresponds with prepubertal growth and development, while stages 2
through 5 denote the occurrence of puberty. At SMR stage 5, sexual maturation has concluded.
The onset of menses (process of menstruation) and changes in height relative to the development of
secondary sexual characteristics that occur in female during puberty are shown in illustration 14.2 p 363.
Among females, the first signs of puberty are the development of breast buds and sparse, fine pubic hair
occurring on average between 8-13 years of age. Menarche occurs 2-4 years after the initial development of
breast buds and pubic hair, most commonly during SMR stage 4. The average age of menarche is 12.4 years,
but menarche can occur as early as 9 or 10 years or as late as 17 years of age. Onset of the linear growth
spurt occurs most commonly during SMR stage 2 in females, beginning between the ages of 9.5 and 14.5
years in most females. Peak velocity in linear growth occurs during the end of SMR stage 2 and during stage
3, approx 6-12 months prior to menarche.
During the peak of the adolescent growth spurt, females gain approx 3.5 inches a year. The linear growth spurt
lasts 24-26 months, casing by age 1 in most females. Some adolescent females experience small increments
of growth past age 19 years. Enlargement of the testes and change in scrotal coloring are most often first
signs of puberty among males, occurring between 10.5 and 14.5 years, with 11.6 the avg age. The
development of pubic hair is also common during SMR stage 2. Testicular enlargement begins between the
ages of 9.5 and 13.5 years in males, and concludes between the ages of 12.7 and 17 years. The average age

Only pages 1-2 are available for preview. Some parts have been intentionally blurred.

of “spermarche” is approximately 14 among males. The peak velocity of linear growth occurs at 14.4 years of
age, on average. At the peak of growth spurt, adolescent males will increase their height by 2.8 to 4.8 inches a
year. Linear growth will continue throughout adolescence, at a progressively slower rate, ceasing at about 21
years of age.
Changes in Weight, Body Composition, and Skeletal Mass
As much as 50% of ideal adult body weight is gained during adolescence. Among females, peak weight gain
follows the linear growth spurt by 3-6 months. During the peak velocity of weight change, which occurs at an
average age of 12.5 years, girls will gain approximately 18.3 lb per year. Weight gain slows around the time of
menarche, but will continue into late adolescence. Adolescent females may gain as much as 14lb during the
latter half of adolescence. Peak accumulation of muscle mass occurs arond or just after the onset of menses.
Body composition changes dramatically among females during puberty with average lean body mass falling
from 80-74% of body weight while average body fat increases from 1-2% at full maturity. Females experience a
44% increase in lean body mass and a 120% increase in body fat during puberty. Body fat levels peak among
teenaged females between the ages of 15-16. Research suggests that a level of 17% body fat is required for
menarche to occur and that 25% body fat is required for the development and maintenance of regular
ovulatory cycles.
Even though the accumulation of body fat by females is obviously a normal and physiologically necessary
process, adolescent females often view it negatively. Among males, peak weight gain coincides with the timing
of peak linear growth and peak muscle mass accumulation. During peak weight gain, adolescent males gain
an average of 20 pounds per year. Body fat decreases in males during adolescence, resulting in an average of
approx 12% by the end of puberty. Almost half of adult peak bone mass is accrued during adolescence. By age
18, more than 90% of adult skeletal mass has been formed. Because bone is composed largely of calcium,
phosphorus, and protein and because a great deal of bone mass is accrued during adolescence, adequate
intakes of these nutrients are critical to support optimal bone growth and development.
Normal Psychosocial Development
Psychosocial development is most readily understood when it is divided into 3 periods: early adolescence (11-
14), middle (15-17) and late (18-21). Individuals begin to experience dramatic biological changes related to
puberty during early adolescence. The development of body image and an increased awareness of sexuality
are central psychosocial tasks during this period of adolescence. Peer influence is very strong during early
adolescence. Young teens, conscious of their physical appearance and social behaviours, strive to “fit in” with
their peer group. Consequently, teens express their ability and willingness to fit in with a group of peers by
adopting food preferences and making food choices based on peer influences and by refuting family
preferences and choices. In other cases, the choices are based on peer pressure may lead to poor dietary
intake. The wide chronological age range during which pubertal growth and development begins and proceeds
can become a major source of personal dissatisfaction for many adolescents.
Cognitively, early adolescence is a time dominated by concrete thinking, egocentrism, and impulsive
behaviour. Abstract reasoning abilities are not yet developed to a great extent in most adolescents. Middle
adolescence marks the development of emotional and social independence from family, especially parents.
Conflicts over personal issues, including eating and physical activity behaviours, are heightened during middle
adolescence. Peer groups become more influential and their influence on food choices peaks. Physical growth
and development are mostly completed during this stage. Adolescents may believe they are invincible during
this stage of development.
The emergence of abstract reasoning skills occurs rapidly during middle adolescence; however, these skills
may not be applied to all areas of life. Adolescents will revert to concrete thinking skills if they feel
You're Reading a Preview

