When Rats Need to Diet

imageOh Dear!

Is your sweet rat shaped like a PEAR, instead of a proper SAUSAGE?

Identifying your rat as a pear or a sausage is not all there is to deciding whether to diet a rat. Consider the overall health of the rat, the history of previous diets, any previous weight changes over time, genetic factors, age, and other stressors present. An example of a stressor that would mean you should not start a diet (yet) is if the rat just came from a bad environment and hasn't settled down.

What do you need to properly diet a rat? These are critical:

1. Obtain a thorough assessment of your rat's health by a vet.

2. You must have a gram scale. No scale? Don't try to diet your rat. It will be too difficult due to the very fine calculations you need to make over time. These calculations are to insure that you don't withhold too much food as weight loss progresses.

3. Plan to weigh the rat and the food portion every week.

4. Set up a log book where you will write down the weights of food and rat every week. 

5. Celebrate the results of a good diet!  Your rat will appreciate you!


NOTE: I no longer have the excel file that I describe at the bottom of this page. (An image of it is at the bottom.) Because of this, I'm giving the formula here so that you can do the manual calculations. 

General conditions to follow, as reviewed and approved by a veterinarian:

1. Weigh the rat at the start. Weigh what you think is the normal total food you have been feeding each day. (Write these down.)

3. You must weigh the rat weekly for these calculations to work.  Not on day 4, or on day 15.

4. Plan to feed exactly the same foods every day.  So if you hand out a blueberry every day, stay with one blueberry. See how the following example is a problem: Feeding 30 grams of a pellet one day, and then 15 grams of a pellet and 15 grams of a butter cookie the next day.  Even though each day stays with 30 grams total weight, higher calories for any days will distort the diet. Aim to keep to the same number of calories each day.

5. Remove any food that has been stashed in the cage. If the rat stashes any food, remove that stash. No stashing allowed because we want to make sure the diet is following the rules! To eliminate stashing, feed very small pieces. Chop up pellets to 1/4 inch pieces.  You want to see rats eat tiny pieces right there and then without moving to a hidden spot.  One reason stashing larger pieces occurs is because it's not safe for a rat sit in the open for a long time to eat a big pellet.  A hawk might swoop in! Another reason a rat stashes is if she has eaten to the point of feeling full, so she'll save some for later. If this happens, stop feeding, and remove the stash.

6. If at any time during a diet your rat becomes ill, or perhaps gets spayed or neutered, stop the diet until the rat returns to a baseline healthy state.

Here in a nutshell is the formula for a safe diet:

Calculate 1% of the rat's daily total food, and subtract that amount from that total. Then feed the new weight of food next week. Look for a maximum 1% weight loss per week for the rat.  Repeat weekly until your rat become a sausage and not a pear.

Here's how to work this diet over time: 

1. Weigh your rat at the start. (Write this down.)

2. Weigh the total food you've been giving per day. (Write this down.)

3. Multiply the total weekly food portion by 1%.  

4. Subtract that 1% amount from the total you've been feeding (write this down), and then feed only that new amount for the first week of the diet.

5. Week two, weigh the rat.  Write this down! :)

6. Calculate if the rat has lost 1% of her original weight. To do this, multiply last week's weight by 1%, and subtract that amount from that weight. The amount you get is the weight  you hope to see at the end of the first week.

7. Repeat the above every week. Over time you will slowly reduce the food, and slowly reduce the rat's weight.  This method is the least stressful on the rat, where keeping stress low is really important.

8. You may see the rat's weight go up or down over any few weeks. This can be normal. If the rat has gained weight from the previous week, or lost more than 1% from the previous week, don't change what you've been feeding. Stay with the same food portion over 2-4 weeks and look for an average 1% loss per week.  If you still have a problem, increase or decrease the food you're giving by a tiny amount. This should help you get back to the best average 1% loss per week. Adjusting food portions is part of the game here!

Jump for joy as you see your rat's weight improving! She will thank you!


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Are you considering putting your rat on a diet?

Under the photographs below is a full-length image of my Excel workbook from 2008, (no longer available to share).  It shows how the diet looks from week to week. 

Below are also are pictures of Bright Biggity Buxom Bonny Bon-Bon at various weights. She was my inspiration for enforcing weight loss. Bonny was distinctly obese at 9 weeks of age, and remained so throughout her life. At one point her fattiness got too extreme, and dieting helped me help her back to a more manageable (though still over) weight.

Sample of my Excel spreadsheet for tracking a rat's diet. (First effort on my part to diet rats and to track their weight loss.)
I enter:

1. The starting weights of the rats, and the date I weigh them.

2. A guess about their ideal weight (I can change this any time.)

3. Then, next time I weigh them, I enter the date (light green cell), and their weights (light yellow cells).

4. The critical info to zero in on is, "% change (-/+)". What I want to see here is as close to 1% as possible. In the date of 4/1/08, for the first rat, Bonny, I see -2.81%. This told me she lost WAY more than 1%. So I adjusted the amount of food she got for the next week, UP, to stabilize her weight loss.
But as you can see in the following weeks, she continued to loose too much weight.  It took me a long time to nail down the right portions (weight of food/per week) before she stabilized and eventually reached a good weight.)

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