Nutrition 3210 Midterm Notes PDF - University of Guelph

lOMoARcPSD|30033153 Nutrition 3210 Midterm Notes Fundamentals of Nutrition FW (University of Guelph) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Sophia Medeiros ([email protected]) ...

lOMoARcPSD|30033153 Nutrition 3210 Midterm Notes Fundamentals of Nutrition FW (University of Guelph) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153 Nutrition 3210 Midterm Notes Introduction to Nutrition  Nutrition is the study of the processes by which organisms ingest, digest, absorb, transport, utilize and excrete food substances  Essential nutrient is a chemical that is required for metabolism, but cannot be synthesized or cannot be synthesized rapidly enough to meet the needs of an animal or human for one or more physiological functions  Nutrients are essential if: - Removing the nutrient from the diet causes a deficiency and decline in health - Putting the nutrient back into the diet corrects the problem and health will return - Take out = have a problem, put back = problem fixed Deficiency  Nutritional deficiency – occurs when a person’s nutrient intake consistently falls below the recommended requirement  Anemia = deficient in iron, folate and/or vitamin B12 - Not enough red blood cells to transport O2, important in key stages of development  Beriberi = deficient in Thiamine (B1) - Defective energy production, abnormalities in NS  Scurvy = deficient in Vitamin C - Defective collage production (important for structure), hemorrhaging & bleeding of the gums  Rickets = vitamin D deficiency - defective bone growth Estimating Nutrient Requirement  Deficiency  prevention of disease  nutritional requirement  ensure optimal health  eating enough of X so you aren’t not ‘deficient’ may prevent disease but doesn’t give you optimal health  early recommendations for nutritional requirement didn’t take into account differences in age, gender, body size physical activity  nutritional requirements can be estimated statistically - the estimated average requirement (EAR) is the amount of X nutrient that satisfies 50% of the populations end point (end point being proper growth, storage and health) - the recommended dietary allowance (RDA) is EDA + 2 standard deviations, and is the value of X which satisfies 98% of the populations end point  there is also an tolerable upper limit to nutrient intake, when you consume more than the upper limit the nutrient is in excess which also causes health problems Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153  dietary reference intake (DRI) is the set of reference values for specific nutrients (EAR, RDA and UL) - the DRI defines the EAR, RDA and UL for every nutrient Starvation  Minnesota starvation experiment: 3 months high cal. diet, 6 months low cal. diet, 3 months rehab  starvation led to weight loss, irritability, dizziness, tiredness, hair loss, reduced sex drive, depression and more  the effects of starvation can take more than a year to be reversed 4 characteristics of a nutritious dies  adequate: a diet that provides enough calories, essential nutrients and fibre to keep you healthy  moderate: ensuring you don’t consume excessive calories, or eat more of one food or food group than recommended  balanced: making sure you eat nutrient-dense foods, rather than nutrient-poor foods  varied: eating a wide selection of food to get the necessary nutrient Methods for studying nutrition  cell cultured models  animal models  epidemiological studies Nutrient Classes Organic (contains carbon) Inorganic  * Macronutrients: consume in large quantities  # micronutrients: consume in small quantities Carbohydrates (& fibre) * Minerals #  water is essential but is neither a macro or micro Lipid* Water nutrient Protein *  water makes up 60% of the body, lipids make up 20- Vitamins # 25%, protein 15%, vitamins & minerals 2%, carbs 0.5% Metabolism  metabolism = anabolism + catabolism  anabolism = building (simple  complex)  catabolism = breakdown (complex  simple) Water  Functions of water: - Solvent in biochemical reactions - Catabolism (hydrolysis) Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153 - Maintains vascular volume - Nutrient transport - Temperature regulation  adult require intake: 2.7L – 3.7L  20% of water comes from food  average intake of carbs: 250 -350 grams per day  fat: 60 – 80 grams per day  protein: 50-80 grams per day Water Toxicity  occurs when, water intake >> kidney’s ability to process (~0.9L per hour)  water is processed through the kidney where urine is made to be excreted)  