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What is a growth spurt?
Peak high velocity: highest nutritional needs
how much height and weight do you gain during growth spurt?
accretion of 20% of adult and 50% of weight
why is it difficult to estimate energy and protein requirements for individuals during growth spurt?
high inter-individual variability in growth rate
What id the only period post-utero in which growth velocity increases?
What minerals are needed in twice the amount during growth spurt?
2x higher incorporation of Ca, Mg, Zn, Fe into bones as compared to non-growth spurt period
how are nutrient needs determined during growth spurt?
-Intensity and extent of the pubertal growth spurt
- -Gender differences in growth and body composition changes,
- -Differences among individuals in terms of the timing of the pubertal growth spurt
What does SMR stand for?
Sexual Maturity Rating
what is the best guide for growth and development?
What is the SMR based on?
Based on the development of secondary sexual characteristics (eg. pubic hair, breasts etc)
How is maturation not predictable?
Predictable sequence, but timing of initiation and movement from stage to stage varies
why are growth charts not accurate during puberty?
crossing of growth channels (area between 2 percentiles) during pubertal growth
What is SMR1?
- Rapid growth but no discernable sexual changes
- 0.2-1.2 years in females, 0.5-2 years in males
What SMR stage does bone mass peak?
- SMR2 in females
- SMR3-4 in males
What happens during SMR2 in females and SMR 3-4 in males?
Timing of bone mass ad skeletal growth with 40% of peak bone mass
When do males and females experience peak weight accumulation?
- Females: 6-9 months prior to peak height velocity (gain 42% of adult mass)
- Males: at same time as peak height velocity (51% of adult mass)
When does lean body mass accumulation occur?
- Females: peaks at SMR 3-4
- Males: SMR 5, after stature gain is complete
When does late puberty occur?
- Females: 14-16 years
- Males: 14-17 years
When does menarche occur?
- Around 12 years
- Tends to occur 1 year after breast development
- At the deceleration phase of growth--> later menses associated with longer period of growth, greater height
For males does growth stop after sexual maturation has ended?
No, growth can continue after sexual maturation has ended
What causes growth spurt?
Combined action of several hormones (growth hormone, testosterone, adrenal androgens)
Why is achieving bone mass in adolescence important?
Important to protect against osteoporosis
What happens to the epiphyses at the final stage of growth?
At final stage of skeletal growth epiphyses fuse with main portion of bone and growth ins stature ceases
What is epiphyses?
Rounded prominence separated from main part of bone by fibrous tissue and cartilage during skeletal growth
What nutrient does rapid height gain require?
Needs high intake of Ca (45% of total body Ca deposited in adolescence)
How many teens have adequate Ca intake?
15% of teen females and 53% of males have adequate Ca intake
How much of adult weight is reached in adolescence?
50% of adult weight is reached in adolesence
Why do males require higher amounts of nutrients and calories during growth spurts?
Because they gain more lean body mass which has a higher metabolic activity than fat
How much body fat do females age 18 have?
What is the critical body mass and body fat composition of females?
Critical body mass of 47.8kg (105 lbs) and body fat composition of 17% for onset of menses
Which type of people often have delayed menses?
- People with very low body fat
- Ballet dancers, anorexics, athletes
How many people are affected by eating disorders?
>1 million teens are affected by eating disorders (either under or overconsumption)
What are some factors that can affect eating disorders?
Sociocultural, Neurochemical and psychological actors
What can happen as a result of skipping breakfast?
Increased risk of greater food intake at subsequent meals, compulsive snacking
How can parenting practices cause eating disorders?
- Rigid parental behaviour and excessive permissiveness->greater risk of rebellion -> binges, food aversions, faddisms, purging and fasting behaviours
- Decreased family and increased peer influences
How does mass media influence eating disorders?
Promote anorexic body images, soft drinks, low nutrient foods; use of foods to satisfy emotional and social needs
Why are fast foods bad?
Low nutrient and fiber content bug high sugar, sodium content
How can smoking influence eating disorders?
- Nicotine decreases food intake and increases weight loss
- Smoking eases hunger signals (animal studies) which can increase risk of nutrient deficiencies
- Quitting associated with mean increase of 10 lbs
What are some internal factors that can influence eating disorders?
- Multiple physiological changes (with new body image) --> altered eating behaviour to conform with body image style
- 70% of females 14-18 yrs have dieted (only 15% classified as obese)
- Increased risk of nutrient deficiencies and life-long risk of weight cycling
Why is there a general increase in adipose tissue during weight loss and gain?
- 10% drop is body weight leads to a 15% drop in BMR
- Changing back to normal diet leads to an increase in weight gain
- Loss of lean+adipose tissue during weight loss; predominant adipose tissue gain during weight gain
- Overal shift to increase adipose:lean tissue ratio
Are eating disorders more likely to occur in males or females?
