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A.2 Energy in Human Diets. IB Biology SL. A.2 Energy in human diets (Assessment Statements). A.2.1 Compare the energy content per 100 grams of carbohydrate, fat and protein. A.2.2 Compare the main dietary sources of energy in different ethnic groups.
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A.2 Energy in Human Diets IB Biology SL
A.2 Energy in human diets(Assessment Statements) A.2.1 Compare the energy content per 100 grams of carbohydrate, fat and protein. A.2.2 Compare the main dietary sources of energy in different ethnic groups. A.2.3 Explain the possible health consequences of diets rich in carbohydrates, fats and proteins. A.2.4 Outline the function of the appetite control center in the brain. A.2.5 Calculate body mass index (BMI) from the body mass and height of a person. BMI=(mass in kg)/(height in m)2. A.2.6 Distinguish, using the body mass index, between underweight, normal weight, overweight and obese. A.2.7 Outline the reasons for increasing rates of clinical obesity in some countries, including availability of cheap high-energy foods, large portion sizes, increasing use of vehicles for transport, and a change from active to sedentary occupations. A.2.8 Outline the consequences of anorexia nervosa.
The energy content of Nutrients?(Carbs, Proteins, Fats) Nutrients are chemical substances found in foods and used in the human body. • Humans are heterotrophs and, therefore, require energy from foods for cellular respiration in order to power all metabolic activities. FOOD CALORIES 1 kilocalorie (kcal) = 4.18 kilojoules (kj) (SI UNIT)
Recommended Daily Allowance kcal requirements are recommendations. Requirements can vary depending on size, gender, activity levels, health.
energy Storage of carbs, lipids & proteins • The main energy-storing bonds are those covalent bonds between carbon and hydrogen. • Lipids have a higher ratio of C-H bonds to C-O bonds than either carbs or proteins. One can eat lots of fresh fruits and vegetables without necessarily worrying about excess caloric intake because these items have only moderate amounts of carbs, little fat and are high in undigestible fiber.
Sources of Energy in Different ethnic groups Although there are over 50,000 edible plants in the world, rice, corn and wheat provide 60% of the world’s food energy needs. Staple diets vary by geographical region, culture and tradition.
Cassava (manioc, yuca, tapioca-root) • Cassava, sweet or bitter, (Manihotesculenta), a woody shrub native to South America. Grown in tropical/sub-tropical regions. • Third largest source of carbs in the tropics behind maize and rice. Carbs are derived from the root. Cassava is a poor source of protein. • Bitter varieties deter animals, pests, thieves. Unless properly prepared, Cassava can result in partial paralysis, cyanide intoxication, or goiters.
Appetite control system • Appetite control involves complex feedback loops from the nervous, endocrine and digestive systems. • The hypothalamus (at right) is involved in appetite control and feelings of satiety. Summary When the appetite control center receives hormonal/nervous stimuli: • Insulin, secreted by the pancreas when blood glucose levels are high. • PYY3-36 secreted by the small intestine, when food is present. • Leptin secreted by adipose tissue, with more secreted as amounts of stored fat increase.
Health Consequences of Diets Rich in carbohydrates • Consumption of large amounts of sugar can increase the risk of obesity, Type II diabetes and tooth decay. • Consumption of large amounts of starch can cause obesity – slow digestible starches, however, can prevent rapid changes in blood glucose levels. • Consumption of indigestible fibers in vegetables and fruits can lead to a feeling of satiety, slow glucose absorption, lower risks of certain types of colon cancers and
Consequences of Excess Fat Consumption Consumption of fats in large quantities carries a significant risk of: • Obesity • An increased risk of coronary heart/artery disease (positive correlation). Not all fats are created equal. • Polyunsaturated and monounsaturated fats are healthier than either trans fats and saturated fats. • Trans fats carry the greatest risks to human health.
