What does metabolizable energy really mean? In order to understand that we have to have some feel for what metabolism is, Metabolism: the energy consumption by biochemical process. Everything that goes on in our body takes some effort. where does this energy come from? Food! As suggested before, we are like an engine and food is our fuel. The basal metabolic rate (BMR) is the amount of energy that we would expend over a 24-hour period by doing nothing. Your body is expending energy just by working its inner functions. Technically, you can’t “burn a calorie”. A calorie is just a measure of energy. What we really mean to say is that we ’r e going to need energy and were going to be burning some food components in our body to produce that amount of energy. We equate the calorie content to a certain amount of food. But literally speaking, it isn’t correct to say you’re burning calories. Instead yo u can say you’re burning food c omponents with the release of calories.
CHEM 181 Winter 2019 Malka A-r 194 We can measure that, for example, by looking at walking. If you’re walking at about five to six kilometers per hour, you’re burning about four calories per minute. How do we know this? There’s several ways to det ermine it. 1. You can put people in a room that is thermally insulated from the outside, have them do some kind of activity, and measure the temperature change in that room. The temperature change comes from the energy that is being expended for doing that activity. 2. You can measure the amount of oxygen that is inhaled and the amount that is exhaled of carbon dioxide, because that is proportional to the “burning of calories”. Any combustion process requires the combination of the food component with oxygen to release carbon dioxide and water. So, we can measure the intake of oxygen and the exhaled amount of carbon dioxide. Other activities • Dancing: …………………………… 5.5 calories a minute. • Bicycling 21km/h : ……………... 8 calories a minute. • Swimming :………………………. 11 calories a minute • Running 16km/h : ……………… 16.5 calories a minute Burning calories with exercise is definitely not easy. Want a piece of apple pie with ice cream on top? Dat shit is 500 calories. To compensate for that, you’d have to do 1 hour of bicycling ! The basal metabolic rate (BMR) varies depending on body size and sex. Its about 1500- 1700 calories per day Video 4 As we have already discussed, the basal metabolic rate is the amount of energy that your body expends just to stay alive, to make the brain, heart lungs etc. function. It varies; it is less in women than in men since women are generally smaller in body size. There are many other variables in determining he basal metabolic rate. For example, imagine there are two cars. They have equal gas tanks, but they are two different kinds of cars. We fill the gas tank with gasoline. So the amount of potential energy is the exact same since we ’ ve put the same amount of gasoline into the two cars. Then you put a driver into each car and say drive. Now ask yourself; when will the car run out of gas? Well, the total amount of energy that is available is the same in both cars. But… that doesn’t mean they’ll run
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