Introduction to Nutrition and Metabolism PDF

Introduction to Nutrition and Metabolism Bronwen Dalziel Learning Objectives Define the measurements used to quantify energy Discuss how the body uses energy: BMR, thermogenesis, physical activity Define BMI and how it is calculated What this block is about Photo by Henley Design Studio on Unsplash...

Introduction to Nutrition and Metabolism Bronwen Dalziel Learning Objectives Define the measurements used to quantify energy Discuss how the body uses energy: BMR, thermogenesis, physical activity Define BMI and how it is calculated What this block is about Photo by Henley Design Studio on Unsplash Photo by SwapnIl Dwivedi on Unsplash How do we turn food into energy? How do we use energy? How do we store energy? How do we convert the stored energy in our body back into energy? How do enzymes do this? What happens if we eat too much? Or too little? What nutrients do we need from food? What hormones are involved in regulating the nutrients that we eat? What happens when these pathways are disrupted? Energy ATP - energy currency of the cell Energy is stored in the covalent bonds between phosphate groups https://www.sciencelearn.org.nz/images/2267-unlocking-atp-energy ATP is converted to ADP and Pi, releasing energy ATP is energy carrier, not energy store; continually made and broken down (ATP cycle) Examples – ATP used for work Chemical e.g. making new proteins for the body Transport e.g. Sodium Potassium Pump across membrane Mechanical e.g. moving your muscles Energy units Calorie is (originally) the unit of energy in nutrition 1 calorie = amount of heat required to raise the temperature of H2O by 1oC (from 14.5oC to 15.5oC) Nutritionally the kilocalorie is used (= 1000 calories) 1 Joule = energy used when a mass of 1 kg is moved through 1 m by a force of 1 Newton 1 kcal = 4.18 kJ Australian nutrition guidelines use the kilojoule as the official measure of energy in food and drink Where does our energy come from? Macronutrients Substrate Form of Storage Pool Size Tissue Energy Density* Autoregulation Carbohydrate Glycogen Small Liver, Muscle ~17 Accurate Fat Triglycerides Moderate- Adipose Tissue ~37 Large (unlimited) Poor Protein Protein Moderate (limited) Accurate Lean Tissue ~17 *As stored in tissues (kJ/g) Modified from Table 6.1, Geissler and Powers (2017) Human Nutrition, pg 117 Alcohol is also a source of energy – metabolised in the liver to yield energy Food into Energy Digestion Physical (mechanical): food broken into smaller particles in the mouth Chemical: digestive enzymes change food into simple, soluble forms that can be absorbed Metabolic: nutrients are used at the cellular level for basic life processes Body Composition - chemical Diagrammatic representation of the body composition of a normal adult male weighing 70kg. Only fat, protein and glycogen contribute to the energy stores of the body Muscle mass is the predicted weight of muscle in your body and includes skeletal, smooth and cardiac muscle Figure 5.1 Geissler and Powers (2017) Human Nutrition, pg 97 Measuring body composition Skinfold thickness Bioelectrical impedance Underwater weighing Dual energy x-ray absorption (DEXA) Not preferred in routine clinical practice Technically demanding Expensive Intrusive Rely on complex technologies Not easily available Difficult to standardise https://weightology.net/the-pitfalls-of-body-fat-measurement-part-5-skinfolds/ https://www.j-sens-sens-syst.net/6/303/2017/jsss-6-303-2017.pdf; http://tsukinegradprogram.blogspot.com/2014/11/body-composition-bioelectrical.html https://dapa-toolkit.mrc.ac.uk/anthropometry/objective-methods/hydrostatic-underwater-weighing; https://en.wikipedia.org/wiki/Dual-energy_X-ray_absorptiometry#/media/File:DEXA_scanner_in_use_ALSPAC.jpg Body Fat % Based on American Council on Exercise (ACE) Body Fat Chart Energy balance Increasing weight Energy intake > Energy expend iture = Energy stores Decreasing weight Energy intake < Energy expenditure = Energy stores Energy Expenditure Made of 3 components 1. Basal Metabolic Rate 2. Physical Activity 3. Thermogenesis (increase in energy expenditure in response to certain stimuli including food, cold, stress, and drugs) Basal Metabolic Rate (BMR) The energy needed for the work of vital functions § cell and protein turnover § maintenance of electrolyte equilibrium across membranes § respiratory and cardiovascular functions Largest component (70 - 80% ) of daily energy expenditure Most important determinants of BMR: Body size (larger adults have a higher BMR) Fat Free Mass (FFM) or lean