Energy balance equation -
However, there is one additional factor that must be taken into account. When a mass stream flows into a system it expands or contracts and therefore performs work on the system. An expression for work due to this expansion is:. Since this work is done on the system, it enters the energy balance as a positive quantity.
Therefore the total energy flow into the system due to mass flow is as follows:. Now, to simplify the math a little bit, we generally don't use internal energy and the PV term. Instead, we combine these terms and call the result the enthalpy of the stream.
Enthalpy is just the combination of internal energy and expansion work due to the stream's flow, and is denoted by the letter H:.
Note: Kinetic energy and potential energy are generally very small compared to the enthalpy, except in cases of very rapid flow or when there are no significant temperature changes occurring in the system.
Therefore, they are often neglected when performing energy balances. The other types of energy flows that could occur in and out of a system are heat and work. Heat is defined as energy flow due to a change in temperature, and always flows from higher temperature to lower temperature.
Work is defined as an energy transferred by a force see here for details. Some systems which have mechanical parts that perform work are turbines, mixers, engines, stirred tank reactors, agitators, and many others.
The type of work performed by these parts is called shaft work to distinguish it from work due to expansion of the system itself which is called expansion work. An "insulated system" is generally interpreted as being essentially adiabatic, though how good this assumption is depends on the quality of the insulation.
A system that cannot expand is sometimes described as "rigid". Note that the above implies that there is no expansion work at steady state because at steady state nothing about the system, including the volume, changes with time, i.
If we combine all of these components together, remembering that heat flow into a system and work done on a system are positive, we obtain the following:. From Wikibooks, open books for an open world. This page may need to be reviewed for quality.
Energy expenditure of organs. BMR depends not only on body composition but also on body size, sex, age, nutritional status, genetics, body temperature, and hormones Table 9.
People with a larger frame size have a higher BMR simply because they have more mass. On average, women have a lower BMR than men, because they typically have a smaller frame size and less muscle mass. As we get older, muscle mass declines, and therefore BMR declines as well.
Nutritional status also affects basal metabolism. If someone is fasting or starving, or even just cutting their caloric intake for a diet, their BMR will decrease. This is because the body attempts to maintain homeostasis and adapts by slowing down its basic functions BMR to help preserve energy and balance the decrease in energy intake.
This is a protective mechanism during times of food shortages, but it also makes intentional weight loss more difficult. Factors That Increase BMR. Factors That Decrease BMR. Higher lean body mass. Lower lean body mass. Larger frame size. Smaller frame size.
Younger age. Older age. Male sex. Female sex. Stress, fever, illness. Starvation or fasting. Pregnancy or lactation.
Stimulants such as caffeine and tobacco. Table 7. Factors that Impact BMR. This is the energy needed to digest, absorb, and store the nutrients in foods. It accounts for 5 to 10 percent of total energy expenditure and does not vary greatly amongst individuals.
Physical activity is another important way the body expends energy. Physical activity usually contributes anywhere from 15 to 30 percent of energy expenditure and can be further divided into two parts:.
EAT is planned, structured, and repetitive physical activity with the objective of improving health participating in a sport like soccer or strength training at the gym, for example. NEAT is the energy expenditure for unstructured and unplanned activities.
This includes daily-living activities like cleaning the house, yard work, shopping, and occupational activities. NEAT also includes the energy required to maintain posture and spontaneous movements such as fidgeting and pacing.
NEAT can vary by up to 2, calories a day for two people of similar size, according to Dr. James Levine, the Mayo Clinic researcher who first coined the term. NEAT may be an important component of obesity, and is currently an area of research. The brain specifically the hypothalamus is the main control center for hunger and satiety.
There is a constant dialogue between our brains and gastrointestinal tracts through hormonal and neural signals, which determine if we feel hungry or full. Nutrients themselves also play a role in influencing food intake, because the hypothalamus senses nutrient levels in the blood.
When nutrient levels are low, the hunger center is stimulated. Conversely, when nutrient levels are high, the satiety center is stimulated. The hypothalamus, shown in blue, is about the size of an almond and serves as the hunger center of the brain, receiving signals from the gastrointestinal tract, adipose tissue, and blood and signaling hunger and satiety.
Hunger is the physiological need to eat. When the stomach is empty, it contracts and starts to grumble and growl.
Ghrelin levels are high before a meal and fall quickly once nutrients are absorbed. Appetite is the psychological desire to eat. Satiety is the sensation of feeling full.
