20 Nutrition Through the Lifecycle – Puberty – Adolescence


  • Nutrient needs during puberty & adolescence
  • Changes that occur in the body during puberty & adolescence
  • Impact of eating disorders and obesity
The onset of puberty is the beginning of adolescence and is the bridge between the childhood years (9-13) and young adulthood (14-18). Some of the critical physiological changes that occur during this stage include the development of primary sex characteristics, reproductive organs, and the onset of menstruation in females. This life stage is also characterized by secondary sex characteristics, such as the growth of facial and body hair, the development of breasts in girls, and the deepening of boys’ voices. Other physical changes include rapid growth and alterations in body proportions.

The Onset of Puberty (Ages 9 through 13 years)

This period of physical development is divided into two phases. The first phase involves height increases from 20 to 25 percent. Puberty is second to the prenatal period in rapid growth as the long bones stretch to their final adult size. Girls grow 2–8 inches taller, while boys grow 4–12 inches taller. The second phase involves weight gain related to bone, muscle, and fat tissue development. Also, amid puberty, sex hormones trigger the development of reproductive organs and secondary sexual characteristics, such as pubic hair. Girls also develop “curves,” while boys become broader and muscular.

Energy and Macronutrients

The energy requirements for preteens differ according to gender, growth, and activity level. Girls should consume about 1,400 to 2,200 calories per day for ages nine to thirteen, and boys should consume 1,600 to 2,600 calories per day. Physically active preteens who regularly participate in sports or exercise need to eat many calories to increase energy expenditures.

TheAMDR is 45 to 65 percent of daily calories for carbohydrates, a recommended daily allowance of 158–228 grams for 1,400–1,600 daily calories. Carbohydrates that are high in fiber should make up the bulk of intake. The AMDR for protein is 10 to 30 percent of daily calories 35–105 grams for 1,400 daily calories for girls and 40–120 grams for 1boys’,600 daily calories. The AMDR for fat is 25 to 35 percent of daily calories, 39–54 grams for 1,400 daily calories for girls, and 44–62 grams for 1,600 daily calories for boys, depending on caloric intake and activity level.


Essential vitamins needed during puberty include vitamins D, K, and B12. Adequate calcium intake is critical for building bone and preventing osteoporosis later in life. Young females need more iron at the onset of menstruation, while young males need additional iron to develop lean body mass. Almost all of these needs should be met with dietary choices, not supplements; however, iron is an exception, and supplementation my necessary as recommended by the doctor or dietitian.

Iron Requirements

Age Boys Girls


8 mg/day

11 mg/day

8 mg/day

15 mg/day

After puberty, the rate of physical growth slows down. Girls stop growing taller around age sixteen, while boys grow taller until ages eighteen to twenty. One of the psychological and emotional changes that occur during this life stage includes the desire for independence as adolescents develop individual identities apart from their families. As teenagers make more and more of their dietary decisions, parents or other caregivers and authority figures should guide them toward appropriate, nutritious choices. One way that teenagers assert their independence is by choosing what to eat. They have their own money to purchase food and eat more meals away from home. Older adolescents can also be curious and open to new ideas, including trying new food and experimenting with their diet. For example, teens will sometimes skip a main meal and snack instead. That is not necessarily problematic. Their choice of food is more important than the time or place.

However, too many poor choices can make young people nutritionally vulnerable. Teens should be discouraged from eating fast food, high fat and sugar content, or frequent convenience stores and using vending machines, which typically offer poor nutritional selections. Other challenges that teens may face include obesity and eating disorders. At this life stage, young people still need guidance from parents and other caregivers about nutrition-related matters. It can help explain to young people how healthy eating habits can support activities they enjoy, such as athletics, skateboarding, or dancing.

During puberty, growth and development during adolescence differ in males than in females. Both primary and secondary sex characteristics have fully developed, and the growth rate slows with the end of puberty. Fat assumes a more significant percentage of body weight in teenage girls, while teenage boys experience more substantial muscle and bone increases. Also, the motor functions of an older adolescent are comparable to those of an adult.

Energy and Macronutrients

Adolescents have increased appetites due to increased nutritional requirements. Nutrient needs are more significant in adolescence than at any other time in the life cycle, except during pregnancy. The energy requirements for ages fourteen to eighteen are 1,800 to 2,400 calories for girls and 2,000 to 3,200 calories for boys, depending on activity level. The extra energy required for physical development during the teenaged years should be obtained from foods that provide nutrients instead of “empty calories.” Also, teens who participate in sports must meet their increased energy needs.

Older adolescents are more responsible for their dietary choices than younger children, but parents and caregivers must ensure that teens continue to meet their nutrient needs. The AMDR is 45 to 65 percent of daily calories (203–293 grams for 1,800 daily calories) for carbohydrates. Adolescents require more grain servings than younger children and eat whole grains, such as wheat, oats, barley, and brown rice. The Institute of Medicine recommends higher protein intake for growth in adolescents. The AMDR for protein is 10 to 30 percent of daily calories (45–135 grams for 1,800 daily calories), and lean proteins, such as meat, poultry, fish, beans, nuts, and seeds, are excellent ways to meet those nutritional needs.

