Effects of Feasting & Fasting on Cells

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Substrate-level Phosphorylation and Oxidative Phosphorylation

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:01 Feeding Your Cells
  • 0:56 Feasting
  • 3:17 Fasting
  • 5:04 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed

Recommended Lessons and Courses for You

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.

Your cells use the nutrients from the foods you eat to fuel vital functions. If you eat too much (feast), excessive nutrients get pushed into storage. If you eat too little or not at all (fast), stored nutrients can be pulled out of storage and used to meet your body's needs.

Feeding Your Cells

Did you know that when you eat, you're actually feeding your cells? I say this because it's the cells in your body that take the nutrients from the foods you eat and use them to carry out the vital functions that keep you running. In a way, you could say that food does the same thing for your body as gasoline does for your car. Of course, your body's a bit more complex than your car.

You see, your body has the ability to store nutrients in places, like fat, the liver and muscles, when you overfeed it, and then draw on these nutrients at a later date if you're running low on fuel. Your car can't do this - try to give your car more gas than the tank will hold, and you will have a mess on your hands. In this lesson, we will take a look at how your cells handle the extra food that comes in during a period of feasting, as well as what happens when you fast.


When I think of feasting, I get an image of a big Thanksgiving meal. When you look at the table on Thanksgiving Day your eyes see turkey, stuffing, buttered rolls and pumpkin pie, but when you get the food inside of you, your digestive tract sees macronutrients, namely carbohydrates, proteins and fats. Your digestive tract breaks these nutrients down into their basic forms so they're small enough to absorb into your bloodstream, which is the highway that nutrients use to reach your blood cells.

One of the first priorities for your body is energy production, and we see that glucose, which is a simple carbohydrate, is a quick and easy energy source. Glucose that is not needed for immediate energy is sent to your muscle and liver cells for storage as glycogen, which is an easily accessible form of stored glucose. This is nice to have, but there's not a lot of room in your muscles and liver to store glycogen, so the excessive carbohydrates that you eat will get converted into fat and stored in adipose tissue, the soft substance that you think of as body fat.

Body fat is not as easy to convert back into energy as glucose or glycogen, but it is an efficient way to store energy for the long-term. So, when it comes to the way your body handles carbohydrates you might want to think of glucose as gas that's in your tank ready to be used; glycogen as a few small, easily-accessible gas cans that you have stored in your garage; and fat as the gas stored at the gas station that you can access when you really need it.

Now, as you might suspect, excessive fats from your Thanksgiving feast are also stored in adipose tissue. This adds to your stored energy reserve, which is a nice way to say you gain body fat. As for the proteins from your meal, well, they get broken down into their basic building blocks called amino acids by your digestive tract, and are then reassembled as new proteins within your cells. Excessive amino acids that are not needed to make proteins don't really have a storage space in your body. Therefore, the extra amino acids tend to be broken down for energy. If this energy goes unused, it can be converted to fat.


Now, let's say that after you stuff yourself on Thanksgiving Day, you decide to stop eating for a while. During the fast, the major players that we discussed earlier, namely your adipose tissue, muscles and liver, work somewhat in reverse to make sure your body has the energy it needs to keep functioning. For example, at the start of your fast your liver cells break down glycogen molecules into glucose, and your fat cells break down fats into fatty acids. Your body can burn these fatty acids for additional energy.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account