Unlock to view full version

Only pages 1-2 are available for preview. Some parts have been intentionally blurred.

overwhelmed or experience psychosocial stress. Late adolescence is characterized by the development of a
personal identify and individual moral beliefs. Physical growth and development is largely concluded, and body
image issues are less prevalent. Adolescents become increasingly less economically and emotionally
dependent on parents. Relationships with one individual become more influential than the need to fit in with a
group of peers. Personal choice emerges. Abstract thinking capabilities are realized during late adolescence,
which assists teens in developing a sense of future goals and interests.
Health and Nutrition Related Behaviours During Adolescence
Eating patterns and behaviours of adolescents are influenced by many factors, including peer influences,
parental modeling, food availability, food preferences, cost, convenience, personal and cultural beliefs, mass
media, and body image (illustration 14.4 p 366). Personal factors that influence eating behaviour include
attitudes, beliefs, food preferences, self-efficacy, and biological changes. Environmental factors include the
immediate social environment such as family, friends, and peer networks, and other factors such as school,
fast-food outlets, and social and cultural norms. Macrosystem factors, which include food availability, food
production and distribution systems, and mass media and advertising, play a more distal and indirect roles in
determining food patterns, yet can exert a powerful influence on specific food choices. To improve the eating
patterns of youth, nutrition interventions should be aimed at each of the three levels of influence. In addition to
these influencing factors, socioeconomic status and racial/ethnic background also play a role in shaping
adolescent eating patterns. Eating habits of adolescents are not static; they fluctuate throughout adolescence
in relation to psychosocial and cognitive development. These changes often result from increasingly hectic
schedule and greater perceived barriers to healthy eating as adolescents mature and take on additional
responsibilities such as participation in extra curricular activities at school and employment outside of the
home. Adolescents lead busy lives.
Snacking, skipping meals, and eating foods that are cheap and quick, such as vending machine snacks and
fast foods, are commonplace behaviours among adolescents who report a lack of time as a major barrier to
healthy eating. 83% of adolescents report snacking with a mean 1.7 snacks on any given day. Almost ¼ report
eating 3+ snacks per day. Snacks account for 23% to 39% of daily food energy among adolescents, with 27-
35% of discretionary calories, 24% of total fats, and 31-43% added sugars provided by snacks alone. Although
increased frequency of snacking among teens is associated with greater energy intakes, a greater frequency of
snacking among adolescents does not seem to be associated with higher BMI values. Unfortunately, the food
choices made by adolescents while snacking tend to favor foods high in sugar, sodium, and fat. Soft drinks are
among the most commonly chosen snacks for adolescents; they are the number one source of energy added
sugars in the diets of teens, accounting for 9% of total energy intake and 45% of added sugar intakes. Other
snack foods are significant sources of energy, fat and sugars in the diets of teenagers include fruit drinks, dairy
desserts, salty snacks, and pizza.
The occurrence of meal skipping increases as adolescents mature. Breakfast is the most commonly skipped
meal with up to 27% on any given day. Skipping breakfast can dramatically decrease intakes of energy,
protein, fiber, calcium, and folate due to the absence of breakfast cereal or other nutrient-dense foods
commonly consumed at breakfast. Lunch is skipped by almost 25% and dinner is skipped by up to 8% of
teens. As adolescents mature, they spend less time with family and more with peers. Eating away from home
becomes prevalent and estimated that they consume fast food 2.5 days per week. Fast food consumption is
influenced by proximity of fast food venues to schools and other community setting where teens live and learn.
Research has suggested that fast food restaurants are three to four times more concentrated around schools
than in the general community and that having a fast food venue within a half mile, or 5 minute walk is related
to higher consumption of soda and lower intake of fruits and veggies. Fast food accounts for 17 of the total
energy intake among U.S. adolescents. Fast-food restaurants and food courts are favourite eating places of
teens because they offer an informal setting with inexpensive food choices. These venues also have a high
percentage of teen employees, thus increasing their social value. It is important to note that approximately half
You're Reading a Preview

Unlock to view full version