Overweight rabbits are prone to a lot of additional diseases and problems, as we have mentioned. Diabetes, arthritis, liver issues, pancreatic problems, heart ailments...but some of the most visible issues, the ones you are most likely to notice first, start at the end. The end of the rabbit. The bum.
Overweight rabbits can't get back to their private bits to clean properly, so your friend can end up with poopy bum. The fur becomes matted and gunky, smelly, and really rather disgusting. Urine gets soaked up or trapped by this mess as well, so the rabbit will often end up with urine scald - irritated skin caused by the urine staying in contact with the skin. Urine scald can be painful, and the skin can become infected. In the worst cases, there can be open sores.
This mess also gets in the way of the caecotrophs that your rabbit needs so much. A rabbit whose caecotrophs become part of the matted mess are missing out on critical nutrition. These little clusters of goodness are absolutely vital to your rabbit staying healthy, so if they are lost in the mess, or contaminated with old urine and therefor rejected, we've got an even bigger problem on our hands.
We'll be talking about how to clean up bunny bums in the near future, but for now, just know that you CAN soak your rabbit's bum in a nice lukewarm stream of water, and use your fingers to gently loosen the goo. Make sure your rabbit feels secure and is in a safe hold before you try this. If your rabbit is upset by a bum bath, you can use a large bowl instead of the sink. Just lower your rabbit into the bowl gently, and make sure that if your rabbit jumps out he won't jump off a table! Towel dry very gently as much as possible (remember, there can be some sensitive skin under there), then air dry, and then take a good look at the situation. If there is any pink skin, any signs of urine scald, get some help from your veterinarian. It may help to clipper the area, and there are creams and antibiotics to prevent or get rid of any infection. Your bunnies' behind is going to need some careful monitoring.
Please DON'T give your entire rabbit a bath! For most rabbits this would be very traumatic, and also causes fur to matt like felted wool...again, now we have a bigger problem.
Your friend will be so much more comfortable without that mess, and will have better nutrition too. Nobody loves to clean up a poopy bum, but you'll be doing your friend a HUGE favor.
Here's to nice bums! And...up next: some super important info on why it is important to lose that weight slowly.