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Body Composition

Young people will learn about what the body is made of and the role of each body component.


3-14 Years Old


45 Minutes

What You Need


Healthy Families Newsletter

English (pdf)

Spanish (pdf)

To find out how this health safety lesson fits Physical Education and Health Education standards click here.

Lesson Overview

Bodies get a lot of attention in our society, some of it not very positive, much of it focused on appearance more than actual health. This lesson helps young people understand different components that make up the structure of the human body. Youth will learn how eating and exercise habits influence how much muscle and fat each person has inside their body.

Instructor Notes

Before facilitating this lesson, you may want to review the following information about body composition. These facts can also be shared with young people during your discussions.

  • Body weight is the combination of muscle, fat, organs, fluid, tendons, ligaments, and bones.
  • The human body is made up of about 600 to 700 muscles.
  • Voluntary muscles attached to the skeleton allow the body to move, while involuntary muscles allow the movement of internal organs.
  • Voluntary muscles are the muscles that you can move by thinking about it. You can flex your bicep muscle by lifting up your arm and “showing how strong you are.” They are called voluntary because you can make the decision to do it, just like you can volunteer to wash dishes after dinner. Involuntary muscles are those muscles that work automatically; you do not have to think about digesting your food, or flexing your own heart to pump blood around your body.
  • Ligaments are tissues connecting bones to other bones to form joints.
  • Tendons connect muscle to bone.
  • Bone is hardened connective tissue that supports the body, protects organs, and aids movement of the body. Bones store minerals, these minerals are phosphorus, magnesium, fluoride and calcium, and are involved in cell formation. The body is made up of 206 bones.
  • The heart is an organ. It is also a muscle that pumps blood through the body.
  • The lungs are organs that exchange oxygen from the air with carbon dioxide from the blood.
  • Fat is unused energy.
  • The intestines absorb nutrition from food to be used by the body. They allow the nutrients to enter the blood.
  • The stomach releases enzymes that break down food into nutrients that can be used by the body.


Show the youth the two containers (don’t show the inside). One box is filled with a heavy item the other a lighter item.

Ask: Can you tell what is inside? Both boxes are full.

Let the young people handle the boxes, feeling the differences in weight.

Ask: Do you think both boxes have the same materials inside? Why?

Explain that you can’t tell what is inside the packages by looking at the outside. Our body is just like these packages. We see the outside, but do not know what is inside. Each body is different. All of our bodies have: muscle, fat, organs, fluid, tendons, ligaments, and bones. All these combined make up our total weight.

Activity: Body Components

Looking at how the body is put together will help young people understand that everybody is different. Each person has a unique body and unique needs. Introduce 5 components of the human body.

If you have access to a projector and the proper software, use the the interactive whiteboard files to guide young people through learning about the parts of the body. In unavailable, discuss the following facts with the youth.

  • Your body is made up of five separate components, each of which has an important role:
    • Bones give you height and support your body. How many bones do you have in your body?  206
    • Muscles give you movement and strength. How many muscles do you have in your body? 600 to 700
    • Internal organs support life. Can you name some of your organs? Skin, stomach, intestines, liver, spleen, pancreas, heart, brain, lungs, gall bladder, kidneys, and bladder.
    • Skin keeps you together and your organs inside your body.
    • Fat keeps you warm, protected, and provides stored energy.
  • All of these components change with age and level of activity.
  • Two people could look alike on the outside and weigh the same, but be very different on the inside. Our eating and exercise habits, along with age and genetics, determine how much muscle and fat each person has inside their body. Eating healthy and being active helps our bodies in the following ways:
    • strengthens our muscles
    • keeps our heart, lungs, and bones strong
    • helps build the right amount of protection and stored energy
    • and helps our organs work properly.

If we eat unhealthily and are not active, our muscles and bones become weak, our heart and lungs have to work harder to do their jobs, and sometimes we store extra fat our bodies do not need.

Ask: What happens to your body when you get older (grow taller, gain weight, muscles become stronger)? What are some activities we can do to keep our bodies healthy as we get older? What are some foods we should eat to keep our bodies healthy as we get older? What kinds of food and activities could make you unhealthy and be bad for your body?


Point out that our human beings are amazing and complex! Encourage young people to try to make choices every day that help their bodies be healthy, strong and fit.

Continuing the Conversation

Hand out the Healthy Families Newsletter in English or Spanish so that families can continue discussing body composition at home.

Additional Instructor Resources

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