Eating disorders are 20x more likely in teen females than males
How many teen males feel they need to gain weight?
60% of teen males feel they need to gain weight (only 25% are below average)
How does dependance on social opinion influence eating disorders?
- Increased need for independence--> more time spent away from home (development of more mature relationships with peers of both sexes)
- Increased risk of irregular eating habits. Snacks with high quality foods can be provided to overcome this
- Developing conceptual problem solving skills--> can exert more independent food choices
How many teens are obese?
10-20% of teensa re obese (>20% IBW or BMI>27)
What causes obesity?
- Complex mis of environmental ad genetic factors
- Estimated that genetics contributes 80% of the risk for obesity
- 20% caused by environment (laval university twin studies)
- 130 genes associated with obesity, controlling a wide variety of processes regulating food intake and energy metabolism
How do fluctuations in energy metabolism affect obesity?
- How quickly the fut lets the brain know that its full
- How effectively the body converts extra calories to fat
- Fidgeting (burns substantial amounts of calories)
- How much fuel the muscles need to carry out normal daily activities (small variation)
How does 15-20 weeks of exercise 5x per week change your body?
Aerobic adaptation resulting in stronger hearts and muscles and an increase in maximal oxygen uptake (increase efficiency in oxygen utilization by lungs, heart circulation)
Can genes alone lead to obesity?
No need combination with environmental conditions
How does childhood obesity affect people later in life?
No impaired socialization/long term psychological harm if they lose weight before adolescence
How do many teens attempt to combat obesity in adolescence?
- Try to restrict calories--> linear growth restriction, nutritional dwarfism (short stature, delayed puberty)
- Catchup growth only in 61% of teens upon nutritional rehabilitation
What are the diagnostic criteria of anorexia nervosa?
- No known medical psychiatric illness accounting for anorexia and weight loss
- Body weight 15029% below expected weight
- Intense fear of weight gain even when underweight
- Females: absence of at least 3 menstrual cycles
- Disturbed self image including denial of recognizing food needs, desired body image of extreme thinness
What are the 2 types of anorexia nervosa?
- Restrictive type- no purging behaviour
- Binging/purging type- binging followed by vomiting, diuretics or laxitives
What is the mortality rate of anorexia nervosa?
2-20% due to multiple organ system failure including electrolyte imbalance-> cardiovascular abnormalities (arrhythmia; inefficient heart pumping due to weakened heart muscle)
What are the GI symptoms of anorexia?
Similar to Chron's disease: diarrhea, cramping, fever
What is Wernicke's encephalopathy?
- Can be caused by anorexia
- Irreversible brain damage due to thiamin deficiency
What happens during muscle wasting as a result of anorexia?
Decrease in LBM, Decreased BMR, defective thermo-regulation and decreased muscle function
What are some changes in body functions characteristic of starvation?
- Dry skin
- Hirsutism (excessive body hair)
- Thin brittle dry hair, hair loss
- Dehydration and edema
What is osteopenia?
Decreased bone mass density 1-2.5SD below young adult mean leads to INCREASED risk of osteoporosis
What are some diagnostic criteria of bulimia?
- Binging twice a week followed by purging for 3 months
- Compensatory behaviour to prevent weight gain
- Distorted/ill-informed attitudes regarding food nutrition
- Compulsion to eat is not a response to hunger but a means to dull emotional states (depression, stress)
- Self evaluation according to body shape and weight; fear of gaining too much weight
What is binging?
Eating in a discrete period of time an excessive amount of food and a lack of control while eating
When does bulimia often occur?
Late adolescence of early adulthood, after a series of unsuccessful weight reducing diets
What type of people often resort to bulimia?
Outwardly successful and busy individuals with delay in psychosocial development into adulthood and are more easily frustrated individuals
What is non-purging type of bulimia called?
- Exercise or fasting
- Fasting accompanied by a depleted nutritional state
What are the health risks of bulimia?
- Irritation and infection of esophagus, salivary glands
- Erosion of teeth and dental caries
- Fluid and electrolyte imbalances
- Kidney injury (UTI)
- Increased risk of sub-clinical malnutrition
How does fluid and electrolyte imbalance caused by bulimia affect health?
- Abnormal heart rythyms
- Overuse of emetics, drugs used to induce vomiting
What are atypical eating disorders?
Eating disorders in teens which do not fit in pattern of other eating disorders such as pica or rumination disorders
How are eating disorders in teens treated?
- Specific approaches geared towards the psychology of adolescence
- Appeal to need for social acceptance in terms of good physical appearance resulting from good nutrition
- Replace distorted beliefs regarding weight and food intake
- Work together with teen to accommodate the need for independence
- Emphasize importance of breakfast