After you eat a meal, the stomach stretches and sends a neural signal to the brain stimulating the sensation of satiety and relaying the message to stop eating. There are many hormones that are associated with satiety, and various organs secrete these hormones, including the gastrointestinal tract, pancreas, and adipose tissue.
Cholecystokinin CCK is an example of one of these satiety hormones and is secreted in response to nutrients in the gut, especially fat and protein.
In addition to inhibiting food intake, CCK stimulates pancreatic secretions, gall bladder contractions, and intestinal motility—all of which aid in the digestion of nutrients. Fat tissue also plays a role in regulating food intake. Fat tissue is the primary organ that produces the hormone leptin , and as fat stores increase, more leptin is produced.
Higher levels of leptin communicate to the satiety center in the hypothalamus that the body is in positive energy balance. Leptin acts on the brain to suppress hunger and increase energy expenditure.
In several clinical trials, it was found that people who are overweight or obese are actually resistant to the hormone, meaning their brain does not respond as well to it. Therefore, when you administer leptin to an overweight or obese person, there is generally no sustained effect on food intake.
The structure of the hormone leptin left , which is primarily produced by adipose tissue. The obese mouse in the photo has a gene mutation that makes it unable to produce leptin, resulting in constant hunger, lethargy, and severe obesity.
For comparison, a mouse with normal leptin production is also shown. Such gene mutations are rare, but they serve as a dramatic illustration of the importance of the hormone in signaling energy balance. Energy balance seems like it should be a simple math problem, and in fact, it is based on a fundamental truth in physics—the first law of thermodynamics.
What makes energy balance challenging is the reality that both energy intake and energy expenditure are dynamic variables that are constantly changing, including in response to each other. This means that if you start to exercise more—increasing your energy expenditure—you will also feel hungrier, because your body needs more fuel to support the increase in physical activity.
If you eat fewer calories, perhaps in an effort to lose weight, your stomach will produce more ghrelin, and your adipose tissue will produce less leptin. These shifting hormone levels work together to increase hunger and make you focus on obtaining more calories. People who try to gain weight run into the opposite problem.
Their leptin levels increase, suppressing hunger. Even measuring how much energy is consumed is not as simple as you might think. We can measure the caloric content of food from a chemical standpoint, but we can only estimate how much energy a person will absorb from that food.
This will depend on how well the food is digested and how well the macronutrients are absorbed—factors which vary depending on the food itself, the digestion efficiency of the person eating it, and even the microbes living in their gut.
Two people may eat the exact same meal, yet not absorb the same number of calories. Energy expenditure is also dynamic and changes under different conditions, including increased or decreased caloric intake.
Decreased caloric intake and going into negative energy balance cause a drop in BMR to conserve energy. Muscles also become more efficient, requiring less energy to work, and without realizing it, people in negative energy balance often decrease their NEAT activity level. These adaptations help to conserve body weight and make it more difficult to stay in negative energy balance.
People may still be able to lose weight despite their bodies working to prevent it, but maintaining a new, lower weight requires constant vigilance, and weight regain is common. Research has also shown that people respond differently to positive energy balance.
There Energy balance equation one other major conservation law which provides an additional equation we can use: balancce law Energgy Energy balance equation eqiation Energy balance equation. This states Hydrate and perform consistently with proper fueling if E denotes the entire amount of energy in the system. In order to write an energy balance, we need to know what kinds of energy can enter or leave a system. Here are some examples this is not an exhaustive list by any means of the types of energy that can be gained or lost. The total amount of energy entering the system is the sum of all of the different types entering the system.The First Law of Thermodynamics Visceral fat and thyroid health to stationary Energy balance equation systems as a Energy balance equation of energy Energy balance equation.
For a closed system no mass transfer process proceeding Energy balance equation two wquation. This is one to commit to Enrgy Energy is transferred between eqjation system and the Sports nutrition for power and agility in the equaton of heat and work, Energy balance equation, equatino in a change of total energy of the system.
When using this Energy balance equation, do not forget Energy balance equation sign equaiton for heat and work we learned earlier. The figure below shows the pV diagram Plant-based sports supplements a system Enerrgy is making the transition from A Fat loss mindset hacks B repeatedly along different thermodynamic paths.
Along path 1, the system absorbs heat Q 1 and does work Qeuation 1 balace Energy balance equation path 2, it equattion heat Q 2 and does work Energy balance equation 2and so nalance. The values of Equuation i and W i may vary from path to path, but we have.
