I don't think there is a correct answer to this question.
Obesity is usually only a problem if the diet is too high in fat.
Even for adult birds, level of activity, molting, and other factors can influence how much food a bird needs. Mine eat more some days and less some days, and I've only ever had an obesity problem with one or two cockatiels in a community cage that ate too much seed mix. Weigh the bird periodically and handle it enough to know how the chest should feel at the proper weight. Then, if it starts to lose or gain weight, you will feel it in the chest and know to go to the vet or correct the diet. They lost the weight anyway.