Consequences of Excess Protein Consumption (>50 grams/day) • Consumption of large amounts of protein, either through high-protein/low carb diets or ‘muscle building powders’ may increase the risk of kidney stones (composed of uric acid), gout (inflammation in joints due to high levels of uric acid in the blood), osteoporosis, or impaired/reduced kidney function. • Excess protein consumption can ‘overwork’ not only the digestive system but also the liver and kidneys which can become hypertrophied. The kidneys will use calcium as a way to rid the body of excess protein, leaching the calcium from bone. Low Protein Diet May Extend Life-Span
Prader-Willi Syndrome • A rare genetic disorder associated in • seven genes on chromosome 15 are • deleted or unexpressed on the paternal • chromosome. • Affects between 1 in 25,000 and 1 in • 10,000 live births.
Body Mass Index (BMI) An imperfect scientific attempt to quantify whether or not an individual has the appropriate mass. WHO: “Body mass index (BMI) is a simple index of weight-for-height that is commonly used to clarify overweight and obesity in adults. It is defined as a person’s weight in kilograms divided by the square his/her height in meters (kg/m2).” BMI = (mass in kg)/(height in m)2 Reminder(s): • Weight (newtons) is a measure of the force pulling you down towards the ground. • Mass (kg) is the amount of matter you have in your body.
Example Example: What is the BMI of a 17 year old woman who is 1.65 m tall and has a mass of 60 kg? BMI = (mass in kg)/(height in m)2 BMI can not indicate how mass is distributed.
Obesity Source: World Health Organization (Fact Sheet & Charts) Key Facts: • Worldwide obesity has nearly double since 1980 • In 2008, more than 1.4 billion adults, 20 and older, were overweight. Of these, over 200 million men and nearly 300 million women were obese. • 35% of adults aged 20 and over were overweight in 2008, and 11% were obese. • 65% of the world’s population live in countries where overweight and obesity kills more people than underweight. • More than 40 million children under the age of five were overweight in 2011. • Obesity is preventable. Overweight and Obesity are defined as “abnormal or excessive fat accumulation that may impair health.” • A BMI greater than or equal to 25 is overweight. • A BMI greater than or equal to 30 is obesity.
Causes of Obesity and Overweight The fundamental cause of obesity and overweight is an energy imbalance between calories consumed and calories expended. Globally there has been: • An increased intake of energy-dense foods that are high in both fat and sugar. • An increase in physical inactivity due to the increasingly sedentary nature of many forms of work, changing modes of transportation, and increasing urbanization. • Ease of availability of cheap, highly-processedfoods as compared to relatively expensive fruits and vegetables. • Economic growth and cheaper foods have allowed for larger portion sizes. • Many tasks that were done in the home by hand are now done by machine. • The most popular pastimes have become less active (tv and video games have replaced active games/sports).
Health Consequences of Overweight and OBesity Overweight and obesity are the fifth leading risk for global deaths. Approximately 2.8 million people worldwide die each year as a result of being overweight or obese. • 44% of the diabetes burden, 23% of the ischemic attack heart disease burden and between 7% and 41% of certain cancer burdens are attributable to overweight and obesity. Health Consequences • Adverse metabolic effects on blood pressure, cholesterol, triglycerides, and insulin resistance. • Risks of coronary heart disease, ischemic stroke and type 2 diabetes mellitus increase steadily with increasing BMI. • Increased risk of cancer of the breast, colon, prostate, endometrium, kidney and gall bladder. • Increased risk of musculoskeletal disorders (osteoarthritis)
Treatments • Increased physical activity. • Diet counseling and diet modification to include more fruits and vegetables. • Psychological counseling. • Support Group Participation. • Gastric Bypass Surgery in extreme cases (when safe to do so). • Medications (Orlistat)
Anorexia Nervosa Being thin is not the same thing as being anorexic. Anorexia nervosa is a complex medical condition with many symptoms requiring medical care. Anorexia nervosa is a complex, serious, potentially life-threatening eating disorder and mental health condition characterized by self-starvation and excessive weight loss. It occurs in both males (.1%) and females (1%) considered to be healthy for their height and weight. About Anorexia Nervosa • Approximately 90-95% of anorexia nervosa sufferers are girls and women. • Between 0.5–1% of American women suffer from anorexia nervosa. • Anorexia nervosa is one of the most common psychiatric diagnoses in young women. • Between 5-20% of individuals struggling with anorexia nervosa will die. The probabilities of death increases within that range depending on the length of the condition. • Anorexia nervosa has one of the highest death rates of any mental health condition. • Anorexia nervosa typically appears in early to mid-adolescence.
