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How Food Supplements Affect Weight Gain of Juvenile Mice

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As your mom and dad always tell you, a healthy diet is important to good health. This project is designed to see what happens to mice when they are allowed to load up on sugary snacks. Do you think that they will gain excess weight? Do you think that the mice will regulate their own intake and maintain a 'healthy' diet? You can try this project and find out for yourself.


Areas of Science
Time Required
Average (6-10 days)
For experiments involving vertebrate animals, ISEF-affiliated fairs require the experimental design to be approved by a scientific review committee (SRC) prior to the commencement of experiments.
Material Availability
Readily available
Low ($20 - $50)
No issues
Andrew Olson, Ph.D., Science Buddies
Sources The original idea for this project is from:

Information on marking mice is from:

Information on handling mice is from:


The goal of this project is to determine whether feeding juvenile mice supplements of different food types would lead to increased weight gain.


When speaking about proper nutrition, we often use the word 'balance.' You often hear, for example, how important it is to eat a balanced diet. Health-conscious people also strive to maintain a balance between calories consumed and calories expended, by getting regular exercise and eating regular, healthy meals.

What happens when the diet is imbalanced? Can consumption of too many simple carbohydrates lead to weight gain? How about other types of food? These kinds of questions can be difficult to answer with studies on humans, since it would be unethical to knowingly subject experimental subjects to unhealthy diets. As an alternative, scientists can conduct epidemiological studies, looking at health outcomes for groups of people with different dietary habits. Another method is to use animal models for more carefully controlled experimental studies.

Mice are often used as experimental animals for many reasons. One of the biggest reasons is the degree of control that scientists have over the genetic backgrounds of the mice they study. Specific genes of interest can be turned off or on, or regulated more subtly. Also, since mice grow quickly, it is easy to generate sufficient numbers of mice with similar genetic backgrounds.

Small, warm-blooded animals, such as mice, generally have much higher metabolic rates (and shorter lifespans) than larger warm-blooded animals. Typical laboratory mice live about one and a half years. Mice are considered infants from birth to 21 days of age. At 21 days they are weaned—they stop nursing and switch to eating solid food. Mice are considered juvenile from 3–8 weeks. At 2 months, mice are considered adults, and are capable of producing offspring (NIDDKD, 2005b).

Even though mice have many genetic and biochemical similarities with humans, experimental outcomes with mice are certainly not guaranteed to be similar to experimental outcomes with humans. Still, experiments with animal models can provide us with many valuable insights to help fight human diseases.

Terms and Concepts

To do this project, you should do research that enables you to understand the following terms and concepts: Questions


Materials and Equipment

To do this experiment you will need the following materials and equipment:

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Experimental Procedure

Note: for experiments involving vertebrate animals, ISEF-affiliated fairs require the experimental design to be approved by a scientific review committee (SRC) prior to the commencement of experiments. Please refer to the ISEF rules for additional important requirements for studies involving vertebrate animals: http://www.sciencebuddies.org/science-fair-projects/project_src_safety_human_subjects.shtml.
  1. Place six mice in each cage. Both groups will have free access to standard laboratory mouse food and water.
  2. Feed the mice in cage 1 a supplemental food high in simple carbohydrates (e.g., sugared breakfast cereal) two or three times a day.
  3. Mice in cage 2 (the control group) will receive no supplement.
  4. Record the weight of each mouse daily. How do you tell them apart? Here are some tips for marking mice from the mouse experts at The Jackson Laboratory:
    1. "Several methods are particularly well suited for identifying cage mates. A felt tip marker may be used for marking an ear or tail: such marks usually disappear in 1-2 days.
    2. "Food coloring may be used to dye a patch of fur: such marks generally last for 1-2 weeks but can be used only on albino and light colored mice.
    3. "A patch of fur on the back or side of the mouse may be shaved: such marks generally last 1-4 weeks (depending on stage of the hair cycle) and can be used on any color mouse." (Jackson Laboratory, 2005)
  5. For handling the mice in order to weigh them, there are three different methods you can try. Whichever method you choose, transfer the mouse to the weighing container smoothly and quickly.
    1. If you can manage the hand scoop method, it is probably the least stressful for the mice. However, you do need to be careful not to let the mouse escape.
      Close up image of a mouse standing on a human hand

      Figure 2. The hand scoop method is usually the least stressful way of handling mice.

    2. The tail hold with hand support is the next method. Grasp the tail of the mouse close to the body (no further than half-way down the tail). Support the mouse's feet with your other hand.
      A mouse stands on the back of a hand while another hand pinches the mouse's tail

      Figure 3. The tail hold with hand support is an alternative method for handling mice.

    3. The tail hold alone is the final method. Remember to always grasp the tail of the mouse close to its body. Lifting near the tip of the tail will injure the mouse. Do not leave the mouse hanging, or it will climb its tail and try to bite.
      Two mice are lifted into the air by their tails

      Figure 3. The tail hold alone is the third method for handling mice.

  6. Calculate the weight gain for each individual mouse.
  7. Calculate the average and standard deviation of the weight gain for each group of mice.
  8. More advanced students should use Student's t-test to determine whether any differences between the two averages are statistically significant. The Bibliography has a link to an online calculator you can use (Kirkman, date unknown).
icon scientific method

Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.


  • If you want to collect data on caloric intake, you can also weigh the food each day to figure out how much the mice have eaten.
  • In this experiment, the food supplements primarily contained simple carbohydrates. What about other nutrients? Design an experiment to test weight gain when the food supplement contains a high proportion of fat, or protein.
  • When it comes to gaining or losing weight, diet is only part of the equation. Diet determines the number of calories on the input side, but an animal's activity determines how many of those calories are used. Design an experiment to assess the difference in weight gain between "couch potatoes" and active mice.
  • What role does genetics play in weight gain? Test different strains of mice for weight gain. Keep diet and exercise the same for both groups.


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MLA Style

Science Buddies Staff. "How Food Supplements Affect Weight Gain of Juvenile Mice." Science Buddies, 20 Nov. 2020, https://www.sciencebuddies.org/science-fair-projects/project-ideas/MamBio_p007/mammalian-biology/how-food-supplements-affect-weight-gain-of-juvenile-mice. Accessed 7 June 2023.

APA Style

Science Buddies Staff. (2020, November 20). How Food Supplements Affect Weight Gain of Juvenile Mice. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/MamBio_p007/mammalian-biology/how-food-supplements-affect-weight-gain-of-juvenile-mice

Last edit date: 2020-11-20
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