Adolescence

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Early adolescence

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11-14 years

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Middle adolescence

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15-17 years

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Late adolescence

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18-21 years (crosses over with early adulthood)

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Nutritional Needs

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• Substantial physical, emotional and cognitive maturation
• Rapid physical growth affects nutrient needs
• strong desire for independence: can influence food choices

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Physical Development

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Puberty begins during the Early Adolescence - biological changes of puberty include:

• increase in height and weight
• sexual maturation
• changes in body composition
• accumulation of skeletal mass
• order of changes is consistent, but the timing is not!

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Physical Development

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• Variations in reaching sexual maturity affect nutrition requirements of adolescents
• sexual maturation (also called biological age)- not chronological age- should be used to assess nutritional needs

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Sexual Maturation Rating

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Sexual Maturation Rating (SMR, also called "Tanner Stages"): Scale to assess degree of sexual maturation - Rated on a 5 point scale (SMR 1-5):

• SMR Stage 1 = pre-puburtal growth and development
• SMR Stages 2-5 = occurrences of puberty
• SMR Stage 5 = sexual maturation has concluded

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Sexual Maturation Rating

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• Boys: genital development and pubic hair growth
• Girls: breast development and pubic hair growth
• Evaluation of SMR can be completed by a physician or adolescents can rate themselves

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Sexual Maturation in Females

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• Menarche: onset of first menstrual period
• Occurs 2-4 years after initial development of breasts (SMR 4)
• Age of menarche ranges from 10-17 years (avg 12.4 yrs)
• Peak velocity of linear growth occurs ~6 to 12 months prior to menarche (SMR 3)
• In highly competitive athletes, severly restrictive diets may delay or slow growth

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Body Composition Changes in Females

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• Peak weight gain follows linear growth spurt by 3 to 6 months
• Increase in body fat
• Decrease in lean body mass from 80% to 74% of body weight

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What percentage of body fat increase happens during puberty for females?

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120%

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Body Fat Levels in Females

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• Low: <20%; Moderate: 28%; high/obese: >35%
• 17% body fat is required for menarche to occur
• 25% body fat needed to maintain normal menstruation cycles (ovulation)

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Sexual Maturation in Males

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• Large variation in chronological age at which sexual maturation takes place
• Peak velocity of linear growth occurs during SMR 4 and ends with the appearance of facial hair
• Linear growth continues throughout adolescence at a slower rate until ~ 21 years

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Body Composition Changes in Males

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• Peak weight gain at the same time as peak linear growth
• Peak weight gain, ~20 lbs/year
• Body fat decreases to ~12%

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Skeletal Mass

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• ~Half of bone mass is accrued in adolescence
• By 18: 90% of skeletal mass is formed

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Energy needs are influenced by:

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• activity level
• basal metabolic rate (BMR)
• pubertal growth and development

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Level of physical activity...

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declines during adolescence resulting in reduced energy requirements

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Energy Ranges:

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• Males: 2200-3100 kcal/day
• Females: 2000-2400 kcal/day

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Calculating Estimated Energy Requirements

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Boys 9-18 years:

EER = 88.5 - (61.9 x age) + PA x{26.7 x weight[kg] + (903 x height[m])} + 25

Girls 9-18 years:

EER = 135.3 - (30.8 x age) + PA x{10.0 x weight[kg] + (934 x height[m])} + 25

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Calculating Estimated Energy Requirements

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• Age in years, weight in kilograms, height in meters
• Physical activity (PA) according to chart

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Acceptable Macronutrient Distribution Range (AMDR)

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The range of intake for a particular energy source (protein, fat or carb), expressed as a percentage of total energy (kcal), that is associated with reduced risk of chronic disease while providing adequate intakes of essential nutrients

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Protein Requirements

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• Influenced by amount needed to maintain existing and lean body mass and develops new muscle
• DRI: 0.85 g/kg body weight (AMDR: 10-30%)

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Low protein intakes during adolescence linked to:

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• reductions in linear growth
• delays in sexual maturation
• reduced lean body masses

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Carbohydrate and Fibre

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Carbohydrates: 130 g/day or 45-65%

Dietary Fibre:

• Males: 9-13 years - 31 g/day
• Males: 14-18 years - 38 g/day
  
• Females: 9-13 years - 26 g/day
• Females: 14-18 years - 26 g/day
  

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Dietary Fat

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• Required as dietary fat and essential fatty acids for growth and development
• 25-35% E from total fat
• 0.6-1.2% E from omega 3 fatty acids (LA, ALA)
• <10% E from saturated fats

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Calcium

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• AI is critical to ensure peak bone mass
• Absorption highest for females around menarche, for males during early adolescence
• ~4 times more calcium absorbed during early adolescence compared to adulthood
• Adolescents who do not include dairy should consume calcium-fortified foods
• Soft drink consumption displaces nutrient-dense beverages such as milk and fortified juices
• RDA for 9-18 years is 1300 mg/day

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Vitamin D

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• Facilitates intestinal absorption of calcium (and phosphorus)
• Essential for bone formation
• synthesized by the body via skin exposure to (UV B rays of) sunlight
• In northern latitudes, may require supplementation
• DRI: 600 IU per day
• Indigenous people are at risk for low exposure, diet not always inclusive, many are lactose intolerant