hyponatremia = water / sodium imbalance - can occur from excessive fluid intake, under-replacement of sodium or both - hyponatremia is avoided with urination - hyponatremia causes CN edema and muscle weakness - can occur in elite athletes who consume large amount of water without enough electrolytes Proximate Analysis  food analysis is the development, application and study of analytical methods for characterizing foods and their constituents  why is knowing food composition important? - information about foods produces foods that are safe and nutritious and allows the consume to make informed decisions - government regulation: maintain quality food, ensure food industry makes safe foods, fair competition between companies, eliminate economic fraud - quality control: ensures food composition doesn’t change, characterize raw materials Nutrient Density  all foods are not created equal  caloric content does not predict nutrient content in foods  nutrient dense foods: have a high, nutritional value: caloric content is very high  empty calorie foods: have high calories and low nutrients Steps of Proximate Analysis 1) Moisture (water content)  To determine water content air dry the feed sample (dehydrate it)  % moisture = (weight loss / wet weigh sample) x 100%  % dry matter = 100 - % moisture  determining water content is important since: - water is weight, more weight = higher cost - moisture content plays a role in storage conditions, too much water a food spoils quickly, too little water and the food is less palatable - moisture dilutes energy and nutrients in food - moisture is important for optimum intake and performance of animals  sources of errors and limitations: - drying can remove other volatile compounds such as short chain fatty acids and some minerals  causing a slight under-estimation of dry weight  human food labels are based on wet weight, animal feed is more interested in dry matter 2) Ether extract (crude fat)  Run an ether extraction  creates a solution (liquid) phase and a residue phase  Remove the solution phase (which contains the lipids) and dry it out Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153  % crude fat = (weight of crude fat/wet weight of sample) x 100%  Potential sources of error / limitations: - Things other than lipids are soluble in the extract (e.g chlorophyll, resins and waxes are soluble in the ether extract but provide no nutritional value – they are not dietary fats) - This causes an over-estimation of crude fat  New method: the ether extract is ran through gas chromatography (instead of drying out), provides you with the amounts of specific dietary fats in the ether extract 3) Ash (mineral content)  The residue phase of the ether extraction is burned, the organic material burns off and all you are left with is ASH (the minerals/inorganic material)  Determining ASH content is important for: - Nutritional labelling - Quality and taste of food - Microbiological stability - Nutritional requirements - Manufacturer processing  % ASH = (weight of ASH / wet weight of sample) x 100%  Potential sources of error/limitations: - Volatile minerals may be lost when the residue is burned - This causes an underestimation of mineral content - There is not information about individual minerals (it is now mandatory for food labels to indicate Na content) 4) Nitrogen (crude protein)  Determine by Kjeldahl analysis of the dry matter  2 assumptions of Kjeldhal analysis: - all nitrogen is protein - all protein contains 16% nitrogen  3 main steps of Kjeldahl Analysis 1) digestion – dry food sample mixed with sulfuric acids, converting Nitrogen to ammonia 2) Distillation – separated ammonia 3) Titration – quantifies amount of ammonia  % crude protein = ( (Nitrogen in sample x 6.25)/ wet weight of sample) x 100% - 6.25 comes from the idea that all protein is 16% nitrogen - 100% (total protein) / 16% (nitrogen) = 6.25 - nitrogen x 6.25 = crude protein - midterm: could be given a different nitrogen content (not 16%) and would have to change the conversion factor  Potential sources of error/limitations - Assume all protein has 16% nitrogen (in reality it ranges from 13%-19%) - There are other sources of nitrogen that aren’t protein (nitrates, nitrites, urea, nucleic acids etc.)  this causes an over estimation of crude protein content 5) Crude fibre (fibre)  Take residue from ether extract: 1) Boil in acid 2) Take residue (what is not soluble in acid) and boil in alkali 3) Take residue (which consists of ASH and crude fibre) and ignite 4) You are left with ASH, must back