muscle tissue (needs more energy) Basal Metabolic Rate (BMR) Other determinants of BMR § Fasting can slow metabolism § Growth – children have higher energy demands § Genetic predisposition § Hormonal imbalances (e.g. thyroid disorders) On average men have a higher BMR and FFM than women and older people have a lower BMR and FFM than young adults BMR in Tissues and Organs Contribution of different tissues and organs to basal metabolic rate (BMR) of a reference man of 70 kg Weight of tissue Organ/tissue metabolic rate kg % body weight MJ/kg/day MJ/day % BMR Liver 1.8 2.6 0.84 1.51 21 Brain 1.4 2.0 1.00 1.41 20 Heart 0.33 0.5 1.84 0.61 9 Kidney 0.31 0.4 1.84 0.57 8 Muscle 28.0 40 0.054 1.52 22 15 21.4 0.019 0.28 4 23.16 33.1 0.049 1.13 16 70 100 0.1 7.03 100 Adipose tissue Miscellaneous by difference (e.g. skin, intestine, bone) Whole body Table 6.4, Geissler and Powers (2017) Human Nutrition, pg 123 How much energy do you need for your BMR? Female – 165 cm Male – 180 cm 30 40 45 1307 1250 1204 55 1402 1346 1299 65 1498 1442 1395 65 1739 1658 1590 75 1876 1795 1727 85 2014 1933 1865 Table in Calories BMR calculator: http://www.mydr.com.au/tools/basal-energy-calculator Female 165cm 18 Male 180cm Weight (kg) Age BMR - Summary Males have a higher BMR than Females Younger individuals have a higher BMR than older individuals Heavier individuals have a higher BMR than lighter individuals Physical Activity Energy expenditure depends on type, intensity & time spent during the activity Accounts for approx. 10-15% of energy expenditure https://caloriecontrol.org/healthy-weight-tool-kit/get-moving-calculator/ http://www.exercise-to-a-healthier-life.com/exercise-overweight.html 73 kg 91 kg 109 kg Thermogenesis Increase in energy expenditure in response to certain stimuli including food, cold, stress, and drugs The body generates heat by increasing the metabolic rate above normal Isometric: increase in muscle tension Psychological: stimulation of adrenaline secretion Cold-induced: raised metabolic rate at low temps Diet-induced: heat production increases after eating Drug-induced: heat production increases after taking drugs NEAT Good to know: Non-exercise activity thermogenesis (NEAT) Energy expended for everything we do that is not sleeping, eating or sports-like exercise - Walking around supermarket - Typing - Fidgeting The total impact of a lots of these actions culminate in an individual's daily NEAT. NEAT explains a vast majority of an individual's non-resting energy needs. NEAT increases with overfeeding and decreases with underfeeding. Could explain some of the differences in how people deal with excess energy in food (and maintain body weight) NEAT Ways to Increase NEAT 1.Take the stairs 2.Get a standing desk 3.Take phone calls standing 4.Park your car further away from your destination 5.Fidget – wiggle your legs while you watch a lecture 6.Housework! Note: Thermogenesis and NEAT will increase resting metabolic rate (RMR) but not BMR Energy Requirements Age (years) Male* Female^ 19-30 10300 8400 31-50 9900 8000 51-70 9100 7600 70+ 8300 7200 values in kJ *estimated energy intake for male 180cm tall, 71.3kg ^estimated energy intake for female 170cm tall, 63.6kg Energy demands also depend on activities of an individual http://www.nutritionaustralia.org/national/resource/balancing-energy-and-out how to understand food labels What to look for… Don’t rely on health claims on labels as your guide. Instead learn a few simple label reading tips to choose healthy foods and drinks, for yourself. You can also use the label to help you lose weight by limiting foods that are high in energy per serve. Nutrition Information Total Fat Generally choose foods with less than 10g per 100g. For milk, yogurt and icecream, choose less than 2g per 100g. For cheese, choose less than 15g per 100g. Saturated Fat Aim for the lowest, per 100g. Less than 3g per 100g is best. Other names for ingredients high in saturated fat: Animal fat/oil, beef fat, butter, chocolate, milk solids, coconut, coconut oil/milk/cream, copha, cream, ghee, dripping, lard, suet, palm oil, sour cream, vegetable shortening. Servings per package – 16 Serving size – 30g (2/3 cup) 100g Column and Serving Size Per serve Per 100g Energy 432kJ 1441kJ Protein 2.8g 9.3g Total 0.4g 1.2g Saturated 0.1g 0.3g Fat If comparing nutrients in similar food products use the per 100g column. If calculating how much of a nutrient, or how many kilojoules you will actually eat, use the per serve column. But check whether your portion size is the same as the serve size. Energy Check how many