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Iron

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• Rapid rate of linear growth and increase in blood volume
• For females, needs highest after menarche (15 mg/day)
• For males, after growth spurt (11 mg/day)
• Deficiencies in 9% of 12-15 year old females and 5% of 12-16 year old males

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Zinc

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Needed for sexual maturation and growth, especially in males

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B Vitamins

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• Folate, Vit B12, niacin, riboflavin, thiamin
  
• requirements are double those of elementary school age

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Selected Nutrient Intakes from Canadian Community Health Survey (CCHS)

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• Caloric intakes are high for both sexes
• Neither sexes have good intake of fibre
• Fat intakes are high
• Low Vit D and Calcium intakes for females
• Sodium intake is very high, especially for males (at risk for hypertension, high blood pressure, etc.)

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The Teen Brain

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• ability to reason, rational thought may be limited
• live in the moment; limited consideration of long-term consequences
• reward benefits are more important than possible risk

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The Teen Brain - video

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• considered a late childhood brain
• still at peak learning; can imprint/memorize
• connectivity of brain develops from back to front
• last place is frontal lobe via mylenation (key for insight and judgment)
• Teens are very sharp by not great at judging

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Social and Emotional Development in Early Adolescence

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• Strong need for social acceptance from peers
• Body image may change as a result of changes in body shape
• Increased awareness of sexuality
• Strong sense of impulsivity

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Social and Emotional Development in Middle and Late Adolescence

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• Increased opportunities for employment and outside activities
• Greater autonomy from parents
• Continued need for social acceptance from peers
• Increased awareness of social and moral issues

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Vegetarian Diets During Adolescence

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About 4% of adolescents report being vegetarian

Reasons being:

• cultural or religious beliefs
• moral or ethical concerns
• health beliefs
• to restrict fat and/or calories
• a means of independence from family

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Vegetarian Eating Habits

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• 2516 US adolescents, age 15-23

Compared to non-vegetarians, vegetarians had:

• better Fruit and Veg intake, less overweight/obesity
• more eating disorders, more weight controlling behaviour

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Dietary Guidance

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• No specific guidance from Health Canada
• Lacto-ovo vegetarians can meet needs following EWCFG by:
• Choosing legumes, nuts, tofu as alternatives to meat; fortified soy beverage as milk alternative
• For Vegans, EWCFG will not be adequate
• Need for animal-derived foods to supplement: Calcium, zinc and Vitamins D, B6 and B12

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Position of Dietitians of Canada on Vegetarian Diets (2003)

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• Depends on level of restriction; too much restriction, there is a concern with adequacy especially for growing children and adolescence
• can be associated with eating disorders
• fortification and supplements will help vegans to achieve adequate nutrition

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BUT...The teen brain

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Ability to plan and problem solve may be limited

• Teens can be supported and educated by parents and caregivers
  
• If teens are motivated by weight loss, caregivers need to try to understand these motivations

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Physical Activity Guide for Children 5-17

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• 60+ min/day of moderate to intense exercise
• 3+ days/week, intense exercise
• 3+ days/week, muscle building exercise

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Health Behaviour in School-aged Children Study

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• Trend shows that physical activity decreased as grades increased (Grade 6-10)
• Females were less active than males in general
  

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Physical Activity CCHS

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• 80% of adolescents not doing ANY daily physical activity
• 14% use the computer more than 10 hours a day

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Association between body satisfaction and weight-related behaviours

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FEMALES:

• Increase in extreme weight control behaviours
• Increase in binge eating
• Decrease in physical activity
• Decrease in Fruit and veg intake

MALES:

• Increase in extreme weight control behaviours
• Increase in binge eating
  
• Decrease in physical activity
  

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Eating Disorders

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Three clinically defined/diagnosed:

• anorexia nervosa
• bulimia nervosa
• binge eating disorder

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Continuum of eating concerns and disorders

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Body dissatisfaction -> dieting behaviours -> disordered eating -> clinically significant eating disorders

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Some Canadian Statistics

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• (2000) 46% of girls and 26% of boys report being dissatisfied with their body shape/size
• 48% of 15 year old girls dieting to lose weight (1992)
• 27% of Ontario girls 12-18 years report disordered eating behaviours (vomiting, fasting, laxative use) (2001)

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Key features of anorexia nervosa

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• Refusal to maintain body weight at normal weight for age
• Intense fear of gaining weight
• amenorrhea
• distorted body image

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Key features of Bulimia nervosa

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• recurrent episodes of rapid consumption of a large amount of food in a discrete period of time
• use of laxatives or diuretics

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Binge Eating Disorder (BED)

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Binge eating, not followed by compensatory behaviours (2% of general population, 30% of dieting population)

Causation:

• Dietary restrictions leading to uncontrolled hunger
• role of food in their life: comfort, support, deal with stress, to feel numb,etc.

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Why In Adolescence?

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Life is overwhelming:

• many changes (physical, mental)
• struggling for own identity and independence
• Increased pressure: socially, academically, emotionally

Searching for control over stress

• food consumption and body weight can be controlled even when other things cannot