calculate to get fibre Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153  % crude fibre = ((weight of ASH + crude fibre) – wt of ash)/wet weight of sample) x 100%  crude fibre dietary fibres  crude fibre is insoluble, dietary fire is both insoluble and soluble fibre  crude fibre is primarily cellulose and lignin, soluble fibres are mostly loos during the analysis process  Potential sources or error/limitations: - Unable to distinguish the different fibre components - Measuring crude fibre underestimates actual dietary fibres content by up to 50% - Dietary fibre includes cellulose, hemicellulose, pectin, mucildges, gums, lignin which are lost during analysis 6) Nitrogen Free Extract (NFE) = Digestible carbohydrates (CHO)  Estimates starch and sugar content  % NFE = 100 – (% moisture + % crude fat + % ASH + % crude protein, + % crude fibre)  potential sources of error/limitations: - NFE accumulates ALL of the ERRORs that exists for the other components General Notes of Proximate Analysis  No information on ‘digestibility of food/feed - Don’t know what is actually absorbed by the organism  No information of specific AA, minerals, lipids or carbohydrates  Still is the basis for food labelling and animal feed analysis Dietary Fibre  Dietary fibres are non-digestible complex carbs  Come from structural part of plants  INSOLUBLE FIRBES = cellulose, lignin, hemicellulose - Do not dissolve in water - Insoluble fibres remain intact through the intestinal tract - Insoluble fibres help move food along the digestive tract (reducing constipation, bloating etc.), they also help maintain the pH of the digestive tract helping the bacterial community survive  SOLUBLE FIRBES = pectin, gums, mucilage - dissolves in water - forms a gel - hangs onto other nutrients and slows down absorption (slowing down glucose absorption helps w type 2 diabetes, slowing down cholesterol absorption reduces risk for cardiovascular disease)  other fibre analyses that complements Proximate Analysis: 1) Van Soest Method 2) Southgate Method Van Soest Method of Fibre Analysis in Feeds  Detergent fibre analysis  Differentiates between the insoluble fibres - Cellulose & hemicellulose - Lignin (poorly fermented, prevents fermentation of other fibres) Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153  Determines fermentable and non-fermentable CHO  Important in agriculture applications  Poorly differentiates sugars, starches and soluble fibres Southgate Method of Fibre Analysis for Human Food Labels  Provides information about sugars, starches and various fibres  Used for human nutrition and food labels  Does not differentiate b/w various fibre components adequately, therefor NOT used is agriculture Digestive Systems Gastrointestinal Tract  Composed of the: - Mouth - Esophagus - Stomach (monogastric = 1 stomach, avian = 2 compartment stomach, ruminant = 4 compartment stomach) - Small intestine - Large intestine - Caecum - Rectum  GI tract = digestive tract  digestive system  Digestive system refers to the GI tract + associated organs (salivary glands, liver, pancreas, gallbladder) General Terms for Dietary CHO and Digestion  Digestibility = does the host organisms have the enzymes necessary to digest CHO? - Digestible CHO vs non-digestible CHO (fibre)  Solubility = is CHO soluble in the aqueous environment of the digestive tract? - Yes = soluble, no = insoluble  Fermentability = does the gut bacteria have the enzymes necessary to break down the CHO - Yes = fermentable, no = non-fermentable 1) Simple System w/o caecum  Monogastric stomach  Non-functional caecum  Suited for nutrient dense, low fibre diets  E.g. pig, human, cat, dog Digestion at each part of GI tract  Oral cavity: - food is chewed and mixed with saliva - 2 enzymes released: amylase and lingual lipase  Stomach (cardia, fundus, body and antrum) - Gastric emptying takes 2-6 hours (full = 1-1.5L  empty = 50 mL) - pH of stomach is acidic ~2 (important in digesting proteins) - food becomes “chyme” - gastric glands release gastric juice, gastric juice = water, electrolytes, HCL and enzymes  Small intestine: (duodenum, jejunum, ileum) - Main site of nutrient digestion and absorption - Surface area = 30m2 (this large SA enables nutrients to be absorbed) - Intestinal motility controlled by longitudinal and circular muscles - Chyme acidity is neutralized by pancreatic juice (contains bicarbonate to counter acidity) - Food digested by pancreatic juice and bile acids (bile acid solubilizes dietary fats) Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153  Large intestine (also called colon) - Site of fermentation (break down by bacteria) - Production of short chain fatty acids (SCFA) also called volatile fatty acids (VFA) - SCFA doesn’t provide much energy to the host, they are mainly used by the bacteria - Site for water absorption How is the Surface Area of the Small Intestine Achieved? 