How do I get my guinea pig to lose weight?

Decrease the treats. Some people will give their guinea pigs too many fruits. Fruits are high in sugar, which can lead to weight gain, and too many pellets can lead to weight gain. So cutting down and making sure you're not giving more than a quarter cup of pellets per day can help cut down on obesity. I heard that pellets are kind of like the French fries of their life. They like them, but it's not really good for them in mass, so you have to limit it.