Ferrets have two things going for them: They are naturally very active, and they only eat until their caloric requirements are met (they seldom overeat). This combination of traits makes a fat ferret an extremely rare condition.

You will note, though, that as winter approaches, your ferret will tend to gain weight - as much as 40 percent. However, don't confuse this with obesity, because he will lose these extra pounds again in the spring. Here's what you can do to determine if your ferret is obese:

  1. Run your hands along the sides of your ferret's body. His body should feel muscular to the touch. If he feels soft or mushy, then he might be overweight.
  2. Look at his ribcage area. If your ferret is within the correct weight range, you should be able to see the ribs under his skin, but they should not be prominent.
  3. Take him to the veterinarian for a checkup. Even if your ferret is overweight, it might not be because of excess fat. Other major causes that can make your ferret too heavy include large tumors, an enlarged spleen (which is fairly common, resulting from tumors or cardiomyopathy) or congestive heart disease (which causes large amounts of fluid accumulation, especially in the abdomen). A visit to the veterinarian will determine if your ferret is indeed suffering from illnesses that make him overweight.
Obesity in ferrets has similar effects to obesity in humans: shortened life span, reduced physical activity and health complications, including congestive heart failure. And as with humans, it's easier for ferrets to add body fat than to remove it. So if your ferret is obviously defying his natural predisposition by putting on excess fat, you need to remedy the situation to ensure his good health.

Your veterinarian can help you:

  • Put your ferret on a leaner diet by mixing his normal food with a lower-calorie food (less protein and fat). You can also switch completely to a restricted-calorie ferret food.
  • Reduce or eliminate treats and commercial supplements, especially sugary ones, from your ferret's diet.
  • Increase your ferret's exercise time and regimen by letting him out of his cage more often and encouraging him to run and play more.
  • Give your ferret more toys to make his activities more interesting. Bored ferrets eat and sleep more, and thus tend to gain unwanted weight.