1. Kerckring folds the more folds the more sites of absorption) 2. each fold contains villi (projections) and crypts (pits) 3. each cell that makes up the villi is covered in microvilli  total SA is about the size of half a badminton court Nutrient Transport Mechanisms  passive transport (no energy input required)  diffusion and facilitated diffusion  active transport (requires energy)  they type of transport mechanism used depends on the nutrients 1. solubility 2. concentration gradient 3. molecular size Large Intestine  102 – 1012 bacteria per g content (region specific)  500 – 1000 species identified per person in the gut - different species but all have similar core function - the species of bacteria may differ in the gut of each person but there is a core preserved functionality of bacteria in everyone  1000:1 anaerobic to aerobic bacteria  bacteria is important for fermentation of non-digestible CHO - CHO fermentation produces lactate and SCFA  Gut bacteria contributes to body weight and metabolism  Foods with probiotics are trying to change and enrich the bacterial community in your gut 2) Simple System w Functional Caecum  Horse, rabbit, hamster  Hind gut fermentor  ‘pseudo-ruminant’  functional caecum  suited for a diet with large amounts of fodder (fodder – plant material)  Function of caecum - Enormous hindgut (20-30L capacity in horse) filled with bacteria allowing fermentation to take place - SCFA produced by the bacteria provide 70% of energy needs for host - Generates vitamins  A sign of energy/nutrient deficiency in horses is coprophagy where they begin to eat feces Digestion in a Horse Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153  Small intestine: sugar & starch breaks down to glucose, protein broken down to AA, fat breaks down to lipids  Large intestine: bacteria!! - fermentable fibre breaks down to volatile fatty acids, starch broken down to lactic acids, protein broken down the amino acids  indigestible fibre goes through whole GI tract with no digestion 3) Ruminant  Cattle, sheep, goats  Fermentation takes place mostly before small intestine  Large stomach divided into 4 sections 1) Rumen 2) Reticulum 3) Omasum 4) Abomasum  System highly suited for animals that eat a high quantity of fodder (hay) Ruminant Digestion  Rumen - Largest section of the stomach - Rich in bacteria (fermentation vat) - Rumen papillae  increases surface area for absorption (similar to microvilli) - Food is mixed and partially broken down and stored temporarily - 60-80% of total energy produced here through SCFA (SCFA come from bacteria fermentation)  Reticulum - Honeycomb appearance in order to capture nutrients and trap foreign materials - Rich in bacteria (fermentation vat)  Omasum - Resorption of water and some electrolytes - Filters large particles  Abomasum - Digestive enzymes secreted from gastric glands (HCL, mucin, pepsinogen, lipase, etc.) Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153 - “true stomach” similar to that of a monogastric animal  Fermentation takes place before entering the intestine (foregut digestion)  Nutrients are produced by bacteria and then become available for digestion and absorption by the ruminant  Rumination  2. Eructation (belching)  Rumen has 10-50 billion bacteria per gram of ruminal fluid  Advantages of ruminant system: - Vitamin synthesis - Non-protein nitrogen used for making protein  Disadvantages: - Carbs are degraded into gases and lost through eructation (belching) - Heat production (bacterial fermentation produced energy, and energy is heat) 4) Avian System  Birds  Beaks and claws are important for breaking up foods into smaller pieces that birds can swallow (no teeth)  Rapid digestion  Components: - esophagus  Crop (storage reservoir)  Preventriculus + gizzard (together these = the monogastric stomach) Small intestine  Cecum  Large intestine  Cloaca + vent  Crop - Enlarged area of the esophagus - Temporary storage location for food - Food is softened (often regurgitated from the crop to feed offspring)  Two chamber stomach - Glandular portion = proventriculus - Muscular portion = gizzard  Small intestine - Function is similar to other systems (nutrient digestion and absorption)  Ceca - Minor site of