Since guinea pigs are vegetarians and don’t consume much fat, it’s not common for your pet to become overweight. Weight gains can be indicative of a number of things, from a lack of exercise, to a few too many treats, to illness, and to pregnancy, which is why it’s advisable to weigh your guinea pigs during their health check. If your guinea pig is very overweight, then it may be having trouble moving around properly, and can develop painful sores on its feet. Once these are treated, you might want to put your guinea pig on a diet.
Keep giving them hay, but perhaps reduce their dry food intake slightly
If your guinea pig has stopped growing but is putting on weight, and you want to reduce this, then here are some ways to do so gradually. We don’t advise removing hay from your guinea pigs, as they really need this for adequate digestion. However, you may reduce the amount of dry food you give them to half a handful per day, and limit their fresh food to one cup of fresh vegetables.
Another good idea is scattering fresh food around your guinea pigs’ enclosures, so they have to run around a bit to get at it. Toys like balls and paper tents are also great ways to encourage your pet to be more active.