It is a widespread misunderstanding that a female cat must have had a nest before she can be castrated. But also early castration (for sexual maturity) is controversial. Partly because of the risk of not closing growth discs, which can lead to fractures (epiphysis), on the other hand, because of the adverse effects of anesthetics on the immature organs. We apply a minimum age of 10 months before our cats are neutered.
Sometimes too much weight gain can occur after neutering. This is especially the case in males, but both sexes should be limited in their food intake after the procedure because the energy requirement is reduced by 30%. This is something that the owner has to control. It is better to weigh the cat regularly and adjust the amount of food to body weight. Consultation with the vet about this is desirable.