bacterial fermentation  Large intestine - Very short, and serves predominantly to connect the small intestine and the cloaca - Small storage of undigested material - Water absorption  Cloaca - Digestive, urinary and reproductive systems meet Digestibility  Digestibility is a measure of the fraction of a specific nutrient that is extracted by the GI tract  Calculated from the amount of nutrient in the diet and the amount appearing in the feces  Combines nutrient release from food matrix, microbial fermentation and absorption  Understanding digestibility is important in preventing deficiency and ensuring essential nutrients are available to the organism  Factors that affect digestibility: - Feed intake (food matrix) - Particle size (smaller particles move faster through GI tract decreasing their chance of being absorbed) - Chemical composition Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153 - Climate - Age (born sterile with no gut bacteria, as we age we shape our internal microbiome and become more efficient at digesting food) Total Collection Method  Animal adapts to diet (7-21day period)  Isolate animal for quantitative analysis  Measure nutrient intake over a 3-10 day period  Collect and weigh all feces over the same period  Analyze for nutrient of interest  Apparent digestibility coefficient = (total intake –total feces) / total intake  Limitations: - Not accurate - Metabolic cages (collect and analyze urine and feces) used in the experiments create anxiety which can cause animals to behave abnormally - Labour intensive - Animals confined in costly equipment - Not feasible for captive wild animals Indicator Method  Requires a marker: - Internal (natural component of the feed) - External (component added to the feed)  Characteristics of a marker: - Non-absorbable - Must not affect or be affected by the GI tract - Must mix easily with food - Easily and accurately measured in samples  Marker examples: ferric oxide, chromic oxide, silica, lignan  Steps: 1) Adapt animal to test diet (contains a marker) 2) Collect a feed and fecal sample 3) Analyze each (feed and fecal sample) for marker and nutrient of interest relative to your indicator  Apparent digestibility coefficient = (A –B) / A  Advantages of indicator method: - Less labour intensive - Ideal for wild animals Apparent vs True Digestibility  Apparent digestibility underestimates true digestibility  When apparent digestibility is calculated these things are not taken into account: - Endogenous secretions: dead epithelial cells from digestive tract appear as fatty acids in the feces - Bacterial growth in the gut: nutrient synthesis produces biotin (get bacteria produce and release vitamins) - Digestive enzymes: protein secretion (enzymes are proteins, constantly being secreted by cells and can be found in the feces) True digestibility  Preform digestibility study using a TEST DIET  Switch to diet containing none of the nutrient of interest (ZERO NUTRIENT DIET) Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153  Analyze feces after TEST DIET is cleared  Subtract level of nutrient in feces of animals fed the ZERO NUTRIENT DIET from the TEST DIET  True digestibility = (A – (B –C)) / A  A = ratio of nutrient/marker in the test diet  B = ratio of nutrient/marker in the feces  C = ratio of nutrient/marker in the feces after zero nutrient diet Energy Energy Terms  Cellular source of energy = ATP - Supplied by macronutrients in the diet, sustains physical energy, anabolism and active transport  The energy unit of food is calorie (calorie is a measure of heat)  Kcal = 1000 calories = 1 Calorie = 1 Cal  1 kcal (or 1 Cal) = 4.18 kJ  energy required to raise the temp of 1 kg of water by 1 oC Energy Balance  energy in = food and drink  energy out = metabolic and cellular function, physical activity  Positive energy balance: more energy in than out - Weight gain/obesity - Infertility - Increased blood lipids - Insulin resistance  Negative energy balance: more energy out than in - Weight loss - Infection - Loss of performance - Reduced bone mass Estimating Energy in Food  Historical methods: - Lavoisier: compared heat produced and CO2 produced by a guinea pig, ice calorimeter (heat produced estimated by the amount of ice that melts) - Liebig: recognized that proteins, carbs and fats are oxidized by the body - Rubner: measured energy values of certain foods to determine Caloric content  Calorimetry = measurement of heat production  Uses heat as an indicator of the amount of energy stored in the chemical bonds of food  Bomb calorimetry: 