Energy Balance: How the Body Uses Energy

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  • 0:02 Energy Balance
  • 1:21 Basal Metabolism
  • 4:18 Physical Activity & NEAT
  • 5:15 Thermic Effect of Food
  • 5:55 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Energy balance is the relationship between the energy you take in and the energy you use. Learn how you take in energy from the foods you eat and how your body uses that energy for your basal metabolism, physical activity and food digestion.

Energy Balance

Your body is a highly efficient machine that's at work 24/7 taking the energy, or calories, you provide from the foods you eat and turning it into energy that can be used by your body to keep you going strong. Energy balance is the relationship between the energy you take in and the energy you put out. So, when you consume the same amount of energy as you use, your energy is balanced, and your body weight stays the same.

Unfortunately, judging by the rapidly growing obesity epidemic in the U.S. and other countries, it seems that many people are in an energy imbalance, where they are taking in more calorie-yielding nutrients, namely fats, carbohydrates and proteins, than they are expending. The reasons for the higher energy intake are easy to see.

In America today, foods are easily obtained at all hours via grocery stores and convenience stores that stay open 24 hours. Every few miles there's a fast food restaurant waiting to provide us with a calorie-dense meal delivered right through our car window. Yet if we only look at how the body takes in energy, we're only looking at half of the energy balance equation. So, in this lesson, we will consider the different ways your body uses the energy you feed it.

Basal Metabolism

Most of the total energy your body uses each day goes to what we call basal metabolism, which is the minimum amount of energy needed to maintain your bodily functions while at rest. This includes how much energy your body burns to keep you breathing, keep your blood circulating and maintain the many vital cellular activities that keep you alive. It might help you to recall this term if you think of 'basal' as basic and 'metabolism' as energy use. So basal metabolism is your basic energy use, which is kind of like a program that's minimized on your computer - the basic program is still running and using energy, but not actively.

The rate at which energy is used for these vital functions is called the basal metabolic rate (BMR). This does not include energy used for physical activity or to digest your food, but we will consider these issues in a bit. BMR varies from person to person, so let's look at some factors that influence BMR. One thing that makes a difference is a person's size. Larger people tend to have a higher BMR because their increased surface area releases more heat, which increases the basal metabolic rate.

Body composition, which is the proportion of fat versus fat-free mass, also affects BMR. This is because lean muscle is more active than fat and therefore, requires more energy. So, the more lean muscle mass you have, the higher your basal metabolic rate. This also explains why gender is a factor that influences BMR, as men tend to carry more lean body mass than women and therefore, tend to have a higher BMR. This is also why age is a factor, as we tend to see BMR decrease with age, which may be due to an expected drop in lean body mass that occurs as we age.

Did you ever hear someone complain that they feel sluggish due to an underactive thyroid? Well, they might be telling the truth. Technically, an underactive thyroid gland is termed 'hypothyroidism,' and it means that your thyroid gland is not producing enough hormones. One hormone that we see drop is thyroxine (T4), which is a hormone released from your thyroid gland that affects your metabolic rate. Therefore, we can say that hormonal levels qualify as a factor that influences your BMR.

Now, before we move one, let's give you one more factor, and that is calorie intake. If you ever went on a strict diet, you might have firsthand knowledge of how this affects your metabolism. Basically, if you lower your calorie intake, you lower your BMR. This is a frustrating fact if your goal is to lower your calorie intake in order to lose weight, because as you eat less, your ability to burn calories goes down.

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