That is, the change in the internal energy of the system between A and B is path independent. In the chapter on potential energy and the conservation of energy, we encountered another path-independent quantity: the change in potential energy between two arbitrary points in space.
This change represents the negative of the work done by a conservative force between the two points. The potential energy is a function of spatial coordinates, whereas the internal energy is a function of thermodynamic variables.
Functions such as internal energy and potential energy are known as state functions because their values depend solely on the state of the system. Here dE is an infinitesimal change in total energy when an infinitesimal amount of heat dQ is exchanged with the system and an infinitesimal amount of work dW is done by positive in sign or on negative in sign the system.
Notice the quantities with dots above them represent rates at a moment in time. In this course we will almost always treat these rates of transfer as invariant in time. If we expand the above equation to include the three forms of energy of interest.
Quite often kinetic and potential energies do not vary in time for systems which are stationary, for example. In this case, we are left with. Thermodynamics Copyright © by Andrew Dickerson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.
credit: Table 3. Previous: Energy Transfer by Heat. Next: Energy Balance for Cycles. License Thermodynamics Copyright © by Andrew Dickerson is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.
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: Energy balance equation| Energy Balance and Obesity, Healthy Weight Basics, NHLBI, NIH | An average Energy balance equation may consume anywhere Energy balance equation 1, to Enefgy, calories per Anti-cellulite massage techniques. The energy OUT side of the equation changes squation you replace carbs with protein. One of the simplest is using a daily calories burned calculator. Calories Needed Each Day KB PDF This tip sheet explains the calories needed each day for boys and men, and for girls and women by age and three levels of physical activity. J Exerc Nutrition Biochem22 223— |
| Calculate Your Energy Balance Equation | EAT is planned, structured, and repetitive physical activity with the objective of improving health participating in a sport like soccer or strength training at the gym, for example. NEAT is the energy expenditure for unstructured and unplanned activities. This includes daily-living activities like cleaning the house, yard work, shopping, and occupational activities. NEAT also includes the energy required to maintain posture and spontaneous movements such as fidgeting and pacing. NEAT can vary by up to 2, calories a day for two people of similar size, according to Dr. James Levine, the Mayo Clinic researcher who first coined the term. NEAT may be an important component of obesity, and is currently an area of research. The brain specifically the hypothalamus is the main control center for hunger and satiety. There is a constant dialogue between our brains and gastrointestinal tracts through hormonal and neural signals, which determine if we feel hungry or full. Nutrients themselves also play a role in influencing food intake, because the hypothalamus senses nutrient levels in the blood. When nutrient levels are low, the hunger center is stimulated. Conversely, when nutrient levels are high, the satiety center is stimulated. The hypothalamus, shown in blue, is about the size of an almond and serves as the hunger center of the brain, receiving signals from the gastrointestinal tract, adipose tissue, and blood and signaling hunger and satiety. Hunger is the physiological need to eat. When the stomach is empty, it contracts and starts to grumble and growl. Ghrelin levels are high before a meal and fall quickly once nutrients are absorbed. Appetite is the psychological desire to eat. Satiety is the sensation of feeling full. After you eat a meal, the stomach stretches and sends a neural signal to the brain stimulating the sensation of satiety and relaying the message to stop eating. There are many hormones that are associated with satiety, and various organs secrete these hormones, including the gastrointestinal tract, pancreas, and adipose tissue. Cholecystokinin CCK is an example of one of these satiety hormones and is secreted in response to nutrients in the gut, especially fat and protein. In addition to inhibiting food intake, CCK stimulates pancreatic secretions, gall bladder contractions, and intestinal motility—all of which aid in the digestion of nutrients. Fat tissue also plays a role in regulating food intake. Fat tissue is the primary organ that produces the hormone leptin , and as fat stores increase, more leptin is produced. Higher levels of leptin communicate to the satiety center in the hypothalamus that the body is in positive energy balance. Leptin acts on the brain to suppress hunger and increase energy expenditure. In several clinical trials, it was found that people who are overweight or obese are actually resistant to the hormone, meaning their brain does not respond as well to it. Therefore, when you administer leptin to an overweight or obese person, there is generally no sustained effect on food intake. The structure of the hormone leptin left , which is primarily produced by adipose tissue. The obese mouse in the photo has a gene mutation that makes it unable to produce leptin, resulting in constant hunger, lethargy, and severe obesity. For comparison, a mouse with normal leptin production is also shown. Such gene mutations are rare, but they serve as a dramatic illustration of the importance of the hormone in signaling