Causes There is no single cause for anorexia. Most experts believe the condition is caused by a combination of psychological, environmental and biologicalfactors, which lead to a destructive cycle of behavior. Psychological (Personality) Risk Factors: • a tendency towards depression/anxiety, poor reaction to stress, excessive worrying and feeling doubtful/scared about the future, perfectionism, inhibition, feelings of obsession and compulsion. Environmental Risk Factors: • Stressful life events, abuse, pressures at school/home, difficult family relationships, complex hormonal changes during puberty, Western media ideals of men/women. Biological Risk Factors (Hypotheses): • ‘Appetite-Reward ‘pathway problems involving the hypothalamus. • Due to hormonal imbalances and potential sensitivity to the amino acid tryptophan, feelings of anxiety can be generated in people when they eat. • At the same time, starving themselves and excessive exercise lowers levels of tryptophan – making the person calmer and more relaxed.
Symptoms & Warning Signs of Anorexia Nervosa Eating disorder experts have found that prompt attention and intensive treatment to the signs and symptoms of anorexia nervosa can significantly improve chances of recovery. Symptoms: • Inadequate food intake leading to visible weight loss. • Intense fear of weight gain; obsession with weight and persistent behaviors to prevent weight gain. • Self-esteem overly related to body image. • Inability to appreciated the severity of the situation. • Binge-Eating/Purging Type involves binge eating and/or purging behaviors over the last three months. • Restricting Type does not involve binge eating or purging. Warning Signs: • Dramatic weight loss, preoccupation with food, calories, fat grams and dieting, Refusal to eat certain foods, Denial of hunger, Anxiety about gaining weight, Frequent comments about body image, Avoiding mealtimes, Development of food rituals, Withdrawal from family/friends, Excessive and rigid exercise routines –despite weather, fatigue, or injury, Using pills to urinate or have bowel movements
Health Consequences The most serious consequence of anorexia nervosa is death. Anorexics who go untreated can essentially starve themselves to death. Death occurs in 6% - 20% of cases. Early diagnosis and treatment is essential.
Health Consequences • An increased risk of very severe complications and health consequences that can be permanent. • Poor circulation and cardiovascular problems due to weakened heart muscle. • Coronary heart disease and irregular heartbeat/arrhythmia (due to low potassium levels). • Imbalance of minerals in the blood such as potassium, calcium and sodium. • Other complications include low blood pressure (hypotension), Anemia (low iron count), Dental problems (tooth decay), Low blood sugar levels (hypoglycemia), Acute Kidney (renal) failure (due to severe dehydration), Liver damage, Heart failure, Osteoporosis/fragile bones, Loss of muscle strength, Lose of sex drive (libido)/Erectile dysfunction in men, Growth of a downy layer of hair called lanugo all over the body (in order to keep the body warm), Fainting/fatigue/weakness and Dry hair/skin with hair loss. Anorexia during pregnancy can cause a miscarriage, premature birth, low-birthweight baby, need for a caesarean section.
Treatments The severity of the condition will call for different treatment protocols but may include: • Consultation: With your physician and possibly a psychiatrist, counselor, psychologist, dentist (if vomiting is part of the disorder), nurse, or dietician. • Psychological Treatment: Cognitive behavioral/analytic therapy, family therapy or interpersonal therapy. • Medication in Combination with nutritional supplements and counseling: Olanzapine, SSRIs (Selective Serotonin Reuptake Inhibitors. • Compulsory Treatment and/or Hospital Stays (inpatient/outpatient). • Guidance so that the individual is encouraged to increase social activities, reduce physical activity (exercise) and planned schedules for eating.