The AMDR for fat is 25 to 35 percent of daily calories (50–70 grams for 1,800 daily calories), and the AMDR for fiber is 25–34 grams per day, depending on daily calories and activity level. Young athletes and other physically active teens need to intake enough fluids because they are at a higher risk of becoming dehydrated.


Micronutrient recommendations for adolescents are mostly the same as for adults. However, children this age need more minerals to promote bone growth (e.g., calcium and phosphorus, iron and zinc for girls). Again, vitamins and minerals should be obtained from food first, supplementing certain micronutrients only (iron).

The most important micronutrients for adolescents are calcium, vitamin D, vitamin A, and iron. Adequate calcium and vitamin D are essential for building bone mass. The recommendation for calcium is 1,300 milligrams for both boys and girls. Low-fat milk and cheeses are excellent sources of calcium and help young people avoid saturated fat and cholesterol. It can also help adolescents consume products fortified with calcium, such as breakfast cereals and orange juice. Iron supports the growth of muscle and lean body mass. Adolescent girls also need to ensure sufficient iron intake before menstruating. Girls ages twelve to eighteen require 15 milligrams of iron per day. Increased amounts of vitamin C from orange juice and other sources can aid in iron absorption. Also, adequate fruit and vegetable intake allow for meeting vitamin A needs.

Eating Disorders

Many teens struggle with an eating disorder, which can have a detrimental effect on diet and health. These disorders are more prevalent among adolescent girls but have increased among adolescent boys in recent years. Because eating disorders often lead to malnourishment, adolescents with an eating disorder are deprived of the crucial nutrients their still-growing bodies need. Eating disorders stem from stress, low self-esteem, and other psychological and emotional issues. Parents need to watch for signs and symptoms of these disorders, including sudden weight loss, lethargy, vomiting after meals, and the use of appetite suppressants. Eating disorders can lead to severe complications or be fatal if left untreated. Treatment includes cognitive, behavioral, and nutritional therapy.

Childhood and Adolescent Obesity

Children need adequate caloric intake for growth, and it is important not to impose very restrictive diets. However, exceeding caloric requirements regularly can lead to childhood obesity, which has become a significant problem in North America. Nearly one in three US children and adolescents are overweight or obese.

There are several reasons for this problem, including:

  • larger portion sizes
  • limited access to nutrient-rich foods
  • increased access to fast foods and vending machines
  • lack of breastfeeding support
  • declining physical education programs in schools
  • insufficient physical activity and a sedentary lifestyle
  • media messages encouraging the consumption of unhealthy foods

Children who suffer from obesity are more likely to become overweight or obese adults. Obesity has a profound effect on self-esteem, energy, and activity level. It is a significant risk factor for many diseases later in life, including cardiovascular disease, Type 2 diabetes, stroke, hypertension, and certain cancers.

A percentile for body mass index (BMI) specific to age and sex determines if a child is overweight or obese. This is more appropriate than the BMI categories used for adults because children’s body composition varies as they develop and differs between boys and girls. If a child gains weight inappropriate to grow, parents and caregivers should limit energy-dense, nutrient-poor snack foods. It is also highly beneficial to increase a child’s physical activity and limit sedentary activities, such as watching television, playing video games, or surfing the Internet.

Programs to address childhood obesity can include behavior modification, exercise counseling, psychological support or therapy, family counseling, and family meal-planning advice. For most, the goal is not weight loss but instead allowing height to catch up with weight as the child grows. Rapid weight loss is not recommended for preteens or younger children due to the risk of deficiencies and stunted growth.

Avoiding Added Sugars

One major contributing factor to childhood obesity is the consumption of added sugars. Added sugars include sugar added to food at the table and ingredients in bread, cookies, cakes, pies, jams, and soft drinks. The added sugar in store-bought items may be white, brown sugar, high-fructose corn syrup, honey, malt syrup, maple syrup, molasses, anhydrous dextrose, crystal dextrose, and concentrated fruit juice. (Not included are sugars that occur naturally in foods, such as the lactose in milk or the fructose in fruits.) Besides, sugars are often “hidden” in items added to foods after preparation, such as ketchup, salad dressing, and other condiments. The primary offenders are processed and packaged foods, soda, and other beverages. These foods are not only high in sugar; they are also light in terms of nutrients and often take the place of healthier options.

Knowledge Check



Learning Objectives

  • Recognize nutrient needs during puberty & adolescence. (MCCCD Competency 4)
  • Discuss changes that occur in the body during puberty & adolescence. (MCCCD Competency 4)
  • Describe the health challenges with obesity during this life stage. (MCCCD Competency 9)
  • Explain why iron needs increase during this life stage. (MCCCD Competency 9)



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Nutrition Essentials Copyright © 2020 by Stephanie Green and Kelli Shallal is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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