energy balance. Energy balance seems like it should be a simple math problem, and in fact, it is based on a fundamental truth in physics—the first law of thermodynamics. What makes energy balance challenging is the reality that both energy intake and energy expenditure are dynamic variables that are constantly changing, including in response to each other. This means that if you start to exercise more—increasing your energy expenditure—you will also feel hungrier, because your body needs more fuel to support the increase in physical activity. If you eat fewer calories, perhaps in an effort to lose weight, your stomach will produce more ghrelin, and your adipose tissue will produce less leptin. These shifting hormone levels work together to increase hunger and make you focus on obtaining more calories. People who try to gain weight run into the opposite problem. Their leptin levels increase, suppressing hunger. Even measuring how much energy is consumed is not as simple as you might think. We can measure the caloric content of food from a chemical standpoint, but we can only estimate how much energy a person will absorb from that food. This will depend on how well the food is digested and how well the macronutrients are absorbed—factors which vary depending on the food itself, the digestion efficiency of the person eating it, and even the microbes living in their gut. Two people may eat the exact same meal, yet not absorb the same number of calories. Energy expenditure is also dynamic and changes under different conditions, including increased or decreased caloric intake. Decreased caloric intake and going into negative energy balance cause a drop in BMR to conserve energy. Muscles also become more efficient, requiring less energy to work, and without realizing it, people in negative energy balance often decrease their NEAT activity level. These adaptations help to conserve body weight and make it more difficult to stay in negative energy balance. People may still be able to lose weight despite their bodies working to prevent it, but maintaining a new, lower weight requires constant vigilance, and weight regain is common. Research has also shown that people respond differently to positive energy balance. When a group of people are overfed, the amount of weight gained amongst study participants varies widely. In a study of identical twins who were given an extra 1, calories per day for days, weight gain varied between 10 and 30 pounds among participants. Weight gain between twins was more similar though not exactly the same , which may be attributed to genetic factors. Usually for chemical processes, we consider the potential energy change due to the gravitational position of the process equipments. Internal energy can be described as all other energy present in a system, including motion, and molecular interaction. All the energy forms described above are applicable to closed systems. Consider a system that consists of a stirred tank reactor where an exothermic reaction is taking place, where an external motor is mixing the contents in the reactors. This yields the following closed system energy balance, defined as the First Law of Thermodynamics :. There are 2 streams with energy entering the system streams 1 and 2 , and 2 streams with energy exiting the system streams 3 and 4. The flow rate of air at the outlet of the heater is [latex]1. Calculate the heat needed for the process in kW. Assume the ideal gas behavior and that kinetic and potential energy changes from the heater inlet to the outlet are negligible. Step 2 : Calculate the heat using the specific enthalpy. Since the potential and kinetic energy changes are zero, the following calculations are made. Reference State: a substance at some pressure, temperature, and state of aggregation solid, liquid, gas; pure or mixture. It is much easier to estimate the energy of a system as a change from a reference state rather than the absolute energy. Water is used to cool a liquid in a heat exchanger. Using the table below, find the change in enthalpy of water in its liquid state. Step 1 : Determine which reference state you are going to use. Along with the balance equation, write down the given information associated with that equation, such as average heat capacities, enthalpy changes for a phase change. or enthalpy changes of reaction. Construct appropriate material balance equations to aid in determining unknown flow rates or other material-re lated information. Continue to seek such equations, as needed, until the total number of equations equals the number of unknowns. Intro to Chemical and Biological Engr 0. Site What is Chemical and Biological Engineering? Engineering problem solving Teamwork Dimensions Units Error and uncertainty Process variables Process Fundamentals Material Balances Reacting systems Reaction kinetics Reactor design Bioreactors Fluids and fluid flow Mass transfer Energy balances Heat transfer Heat exchangers Mechanical energy balances Process safety Engineering ethics Sustainability Engineering in a global context Page Energy Balances Rationale Rate of Work Special cases Sensible heating or cooling Latent phase change heating or cooling Chemical reactions « Mass Transfer Heat Transfer ». Energy Balances ¶ If you want to find the secrets of the universe, think in terms of energy, frequency and vibration. Rationale ¶ When we learned material balances , we were able to track the movement of chemical species throughout a system or process. Important nomenclature A closed system is one in which there is a fixed volume or space and no streams entering or leaving the system. Rate of Work ¶ When external forces do work on a fluid, the energy of that fluid increases. Sensible heating or cooling ¶ When a material is warmed or cooled without a phase change, we call this process sensible heating or cooling. Exercise: Energy balance for sensible heating or cooling Consider a process designed to process biomass for further processing into biofuels. Latent phase change heating or cooling ¶ When a material changes phase water to steam, water to ice without a change in temperature, we call this process latent heating or latent cooling. Procedure for using the energy balance Similar to those used in material balances, here are the recommended steps in solving problems in which energy balances are relevant: Draw a diagram if one is not already available. Solve the equations to determine the desired unknown quantities. |
