As I have mentioned previously, it's a fantastic idea to get into the habbit of checking your pets health weekly and this should include weight and body condition.
Always keep an eye out for any changes and logging this weekly will help you spot anything quickly.
The Rabbit Size-O-Meter by the PFMA is a really great tool to measure body weight and I have attached it here.
If you aren't sure you can always ask the opinion of your rabbit savvy vet- especially if you worry something has changed. You will need to get close to your bun to physically feel them to make the assessments- in some breeds the coat can hide thier actual body shape!
Weighing them weekly is also a good idea and there are two ways you can do this- firstly you could buy special baby scales from somewhere like Amazon or you could simply weigh them on your normal bathroom scales in a carrier (but remember to remove the weight of the carrier!)
Over time your pet will get used to this and being so hands on could be a great way to bond.
..me and Snoop.... make the weekly health check fun and great time to bond!
If your bunny does need to lose a bit of weight I would always double check with your vet but ensure the majority of the diet is good quality hay- it could be the rabbit is eating too many treats at the expense of the hay! Before you go you could keep a food diary and this could help your rabbit find a suitable diet plan.
If a rabbit needs to increase his weight the best way to do this is still to feed a balanced diet as they need to gain muscle and not just fat- so again ask your vet rather than just opting for high calorie foods. Things like Supreme Fibafirst sticks are a great addition to the diet as you can generally give up to 5 a day and they are very high in crude fibre too. Biut do always check with a rabbit savvy vet!
It is better for a rabbit to be slightly underweight as oposed to overweight as overweight rabbits are more at risk of certain problems. For example overweight rabbits are not able to clean themselves or reach their bottom to eat their caecotrophs – which puts them at greater risk of skin infections and flystrike. (RWAF)
..my bunny Snoop began to put on weight ... I wonder why!!! Luckily it was spotted quickly and he is back to a healthy weight!
Remember all breeds are different and if you're starting out and not sure what the ideal weight is for your bun get your vet to weigh them first (most will do this at the same time as something else like a nail trim) and then you can use that as a starting point to monitor at home.
Hope you have found this useful!