Obesity refers to a condition where the rabbit accumulates too much body fats due to genetic, lifestyle, diet and other risk factors. It tends to affect their normal functioning especially when they are morbidly obese due to the high-fat levels and large body size.
A rabbit is considered morbidly obese when it cannot perform essential daily functions such as walking and grooming, and it is a serious condition.
Although cats and dogs have a slightly higher prevalence, obesity in rabbits cannot be ignored. For instance, in the UK’s prevalence of 7.6% [ 1] which is probably an underestimate.
Also, the risk is higher in domesticated rabbits as compared to wild ones as the latter is always active while in the jungle being escaping from their predators as well as looking for food.
Symptoms and rabbit weight scoring
The first way to determine if this pet is obese or not is conducting a symptom physical examination. The below weight scoring system may be handy.
Note that these scorings are “scored on a scale of 1-5, where 1 is skeletal and emaciated; 5 is morbidly obese, and 2.5-3 is about right.” . A summary of Rabbit Size-O Meter courtesy pfma of is a follows:
- Score 1: Very Thin – Your pet is underweight. It will have sharp ribs, hip, and spine that can be felt, the rump will curve in, and it has no fat cover on its body.
- Score 2: Thin – Your rabbit is thin and somewhat underweight. Its characteristics are like score 1 with a little fat covering layer and a flat rump
- Score 3: Ideal – Although they can be felt, the hip bones, spine and ribs are well rounded. It has a flat rump, and the abdomen does not bulge. This is the recommended condition.
- Score 4: Overweight – You need the pressure to feel the rib, hip and spine bones. It has some fat layer, and its rump is round. Your rabbit is potentially overweight, and you need to begin helping it.
- Score 5: Obese – It is hard to feel it's hip and spine bones, and you can’t feel its ribs. Its rump belly and bulges. It has a thick fat layer.
Note that scores 1 and 2 are considered underweight rabbits while 4 and 5 are overweight and obese.
Other signs include flaky dermatitis, breathing difficulty, extreme tiredness, and grooming challenges especially on the areas under its skin folds. Also, the dewlap may be large, and it will be lazy and sluggish.
A final way is to use a rabbit weight chart. The American Rabbit Breeders Association (ARBA) has a chart that can give you the approximate ideal or expected normal weight per breed. A deviation from over 20 to 40% may indicate obesity.
The primary cause of obesity in rabbits, especially pet is poor diet and lack of exercise. There are other risk factors “associated with this problem are age, sex, neutering status, and geographical region.” 
For instance, studies have shown that high-fat diets  sucrose diet and poor diets including excessive snacks, too many carbs, proteins, and cereal mixes and excessive feeding on some commercial foods can cause weight gain. Note that some of these diets can also affect the normal functioning of a rabbit’s digestive system.
Similarly, feeding them with too much of diets based on alfalfa (has higher calories and proteins), healthy snacks including fruits such as apples, berries, melons or non-leafy vegetables such as squash, zucchinis, bell pepper and so on, excessively, can also cause obesity.
Note that these pets are folivores and their lagomorphic digestive system depends on high fiber diets especially cellulose. They may love sweet treats and enjoy eating them. However, they are not healthy.
Finally, restricting your rabbit is small cages can also be another cause as it will reduce physical activities. Ensure you have the right cage size.
It is not a good idea to assume that because your pet has too much weight, it is automatically obese and begin on strategies of managing it. Let your vet examine it as other issues including pregnancy, intestinal masses including fluid accumulation inside the gastrointestinal system may have similar symptoms.
Besides a physical examination, your vet may also conduct a few tests to determine the amount of body fat it could be having.
Risks of obesity
Possible risks and effects include the following.
- Cecal smearing as they cannot reach their anus to eat cecotropes due to the large abdomen and skin folds on their anus.
- Sore feet or pododermatitis
- Lung problems due to accumulated fats on the chest that might put pressure on the lungs thus a breathing difficulty.
- Bladder sludge 
- Urine scald
- Increases the risk of high blood pressure
- Arthritis as the excess weight might be straining its bones
- Increases risk of hepatic lipidosis
- It also affects fertility negatively with overweight bucks having a lower sperm concentration. It also affects volume, morphology, motility, and fertility . This research concludes that overfeeding can decrease sperm fertility by half.
- Some of the manifestations of this condition include “hypercholesterolemia, hyperglycemia and increased heart rate.”. Hypercholesterolemia has a detrimental effect on sperm production.
- Increases risk of heart disease due to the physical, cardiovascular, biochemical which include serum glucose and cholesterol level  and changes in the thickness of skinfold
- Dental problems if you have been feeding them on the wrong diet such as overgrown teeth if you do not give them enough hay and chew toys to wear them down.
These and other conditions associated with obesity such as GI stasis, pregnancy toxemia, ileus, myiasis (Harcourt-Brown 2002) are likely to shorten the lifespan of your rabbit.
Managing obesity in rabbits
Frightened by the possible risks of obesity, you might fall into the temptation of starving and wanting your rabbit to lose weight quickly. This is not recommended as you can push it to hepatic lipidosis where it may try to metabolize fats, something it is not good at and this can use a fatty liver or hepatic lipidosis.
Some of the best ways to manage obesity include the following:
- Proper nutrition is ensuring you stick to the rabbit’s recommended diet. Ensure it eats over 80% grassy hay (and reduce on alfalfa and other legume hay) and some leafy greens such as lettuce, kales, watercress, cucumber leaves, cilantro and so on. Do not give them fruit treats or non-leafy vegetables. Do not forget water as it is essential.
- Stop giving them processed commercial pellets such as muesli, cereal veggie blends or cereal kibbles as they can also lead to tummy problems  besides weight gain. Go for plain green pellets with high fiber content over 18% and fats below 2%.
- Ensure you gradually begin exercising your rabbits. A large rabbit run is necessary enriched with various toys and has things such as a ramp to keep it active. If you have a backyard, secure it and let your pet spend there a few hours in a day playing. For indoor ones, you can bunny-proof your house and let them reign freely.
Risk of underweight rabbit
Your rabbit being underweight or very thin should also worry you as it may indicate other problems such as dental disease (that makes them unable to eat), digestive problems including fur balls, tumor, kidney failure among other issues,
Also, starvation and not giving your rabbit enough or the right type of food can cause the underweight problem.
For long-term obesity management, work closely with your vet, stick to the right diets and continually groom your pet. Remove any fecal matter stuck on their body to avoid myiasis, clip long hairs, and continuously groom it.
- Harcourt-Brown, F. (2002). Textbook of rabbit medicine. London; Butterworth-Heinemann.