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A history of fad diets. Which diets are designed for weight loss?. Which diets have a scientific basis?. You are what you eat!. When food is digested its components enter the blood. carbohydrate. glucose. fat. fatty acids + glycerol. protein. amino acids.
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A history of fad diets Which diets are designed for weight loss? Which diets have a scientific basis?
You are what you eat! When food is digested its components enter the blood. carbohydrate glucose fat fatty acids + glycerol protein amino acids Molecules used for growth and repairbecome part of the body. Those used as energy sources are lost as CO2 and H2O.
membrane: fats and carbohydrate nucleus: protein cytoplasm: protein and water What are cells made from? Different nutrients are incorporated into each part of a cell:
You are what you eat! What could this food label represent? A human!
Dietary guidelines vitamins and minerals (1%) protein (14%) carbohydrate (50%) fat (35%) The amount of each type of nutrient a person needs varies between individuals. What factors might affect how much a person needs?
Recommended daily allowance (RDA) of protein (g) = 0.75 x body mass (kg) Lack of protein Proteins in meat and fish are called first-class proteins because they contain all the essential amino acids that humans need in their diet. What is the RDA of protein for a 60kg student? RDA = 0.75 x 60kg = 45grams A protein deficiency illness called Kwashiorkor can cause a swollen belly and weak immune system, and is common in developing countries.
Metabolic rate is the rate at which cells uses energy, and this varies between individuals. Why does metabolic rate increase during exercise and cold weather? Why do some people need more food? Metabolism is the series of chemical reactions or ‘life processes’ in the body. Different amounts of energy are used in different life processes. digestion (10%) exercise andwarmth (20%) growth andrepair (70%)
Enzymes at work Enzymes digest food in the mouth, stomach and smallintestine. Enzymes break down large food molecules into smaller ones that can be absorbed by the blood. This is called chemical digestion. Different types of food are broken down by different enzymes.
Helping enzymes Enzymes are not the only substances involved in chemical digestion. Hydrochloric acid in the stomach provides the right conditions for protease enzymes to break down protein. Bile is a substance produced by the liver and stored in the gall bladder. It helps the digestion of fats by turning them into small droplets. This is called emulsification. How does this help lipase enzymes? The smaller droplets have a larger surface area, which speeds up the rate at which lipase digests the fat.
BMI = body mass (kg) (height)2 (m) BMI Conclusion Gloria: 1.45m and 66kg <20 underweight BMI = 31 20-25 normal Zak: 1.85m and 66kg 25-30 overweight BMI = 19 >30 obese What is BMI? Body Mass Index (BMI) measures the relative amounts of fat and muscle in the body. What are their health risks? Obese people have an increased risk of arthritis, diabetes and heart disease. People who are underweight tend to have poor immune systems and often get ill.
Are you right for your height? In 2002, 22% of boys and 28% of girls aged 2-15 in the UK were overweight or obese. Statistics show that obesity levels, among both young people and adults, are rising. Calculating a person’s BMI can be useful, but the formula can overestimate the proportion of body fat in people who are muscular. This is because muscle is denser than fat. This means it is helpful to use extra measures to help judge how healthy a person is, such as waist circumference.
What is blood pressure? Blood pressure is a measure of the pressure exerted by the blood against artery walls. Blood pressure varies with: • heartbeat strength • health • blood volume • age. • fitness Blood pressure is measured as two numbers, e.g. 120/80. What do these numbers show? The numbers show pressure readings in mm of mercury.
Systolic and diastolic “Blood pressure one-twenty over eighty.” The big number (‘120’) is the systolic pressure. This is the blood pressure during a heartbeat. The small number (‘8’) is the diastolic pressure. This is the blood pressurein-between heartbeats.
How does blood pressure affect health? Age Systolic Diastolic 10 80-100 60 15 90-110 60 20 110-125 70 40 130-150 80 High blood pressure can make blood vessels more likely to burst, and can cause strokes and kidney damage. Low blood pressure can cause dizziness, fainting and poor circulation. The older you get, the higher your blood pressure naturally becomes. Kevin is 38 years old and his blood pressure is 180/90. What advice would you give him?
Lifestyle assessment Kevin’s GP quizzed him about his lifestyle, tested his blood and referred him to a health centre. Excess salt is known to increase blood pressure in about 30% of the population. What else could Kevin do to improve his health?
Health and fitness Health and physical fitness are different. • A healthy person is free from disease or abnormality. • A fit person has good cardiorespiratory, aerobic and muscular endurance. Kevin’s GP wants his cardiovascular fitness to improve so that he puts less strain on his body. His personal trainer wants other sorts of fitness to improve. What types of exercise should Kevin do?
What is wrong with fast food? Fast food and takeaways such as curries, burgers and pizzas are high in unhealthy nutrients such as saturated animal fats,sugarandsalt. Fast food usually contains very little fibre, vitamins, minerals or unsaturated vegetable oils, which are important for a health diet.
What is cholesterol? Cholesterol is a lipid found in cell membranes and is used in the production of hormones and bile. Cholesterol is transported in the blood by molecules called lipoproteins, of which there are two types: • high-density lipoprotein (HDL): often called ‘good cholesterol’ • low-density lipoprotein (LDL): often called ‘bad cholesterol’. Cholesterol levels depend on diet and genes, but high levels of LDL have been linked to eating lots of saturated fats and few mono/polyunsaturated fats.
Good and bad cholesterol How do ‘good’ and ‘bad’ cholesterol affect a person’s health?
Cholesterol and heart disease Why is LDL called ‘bad cholesterol’? Excess LDL is deposited on the walls of blood vessels, which can lead to clots in the arteries. This can starve the heart of oxygen and cause heart disease. Why is HDL called ‘good cholesterol’? HDL returns cholesterol to the liver where it is metabolized. The risk of heart disease may be reduced by: • lowering blood cholesterol • eating more HDL than LDL • gentle daily exercise.
Taking action Kevin’s blood test showed high cholesterol, but not high enough to require drug therapy to reduce it. This margarine claims to cut blood cholesterol by 10%, but it costs four times as much as normal margarine. Should Kevin buy the margarine?What extra information would help him decide?
Yes! People should be allowed to self-medicate. No! People with normal cholesterol might take them and they wouldn’t be checked for side-effects like liver damage. What are statins? The plant extracts in margarine that lower cholesterol are less effective than cholesterol-lowering drugs called statins.Should these drugs be available without a prescription? What do you think?
Glossary (1/2) • blood pressure –The pressure in the arteries during and between contractions of the heart. • body mass index– A measure of a person’s weight in relation to their height. • chemical digestion – The process of breaking large food molecules into smaller ones using enzymes. • fitness–Strength, stamina, flexibility, agility, speed and cardiovascular efficiency. • health– Freedom from disease and injury. • heart disease–An abnormal condition of the heart or the arteries that supply the heart.
Glossary (2/2) • lipoproteins – Molecules that carry cholesterol in the blood and which are either high density or low density. • metabolic rate–A measure of how fast chemical reactions occur in cells. • obese– A person who is very overweight and has a BMI of over 30. • physical digestion– The breaking up of pieces of food by chewing it in the mouth and churning it in the stomach. • saturated –A type of animal fat that raises blood cholesterol levels and increases the risk of heart disease. • unsaturated –A type of fat from vegetable and fish oils that helps lower blood cholesterol levels and reduce the risk of heart disease.