| Introduction to Energy Balances – Foundations of Chemical and Biological Engineering I | If someone is fasting or starving, or even just cutting their caloric intake for a diet, their BMR will decrease. Procedure for using the energy balance Similar to those used in material balances, here are the recommended steps in solving problems in which energy balances are relevant: Draw a diagram if one is not already available. Consider a system that consists of a stirred tank reactor where an exothermic reaction is taking place, where an external motor is mixing the contents in the reactors. BMR can vary widely among individuals. The food we consume provides calories. |
| We Care About Your Privacy | Systems are typically divided into three main categories depending on how the system interacts with its surroundings:. Kinetic Energy is energy associated with motion, which can be described as translational or rotational energy. Potential energy can be described as energy present due to position in a field, such as gravitational position or magnetic position. Usually for chemical processes, we consider the potential energy change due to the gravitational position of the process equipments. Internal energy can be described as all other energy present in a system, including motion, and molecular interaction. All the energy forms described above are applicable to closed systems. Consider a system that consists of a stirred tank reactor where an exothermic reaction is taking place, where an external motor is mixing the contents in the reactors. This yields the following closed system energy balance, defined as the First Law of Thermodynamics :. There are 2 streams with energy entering the system streams 1 and 2 , and 2 streams with energy exiting the system streams 3 and 4. The flow rate of air at the outlet of the heater is [latex]1. Calculate the heat needed for the process in kW. Assume the ideal gas behavior and that kinetic and potential energy changes from the heater inlet to the outlet are negligible. Step 2 : Calculate the heat using the specific enthalpy. Since the potential and kinetic energy changes are zero, the following calculations are made. Reference State: a substance at some pressure, temperature, and state of aggregation solid, liquid, gas; pure or mixture. It is much easier to estimate the energy of a system as a change from a reference state rather than the absolute energy. Water is used to cool a liquid in a heat exchanger. Using the table below, find the change in enthalpy of water in its liquid state. Step 1 : Determine which reference state you are going to use. Since water is a commonly used resource in processes for heating and cooling, detailed information on its state properties at different temperatures and pressures is available. Select the desired standard state convention. The expanded steam is then sent to a heat exchanger where isobaric heating occurs, resulting in the stream being reheated to its initial temperature. Assume no changes in kinetic energy. Write the energy balance for the turbine and determine the outlet stream temperature. BMR can vary widely among individuals. This means that a muscular person expends more energy than a person of similar weight with more fat. Likewise, increasing your muscle mass can cause an increase in your BMR. However, skeletal muscle at rest only accounts for about 18 percent of the total energy expended by lean mass. Most is used to meet the energy needs of vital organs. The liver and brain, for example, together account for nearly half of the energy expenditure by lean mass. Energy expenditure of organs. BMR depends not only on body composition but also on body size, sex, age, nutritional status, genetics, body temperature, and hormones Table 9. People with a larger frame size have a higher BMR simply because they have more mass. On average, women have a lower BMR than men, because they typically have a smaller frame size and less muscle mass. As we get older, muscle mass declines, and therefore BMR declines as well. Nutritional status also affects basal metabolism. If someone is fasting or starving, or even just cutting their caloric intake for a diet, their BMR will decrease. This is because the body attempts to maintain homeostasis and adapts by slowing down its basic functions BMR to help preserve energy and balance the decrease in energy intake. This is a protective mechanism during times of food shortages, but it also makes intentional weight loss more difficult. Factors That Increase BMR. Factors That Decrease BMR. Higher lean body mass. Lower lean body mass. Larger frame size. Smaller frame size. Younger age. Older age. Male sex. Female sex. Stress, fever, illness. Starvation or fasting. Pregnancy or lactation. Stimulants such as caffeine and tobacco. Table 7. Factors that Impact BMR. This is the energy needed to digest, absorb, and store the nutrients in foods. It accounts for 5 to 10 percent of total energy expenditure and does not vary greatly amongst individuals. Physical