Source: Lecture 20 | Biology, University of Michigan
Difficulty: Introductory. No prerequisites beyond general nutrition awareness.
College students commonly fall short on calcium, iron, and fibre while consuming too much fast food, processed food, and sugar-sweetened beverages. Eating disorders affect both men and women (20% of women and 10% of men among college students) and arise from a complex mix of genetics, psychology, social norms, and past dieting behaviours. Having a genetic predisposition does not guarantee you will develop an eating disorder, but it does increase susceptibility.
Anorexia nervosa
The least common of the three major eating disorders, characterised by excessive dietary restriction leading to severe weight loss, intense fear of gaining weight despite being underweight, and a lack of recognition of the dangers of low body weight. In simple terms, a person starves themselves and cannot see how thin they have become.
Bulimia nervosa
An eating disorder affecting 1 to 2% of Americans, characterised by bingeing on large amounts of food with a feeling of loss of control, followed by compensatory behaviours (vomiting, laxative use, excessive exercise, or fasting) to prevent weight gain. These behaviours occur at least once per week for 3 months.
Amenorrhoea
Cessation of menstrual periods. A consequence of anorexia nervosa and a component of the female athlete triad.
Satiation and satiety
See Lectures 18/19 notes for full definitions. Both are relevant to understanding how disrupted eating patterns alter hunger signals.
Food choice factors
The six categories of influence on what people eat: biological (hunger, taste, pleasure), personal experience (preferences, aversions, familiarity), individual (perceptions, beliefs, attitudes, motivations, knowledge, skills, values), social/cultural (culture norms, social norms, setting, context), psychological (mood, stress), and environmental (cost, accessibility, convenience, advertising).
Biological: hunger, taste, pleasure
Personal experience: preferences, aversions, familiarity
Individual: perceptions, beliefs, attitudes, motivations, knowledge, skills, values
Social and cultural: culture norms, social norms, social setting (where you eat), social context (who you eat with)
Psychological: mood, stress
Environmental: cost, accessibility, convenience, advertising
Many young adults consume more fast food, processed food, and sugar-sweetened beverages than recommended, and fewer vegetables, fruits, whole grains, and milk.
Calcium:
Adult bone mass is still being formed
RDA for ages 14 to 18: 1,300 mg
RDA for ages 19+: 1,000 mg
Should increase intake of milk and dark green leafy vegetables
Iron:
RDA for males 19+: 8 mg
RDA for females 19 to 50: 15 mg
Iron deficiency is high in women, may cause iron deficiency anaemia and impair cognitive function
Fibre:
RDA for males 19 to 50: 38 g
RDA for females 19 to 50: 25 g
NHANES: many young adults get less than 50% of recommended fibre
Unhealthy and abnormal relationships with food
Rise in response to stressors or traumatic events
Increasing among college students: 20% of women, 10% of men
Both men and women, girls and boys are affected
Associated with emotional and psychological issues
Least common of the three eating disorders
Characterised by:
Excessive dietary restriction leading to severe weight loss
Fear of gaining weight, despite being significantly underweight
Persistent lack of recognition about dangers of current low body weight
Body weight and shape extremely important to self-worth
Warning signs: preoccupation with dieting and body weight, severe anxiety about gaining weight, dramatic weight loss, self-esteem tied to body image, withdrawal from friends/family, excessive exercise
1 to 2% of Americans
Characterised by:
Bingeing on large amounts of food with loss of control and guilt/shame
Followed by compensatory behaviours: vomiting, laxative use, excessive exercise, excessive fasting
Behaviours occur at least 1 time per week for 3 months
Warning signs: evidence of bingeing, purging behaviours, diet pills and laxatives, staining of teeth, sore throat, withdrawal from family/friends
Can be life-threatening; affects quality of life, relationships, daily functioning
Anorexia nervosa: dehydration, fatigue, low body temperature, hair loss, demineralisation of bone, cessation of menstruation, low blood pressure, reduction of cardiac muscle
Bulimia nervosa: electrolyte imbalances (potentially life-threatening cardiac arrhythmias), self-induced vomiting leading to dehydration, teeth erosion, and oesophageal damage
Genetics and predisposition
Psychological and personality issues
Social norms and cultural environmental factors
Lack of self-esteem
Past dieting behaviours
Cultural emphasis on thinness
Eating disorders DO have genetic components
Inheriting DNA variations associated with bulimia does NOT mean you will develop bulimia
You are more susceptible but will not necessarily develop the disorder
Research: search for DNA variations associated with eating disorders; brain imaging studies
Students often think eating disorders only affect women. Both men and women are affected (20% of college women, 10% of college men).
Students sometimes believe that inheriting DNA variations associated with an eating disorder means you will develop it. Genetic predisposition increases susceptibility but does not determine outcome.
Students may assume anorexia is the most common eating disorder. It is the least common of the three.
⚠️ "If you inherit DNA variations associated with bulimia, you will develop bulimia" is FALSE. Genetic components increase susceptibility, not certainty.
⚠️ Know the RDAs: calcium (1,300 mg for 14 to 18; 1,000 mg for 19+), iron (8 mg males 19+; 15 mg females 19 to 50), fibre (38 g males; 25 g females).
⚠️ Anorexia nervosa is the least common of the three eating disorders.
⚠️ Bulimia diagnosis requires compensatory behaviours at least 1 time per week for 3 months.
⚠️ Know the six categories of food choice factors.
True or False: If you inherit DNA variations associated with bulimia, you will develop bulimia. (False)
Fill in the blank: The RDA for calcium for adults 19+ is _____ mg. (1,000)
True or False: Anorexia nervosa is the most common eating disorder. (False, it is the least common)
Fill in the blank: Bulimia nervosa is characterised by bingeing followed by _______ behaviours. (compensatory)
True or False: Only women are affected by eating disorders. (False)
Q: True or False: If you inherit DNA variations associated with bulimia, you will develop bulimia.
A: False. Eating disorders have genetic components that increase susceptibility, but inheriting the variations does not guarantee development of the disorder.
Q: Name three nutrients of concern for college students and their RDAs for young adult females.
A: Calcium (1,000 mg for ages 19+), iron (15 mg for females 19 to 50), and fibre (25 g for females 19 to 50).
Q: What are three warning signs of bulimia nervosa?
A: Evidence of bingeing, evidence of purging behaviours, staining of teeth, use of diet pills/laxatives, sore throat, withdrawal from family and friends (any three).
Q: Name three health consequences of anorexia nervosa.
A: Dehydration, fatigue, low body temperature, hair loss, demineralisation of bone, cessation of menstruation, low blood pressure, reduction of cardiac muscle (any three).
Eating disorders connect to the female athlete triad discussed in Lecture 17 (Exercise and Health), where disordered eating is one of three interlinked conditions. The hunger hormones (ghrelin and leptin) from Lectures 18/19 help explain why disrupted eating patterns are difficult to reverse. Nutrient deficiencies discussed here (calcium, iron) also appear in Lecture 16 (Dietary Supplements), where supplementation recommendations target exactly these gaps.
Eating disorders, anorexia nervosa, bulimia nervosa, binge eating, college nutrition, calcium RDA, iron RDA, fibre RDA, amenorrhoea, food choice factors, biological factors in eating, social factors in eating, environmental factors in eating, disordered eating, body image, self-esteem, compensatory behaviours, purging, laxative use, iron deficiency anaemia, cognitive function, nutrient gaps in young adults