1. Dry and weigh sample and place in enclosed chamber with oxygen 2. Ignite sample 3. Heat released is absorbed by water and measured 4. Heat of combustion (gross energy) - Potential errors: a) Overestimate energy: we don’t digest food like a bomb calorimeter (e.g. fibre burns and releases energy but we do not digest all fibre) b) Doesn’t take into account the energy needed for digestion and absorption Physiological Fuel Values Heat of Combustion Loss in urine Apparent Physiological Fuel Value (Gross energy) Digestibility (Atwater value, available energy, metabolizable energy) (a) (b) (c) (a-b) x c Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153 Units Kcal/g Kcal/g % Kcal/g CHO 4.15 --- 97 4 Fat 9.40 -- 95 9 Protein 5.65 1.25 92 4 Why Does Fat Provide More Kcal Per Gram?  Lipid  ratio of H to O is greater than CHO  lipids have a lot of H atoms available for cleavage and oxidation for energy  CHO  ratio of H to O is 1:2  Protein  has nitrogen which contributes to gross energy in a calorimeter but our bodies dot used N for energy Fatty Acid Structure and Gross Energy  Not every fat gives the “Atwater value” of 9, 9 is just an average value  Steric acid – 18:0  9.53 kcal/g  Oleic acid – 18:1  9.48 kcal/g  Linoleic Acid – 18:2  9.42 kcal/g  Heat of combustion for fatty acids is affected by: - Chain length: the longer the chain the more energy released - Degree of unsaturation: the more double bonds the less energy released Use of Available Energy  Heat increment of feeding (HIF) - thermic effect of food - energy used for digestion, absorption, distribution and storage of nutrients - 5-30% of energy expenditure - Net energy = Available energy – HIF  Net energy: supports basal metabolism, physical activity, growth, pregnancy etc. - any energy left over after HIF is used for the processes listed above - energy goes to basal metabolic function first, then the excess after that is used for physical activity, growth etc. Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153 Partitioning Energy from Food Total Energy Expenditure  three primary components to energy expenditure: 1) basal metabolic rate (BMR) 2) thermic effect of food (same as HIF) 3) physical activity energy expenditure (PAEE)  thermoregulation can also contribute to energy expenditure but this one isn’t very important since we typically regulate temperature though clothing Basal Metabolic Rate  BMR = the minimal amount of energy you need to survive and maintain essential body processes  measuring BMR: - shortly after waking - post-absorptive state (no food) - lying down - completely relaxed - comfortable room temp  BMR = kcal/24 hours (how much energy does a person require for a day)  Muscle and bone are most reflective of BMR  BMR (basal metabolic rate) vs RMR resting metabolic rate - Essentially the same thing but RMR is a little more crude and is something you can do quicker Calculating BMR  BMR = A x [M0.75] kcal/day  A – metabolically active tissue (muscle and bone) - Constant value, humans = 70, dogs = 30, horse =155  M – body weight in kg  0.75 – Kleiber’s law – used for all vertebrates, invertebrates and unicellular organisms Harris Benedict Equation  takes into account level of activity, sex, age, weight and height Downloaded by Sophia Medeiros ([email protected])  lOMoARcPSD|30033153 Factors affecting BMR  genetics – inherits a fast or slow metabolic rate  age – young people have higher BMR than old (more muscle mass)  sex – men > women (more muscle mass)  exercise – changes body tissue proportions - putting on muscle has a significant impact on metabolic rate! - Fat tissue = 20% of body weight and 5% of metabolic activity - Muscle = 30-40% of body weight and 25% of metabolic activity - Brain, liver, heart and kidney = 5% body weight and 60% metabolic activity (this doesn’t change with exercise)  Temperature – maintaining thermoregulation can impact BMR  As age increases BMR increases  As weight increases BMR increases  And fat free mass (FFM) increases BMR increases Using % body fat to calculate BMR  If you can measure body fat % you can get a more accurate measure of BMR  Katch-Mcardle BMR equation takes into account % body fat and only measures activity of metabolically active tissue Measuring Total Energy Expenditure  All metabolic processes in the body generate heat  Heat production can be used as a measure of energy expenditure  Can be measures by direct or indirect calorimetry Calorimetry  Fuel + O2  CO2 + H20 + Heat  Indirect calorimetry measures O2 and CO2  Direct calorimetry measures heat  There is a