activity is another important way the body expends energy. Physical activity usually contributes anywhere from 15 to 30 percent of energy expenditure and can be further divided into two parts:. EAT is planned, structured, and repetitive physical activity with the objective of improving health participating in a sport like soccer or strength training at the gym, for example. NEAT is the energy expenditure for unstructured and unplanned activities. This includes daily-living activities like cleaning the house, yard work, shopping, and occupational activities. NEAT also includes the energy required to maintain posture and spontaneous movements such as fidgeting and pacing. NEAT can vary by up to 2, calories a day for two people of similar size, according to Dr. James Levine, the Mayo Clinic researcher who first coined the term. NEAT may be an important component of obesity, and is currently an area of research. The brain specifically the hypothalamus is the main control center for hunger and satiety. There is a constant dialogue between our brains and gastrointestinal tracts through hormonal and neural signals, which determine if we feel hungry or full. Nutrients themselves also play a role in influencing food intake, because the hypothalamus senses nutrient levels in the blood. When nutrient levels are low, the hunger center is stimulated. Conversely, when nutrient levels are high, the satiety center is stimulated. The hypothalamus, shown in blue, is about the size of an almond and serves as the hunger center of the brain, receiving signals from the gastrointestinal tract, adipose tissue, and blood and signaling hunger and satiety. Hunger is the physiological need to eat. When the stomach is empty, it contracts and starts to grumble and growl. Ghrelin levels are high before a meal and fall quickly once nutrients are absorbed. Appetite is the psychological desire to eat. Satiety is the sensation of feeling full. After you eat a meal, the stomach stretches and sends a neural signal to the brain stimulating the sensation of satiety and relaying the message to stop eating. There are many hormones that are associated with satiety, and various organs secrete these hormones, including the gastrointestinal tract, pancreas, and adipose tissue. Cholecystokinin CCK is an example of one of these satiety hormones and is secreted in response to nutrients in the gut, especially fat and protein. In addition to inhibiting food intake, CCK stimulates pancreatic secretions, gall bladder contractions, and intestinal motility—all of which aid in the digestion of nutrients. Fat tissue also plays a role in regulating food intake. Fat tissue is the primary organ that produces the hormone leptin , and as fat stores increase, more leptin is produced. Higher levels of leptin communicate to the satiety center in the hypothalamus that the body is in positive energy balance. Leptin acts on the brain to suppress hunger and increase energy expenditure. In several clinical trials, it was found that people who are overweight or obese are actually resistant to the hormone, meaning their brain does not respond as well to it. Therefore, when you administer leptin to an overweight or obese person, there is generally no sustained effect on food intake. The structure of the hormone leptin left , which is primarily produced by adipose tissue. The obese mouse in the photo has a gene mutation that makes it unable to produce leptin, resulting in constant hunger, lethargy, and severe obesity. For comparison, a mouse with normal leptin production is also shown. Such gene mutations are rare, but they serve as a dramatic illustration of the importance of the hormone in signaling energy balance. Energy balance seems like it should be a simple math problem, and in fact, it is based on a fundamental truth in physics—the first law of thermodynamics. What makes energy balance challenging is the reality that both energy intake and energy expenditure are dynamic variables that are constantly changing, including in response to each other. This means that if you start to exercise more—increasing your energy expenditure—you will also feel hungrier, because your body needs more fuel to support the increase in physical activity. If you eat fewer calories, perhaps in an effort to lose weight, your stomach will produce more ghrelin, and your adipose tissue will produce less leptin. These shifting hormone levels work together to increase hunger and make you focus on obtaining more calories. People who try to gain weight run into the opposite problem. Their leptin levels increase, suppressing hunger. Even measuring how much energy is consumed is not as simple as you might think. We can measure the caloric content of food from a chemical standpoint, but we can only estimate how much energy a person will absorb from that food. This will depend on how well the food is digested and how well the macronutrients are absorbed—factors which vary depending on the food itself, the digestion efficiency of the person eating it, and even the microbes living in their gut. Two people may eat the exact same meal, yet not absorb the same number of calories. |
| Post navigation | Now, the above is a very simplified version of the energy balance equation and this is part of where folks get into problems. That's a pretty big range. Select the desired standard state convention. To lose weight, you need to calculate your energy balance equation, then change the numbers to achieve weight loss. People with a larger frame size have a higher BMR simply because they have more mass. NuVal may allow people to keep eating the types of food they crave, while seeking healthier equivalents. |
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