kJ per serve to decide how much is a serve of a ‘discretionary’ food, which has 600kJ per serve. Sugars Carbohydrate Total 18.9g 62.9g Sugars 3.5g 11.8g Fibre Fibre 6.4g 21.2g Not all labels include fibre. Choose breads and cereals with 3g or more per serve Sodium 65mg 215mg Ingredients: Cereals (76%) (wheat, oatbran, barley), psyllium husk (11%), sugar, rice, malt extract, honey, salt, vitamins. Ingredients Listed from greatest to smallest by weight. Use this to check the first three ingredients for items high in saturated fat, sodium (salt) or added sugar. Avoiding sugar completely is not necessary, but try to avoid larger amounts of added sugars. If sugar content per 100g is more than 15g, check that sugar (or alternative names for added sugar) is not listed high on the ingredient list. Other names for added sugar: Dextrose, fructose, glucose, golden syrup, honey, maple syrup, sucrose, malt, maltose, lactose, brown sugar, caster sugar, maple syrup, raw sugar, sucrose. Sodium (Salt) Choose lower sodium options among similar foods. Food with less than 400mg per 100g are good, and less than 120mg per 100g is best. Other names for high salt ingredients: Baking powder, celery salt, garlic salt, meat/yeast extract, monosodium glutamate, (MSG), onion salt, rock salt, sea salt, sodium, sodium ascorbate, sodium bicarbonate, sodium nitrate/nitrite, stock cubes, vegetable salt. Body Mass Index (BMI) Body mass index (BMI) is a measure that can help predict risk of developing disease. It uses a person’s height and weight https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm http://healthyweight.health.gov.au/wps/portal/Home/get-started/are-you-a-healthy-weight/bmi weight (kg) height m2 Why use BMI? As a population wide tool it predicts morbidity and mortality BMI Classifications BMI (kg/m2) 40.0 Very obese 30.0-40.0 Obese 25-29.9 Overweight 18.5-24.9 Normal 17-18.49 Mild energy deficiency 16-16.9 Moderate chronic energy deficiency less than 16.0 Severe chronic energy deficiency For individual it is better to use a combination of tools. Limitations of BMI Is used differently for children Athletes/muscular build (overweight) Different ethnicities (Asian - lower; Polynesian higher) Less accurate for pregnant women, elderly, people with eating disorders, physical disability BMI only a proxy for total fat BMI does not distinguish between different types of fat distribution Calculate your BMI Or BMI Calculators: http://www.whathealth.com/bmi/chart-metric.html http://healthyweight.health.gov.au/wps/portal/Home/helping-hand/bmi https://www.gethealthynsw.com.au/healthier-you/tools-and-calculators/bmi-calculator/ BMI in adults examples Middle aged sedate Caucasian woman 168cm 76kg BMI = 26.92 (overweight category) Middle aged Polynesian male 173cm 76kg BMI = 25.4 (healthy weight) Waist to Height Ratio Better predictor of health http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4223160/ BMI in Children Children are healthiest if they stay within a certain weight range for their height and age as they grow. This is called a healthy weight for their age. BMI-for-age charts developed by the US Centres for Disease Control and Prevention (CDC 2000) are used. These charts are recommended for use in Australian children aged 2 to 18 years. Weight Category Percentile Range Below a healthy weight Less than the 5th percentile Healthy Weight 5th percentile to less than the 85th percentile Above a healthy weight 85th to less than the 95th percentile Well above a healthy weight Equal to or greater than the 95th percentile BMI in Children Height 115cm (tall for age) Weight 20kg (average weight) BMI 15.1 http://pro.healthykids.nsw.gov.au/calculator/ BMI in Children Height 105cm (short for age) Weight 20kg (average weight) BMI 18.1 Healthy body weight Balanced diet Achieving Energy Balance – calorie control, physical activity Summary Energy is required to perform various functions in the body and is measured in kilocalories or joules Our body derives energy from food macronutrients (carbohydrates, fats and proteins) The body expends energy in 3 ways: BMR, Physical Activity & Thermogenesis BMI is a measure of body fat based on height and weight L inks http://www.nutritionaustralia.org/national/resource/balancing-energyand-out https://www.eatforhealth.gov.au/eat-health-calculators http://healthyweight.health.gov.au/wps/portal/Home/get-started/areyou-a-healthy-weight/ https://www.healthdirect.gov.au/body-mass-index-bmi-and-waistcircumference Contact Dr Bronwen Dalziel School of Medicine Western Sydney University [email protected]